'85 250R top end carnage

[pismorat]

Not good as you can see. This is a .020" over piston, running a 39mm flat-slide Keihin carburetor, open air box, and run at sea level in the SoCal dunes. It is obviously running lean making the piston burn through, but what will cause this? I've been told wrong fuel mix, wrong jetting, or even leaking crank seals. I run Klotz Super Techniplate at 32:1, have a 55 pilot and 150 main jet, and don't know how to inspect the crank seals. The bike has run well for three seasons now, but over the past weekend...not so much. Any help is greatly appreciated since I'm trying to go back out in a month.

http://www.supermotors.net/getfile/1003564/fullsize/piston.jpg

[82 250r]

I've been told wrong fuel mix, wrong jetting, or even leaking crank seals.
That's about it...leaking head gasket or restrictive pipe/silencer as well.
Did someone put unmixed gas in it by mistake?

[yaegerb]

either lean or pre-detonation. What compression were you running in that motor?

Here is a good article on testing crank seals.

http://www.klemmvintage.com/airleaks.htm

[pismorat]

Thanks for the article. I never checked the compression after I rebuilt it after buying it (in pieces). It's never had straight gas in it and typically smokes out the pipe a bit...which is an FMF silencer with a massive expansion chamber. The cylinder is still good, so I think my plan is to check the seals, get a new piston and rings and then start from scratch on tuning it.

[Red Rider]

After a failure like yours, and looking at all of the debris that went into the center cases, splitting the cases to clean it all out is a definite must. Most likely the cylinder bore will need to be cleaned up as well.

[El Camexican]

Bad or old fuel perhaps. Were you on a top end run when it torched?

[82 250r]

splitting the cases to clean it all out is a definite must.
I agree...replace the lower crank bearing at a minimum... that gives you a chance to replace the main seals as well...hope it works out for you.

[threewheelin-feelin]

just a nice excuse to go with a big bore!!!

[Mosh]

150 main on a 39 mil carb is way too lean IMO.

I run 38 mils with ported engines and my mains range from 165-172 and they are a tad lean to keep the machines crisp. I dont do alot of high speed wot throttle runs.
I know everyone's stuff is different but I read all the time how guys are running 52-55 pilots in these big carbs with small mains. I have never had to run a 50 or larger pilot on a 250 based R with a 38 or larger carb. It sounds to me like guys are running lean up top an compensating rich on bottom to get rid of lean bogs coming on the main.

[barnett468]

yes, yes, yes and yes.

Here’s the deal as mentioned. All that junk went into your lower rod and crank bearings. They may or may not be damaged. Take your chances by not replacing them all.

When you switch from std gas to race gas you need to increase jet size by around 2.

Climbing a sand hill in the heat at wot will kill a bike faster than anything.

Here’s a pressure/leak down test video with the cheap leak down tool suggestions.

http://www.youtube.com/watch?v=zdq7NRcUIp8

What exactly were you doing when it happened?

Can you post photos of plug?

What is the number on your plug?

What is the elevation that you normally run your bike at?

What gas/octane exactly are you running?

Is your ignition timing stock or is it advanced?

Did you hear any pinging?

What was the outdoor temp?

Was the outdoor temp hotter than it has ever been when you rode it?

Was this the first time in the sand?

Here’s one plan of attack without having more info.



Fix what you are going to fix.

Install a 160 - 165 jet.

Run a 9 rated plug.

If ignition timing is advanced then return it to stock.

Do the crank case pressure test.

Do a compression test, if it is around 190 run like 100 motor octane gas, it its around 210 then run around 107 motor octane however if it is higher than 190 I would lower it by installing thicker head gasket or machining the head.

[pismorat]

Thanks for all the advice thus far! The fuel was fresh in the can that I added to fuel from 4 months ago in the tank. I was winding it up pretty good when it went. Answers to Barnett468's questions below:

What exactly were you doing when it happened? I was coming across the flats in 5th, about 3/4 throttle racing my wife back to camp...she won!

Can you post photos of plug? The plug is currently full of aluminum.

What is the number on your plug? Its a BR8ES.

What is the elevation that you normally run your bike at? I'm always right at sea level to 500 ft.

What gas/octane exactly are you running? I run 91.

Is your ignition timing stock or is it advanced? Stock timing.

Did you hear any pinging? No pinging that I know of.

What was the outdoor temp? It was about 70.

Was the outdoor temp hotter than it has ever been when you rode it? No.

Was this the first time in the sand? First time in deep sand with paddles, yes. But not first time in sand.

[barnett468]

ok good info

Ok good info, it looks this way to me, we’ll see what others think.

1. the only difference in the last 3 years is the addition of paddles and deeper sand, both these things put more load on the engine then you previously on flat terrain. This does not mean that it was more load then previously when you might have been going up a hill with non paddle tires so hard to say if the paddles and deeper sand did you in.

2. if it was due to an air leak then it would have idled noticeably higher and/or more erratically than before unless it happened to get the air leak while you were riding but we will likely never know so I would do to what I mentioned earlier.

Also if this is the first time you have ridden it like this for this long it is best to run a richer oil/gas mix and jet up 1 size with the richer mix.

Your prob was not caused by lack of oil.

[barnett468]

post correction

i have no edit button.

Also if this is the first time you have ridden it like this for this long it is best to run a richer oil/gas mix and jet up 1 size with the richer mix if you plan on doing this again.

[RIDE-RED 250r]

It's a little hard to tell in your pic. But usually with a burn-down due to a lean condition you will see the exhaust side of the piston crown has been eroded away.

That looks more like a failure due to detonation to my eye. However, it's odd that you didn't notice any pinging or knocking prior to the burn-down...

I have also seen similar damage due to burning excessive amounts of coolant on diesel engines. I have not yet experienced it with a 2-stroke gas engine. Any chance you can see if there are signs of a bad head gasket allowing coolant in??

I wholeheartedly agree with other advice given to replace crank bearings and seals. And at minimum have the crank assembly checked thoroughly for damage/wear.

[MTS]

You happen to pull your carb apart yet? was that the first Close to WOT run.. this time around when it happend?

[Dirtcrasher]

Looks like classic detonation to me also. Pinging isn't the easiest thing to hear in the world. I'd tear it all down and you may even have to have the rod and big end bearing replaced.

Just DON'T forget what allot of others do. Use the service manual and look at the taper on your crank. Then you'll see why they want the left side crank seal set in another 5mm's from flush.......

[ChrisD]

That is definitely detonation. You probably didn't hear the noise. That happened to me while trying to tune a motor on alky. It can happen fast.

Time for a crank and bearings.

[pismorat]

Thanks for all the help. Here's a better shot at the ext. side of the piston. I plan on doing a full teardown now due to all the suggestions. I can see a problem with splitting the cases...that bolt in the bottom of the picture is stuck good. Don't know if the cases come that way stock or if the P.O. did that to clear the larger pipe, but with it notched like that it is full of debris. Upon rebuild, what can I do to keep it from detonating? Is that a larger jet, stronger full mix that'll cure that? This also wasn't the first WOT run of the trip, but probably held WOT longer than previously.
http://www.supermotors.net/getfile/1003606/fullsize/piston2.jpg

[KASEY]

that notch in the cases is factory,,

[RIDE-RED 250r]

Certain year cases were notched like that. Later ones were not.

As to preventing detonation on the new rebuild. Make sure and use OEM gaskets or at least OEM thickness gaskets. Head and base gasket thickness aren't always the same with aftermarket stuff and those 2 gaskets will have a direct influence on compression. According to my Honda factory service manual, a stock R should be a little north of 190psi compression. Knowing your compression numbers will get you close, but checking your un-corrected compression ratio (UCCR) will tell you for sure. For this you need to determine your cylinder head capacity and capacity between the top of the piston at TDC and the tops of the cylinder deck. I would use the search engine to seek out the exact procedure for determining the UCCR.

It makes sense that the detonation would cause a failure on a longer WOT run as compared to running around a little easier. When you run her hard like that, combustion chamber temps climb to their highest, and too high of a compression ratio for the fuel you are running will result in what you had happen.

FYI: My service manual states that a stock 250r should have 92-100 octane fuel run in it. That doesn't allow much room for error with your fuel as most regular fuel stations only offer up to 93 octane. One of my R's is stock as far as compression ratio and I run a 60/40 blend of ethanol free 91 with 110. It's probably not necessary to run at 60/40 but I would rather play it safe and have a little margin for error. Plus the station where I get my race fuel doesn't sell it in half gallon increments.

I have heard/read more times than I can count that fuel rating was different back then compared to now and I don't know what to believe. So, I do what I do to play it safe. I like to ride my machines, not rebuild them every other day.

This is the general rule of thumb... Once you get your engine put back together, if you have more than 200psi compression, you should be running a blend of race/pump fuel.

[Mosh]

Here is how to get the bolt out. I have had to do many.

Get a torch set on low. Heat the threaded end of the bolt and apply light heat in the notch area of the case. What siezes the bolt is the cruddy oil from exhaust flange leakage. You will see that crusty oil start to soften and bubble. Get the center of the bolt at the cases just barely glowing red. DO NOT HEAT THE CASE. Work back and forth with the torch on low at the threaded end and in the center heating evenly. Then get a impact and put it on the bolt side once you see the old crusty stuff bubbling some and lightly try to spin the bolt with short burst of the impact. Dont hold the impact wide open. It is the shock of on off trigger pull that will loosen the bolt. Try to get the bolt spinning by using both directions of the gun. Once you do that it should come out with a punch and hammer. Also if you have good aim, a airhammer with a punch bit will drive it out too, but you will still have to use some heat to get the hardened exhaust crude to loosen.

There is a difference between "detonation" and "pre-ignition" and often they are both grouped in the same failure. I won't get into the specifics as there are several articles explaining the differences on google. Your engine appears to have suffered from pre-ignition. This is caused by hot spots in the chamber which generally are a result of poor cooling system operation or lean situations, or improper ignition timing, or a loose spark plug or wrong heat range plug, which your were running factory plugs.
Detonation can be heard and generally does not burn through the top of the piston.
So I stick to my assessment that you were way lean on the main, which results in not enough fuel to keep the piston cool at higher RPM's. The the top of the piston starts to get hot which pre ignites the fuel mixture before top dead and the resulting hole in the center of the piston is the final result.

Engines will run for a long time with detonation. Pre Ignition will start fast and exponentially get worse second by second. The result is very fast, and very catastrophic like you see with your engine.

Rebuild the top and bottom end, Including a new rod, Run a minimum of 92 octane with your 32-1 mix, and drop your pilot to a 48 and move your main to a 172-175 to start with the needle in the middle.
You should be safely rich at those numbers. Break it in for a few hours, then you will feel the top end being "dirty" like a fouled plug coming on the main. Then try lowering your main to clean it up so it does not feel loaded up when going WOT. Remember this..On a 2 stroke, if that thing wants to rev out really good on the top end, FEAR LEAN. GO Rich with the main until it burbles or feels like it is loading up, then back down one size and fine tune with the needle.

These are just general guidelines, but trust me..You were WAY too lean with a 150 main on a 39 mil carb. Your altitude is much the same as mine and a 150 main is suicide here.

[barnett468]

that bolt in the bottom of the picture is stuck good.if you don't have a torch as suggested by mosh you can simply put a pair of long wrenches on it and turn. it will either come off or it will snap in which case you simply get another from the hardware store. udse a grade 8.




Upon rebuild, what can I do to keep it from detonating?read my previous post. since you have been doing close to the same thing with it for the lat 3 years i suggest the same as i did earlier. you do not need any big changes, just several different small ones but i suggest you do not skip any of them. they can easily be changed after you run it to see how it goes.

take a photo of your timing marks before removing the timing plate and post it for us. you must know exactly where it is before you remove it. also mark where it is with a scratch. it is very sensitive to timing.
if you are going to ride it like this again go 24 - 1 or 20 - 1

install a 165 main then do a plug reading.

retard the timing by the thickness of the timing mark which is around .007" wide. this is a change i would likely make permanent based on your current info. the photo of the timing plate will help determine this.

run the octane ratings i suggested.

use a cooler plug, in your case a 9.

[Mosh]

Barnett, Water cooled 250R's do not have adjustable timing plates like a Tecate or Tri-Z unless they have been replaced with aftermarket or someone put one of those plagued offset timing wood-ruff keys in there,timing would be stock. The trigger coil is fixed separately on a non adjustable plate and cannot be advanced or retarded unless it has been modified or replaced with aftermarket stuff.

[barnett468]

Barnett, Water cooled 250R's do not have adjustable timing plates like a Tecate or Tri-Z unless they have been replaced with aftermarket or someone put one of those plagued offset timing wood-ruff keys in there,timing would be stock. The trigger coil is fixed separately on a non adjustable plate and cannot be advanced or retarded unless it has been modified or replaced with aftermarket stuff.Ok Mosh, thanks for the info. I guess that's just as well. Goes to show just how much a Kawi guy knows, lol.

Happy thanks giving to you, Mrs. Mosh and everyone else.

[RIDE-RED 250r]

Not disputing your info and assessment Mosh, but wouldn't a lean burn down be evident by pretty severe erosion of the exhaust side of the piston crown along with the hole in the piston? I have had sleds do that due to losing a crank seal. Had exhaust side of the piston crown severely eroded but no hole. Maybe it can vary a little bit and if severe enough seize up before the hole developes?

[Marty]

I know it will be expensive and tedious but do it right you will be happier with end result have your crank checked for any twisting, replace all your bearings and seals with honda OEM parts, have a good machinist that you are comfortable with do bore and hone with piston that will be used, have your head checked for squareness, buy or use an OEM 1985 Honda ATC 250R head gasket and base gasket and once your engine is ready for install PLEASE do a LEAKDOWN TEST and make sure you or yourself does test do not trust anyone unless it is done in front of you.
And once engine installed jet accordingly to the conditions and temperatures you ride in or at good luck.

[JasonB]

I bet she ran strong right up until the melt down though!! Lean is MEAN until she burns lol

Just make sure you do a compression and a leak down test before you run it again, that will eliminate more running headsChes. Otherwise lots of solid info in here

[Mosh]

Not disputing your info and assessment Mosh, but wouldn't a lean burn down be evident by pretty severe erosion of the exhaust side of the piston crown along with the hole in the piston? I have had sleds do that due to losing a crank seal. Had exhaust side of the piston crown severely eroded but no hole. Maybe it can vary a little bit and if severe enough seize up before the hole developes? Anything could have happened. Quite possible his engine was detonating as well. That is why I said both terms are often grouped in the same failue. Regardless It is pretty evident that this engine was severely lean and it is a bet any tuners or builders that see that will agree with that knowing the main jet is a 150.

But I digress. Its obvious that he needs to start over with this engine.
Looking back at the most recent pic also I noticed it does indeed look like someone actually ground those cases and there may even be a crack. Hopefully that is just a smear of grease on the left side of that center area.

[El Camexican]

I had a single piston melt through dead center once on a 4 cylinder 2 stroke. The other three were fine and there was no discernible wear or damage anywhere else on the piston. Never did figure out why and it never happened again and by no means did it happen during a run that was more taxing than any other the engine had lived through.

In my case I suspect something blocked the main jet of that one carb, but in your case I suspect it was as has been pointed out by others the combination of a main jet that was too small, sand paddles and perhaps that 4 month old fuel mix degrading the new fuel you put in.

Like as been said in many of these posts, rebuild it (with a forged piston), check your reeds, make sure your cooling system is working (when you fire it back up), clean the carb, put in whatever Mosh suggested for a main jet, make sure you have the right plug and use fresh fuel when you ride. Pre-mixed fuel degrades faster than straight gas. I dump any fuel in my bikes that is over 2 months old and feed it to my wife’s car, it’s not worth the risk.

BTW, are the paddle tires larger in diameter than the others you have? If so you may want to gear down (one tooth less on the front is the cheapest way) when you use them as pulling a larger tire would exacerbate any pre-ignition or detonation that might happen.

[barnett468]

This is part of my experience with many seizures and holes in pistons, others may vary.

LEAN JETTING

A lean condition will typically cause the piston to seize before it puts a hole in a cyl unless the piston is extremely loose in the bore. I have actually never put a hole in a piston [just lucky I guess] but have seen several on both 2 and 4 strokes. I have seized plenty of holes and eroded domes though and seen plenty seized, lol.

A lean condition can contribute to detonation.


DETONATION

Even a bike that is jetted perfectly or jetted rich can still detonate or have pre ignition especially if the octane rating is too low for the compression and/or the timing is too far advanced and/or the plug rating is too hot and/or if there are sharp edges in the combustion chamber that can get hot enough to ignite the gas without a spark etc.


DETONATION/PISTON EROSION

Unlike a piston seizure, detonation is a cumulative process. It can cause a hole in 30 seconds or might take 3 years of riding. It typically erodes small bits at a time, sometimes slowly, usually fairly quickly.


CAUSE OF MELT DOWN

He has been riding this same setting with the exception of the tires with no prob for 3 years. There is a high probability it was pinging loud enough for most people to hear it but it typically takes a trained ear to understand what they are hearing and understand what the sound means.

I know for a fact that there are plenty of yahoos out there at Glamis on thanksgiving wringing their bike out at wot in first gear etc,. or running it up a hill with it pinging so loud the people at the bottom can hear it but the happy hamered rider is totally oblivious to everything except who’s gonna loose the race to the top and have to buy the next beer.

Irregardless of whether the hole happened quickly or over the last 3 years, my guess is that lean jetting contributed to the prob but that it was caused more by high compression and/or improper squish clearance and/or angle on the cyl head and not enough octane to compensate for the high compression. Also too hot of a plug for the overall conditions. My guess is based on the premise that he had no more than .004” cyl to piston clearance and that his ignition timing is stock.

[barnett468]

post correction

"I have seized plenty of holes and eroded domes" should read "I have seen plenty of holes and eroded domes"


Sorry, I have no edit button.

[Dirtcrasher]

Were you bad and the mods took it away?? :lol:

Am I stupid? never mind, skip that question. Why is there what appears to be sand all over the piston, in the rings etc etc.??

[barnett468]

Were you bad and the mods took it away?? :lol:Am I stupid? never mind, skip that question.and just when i was starting to like you, lol. i actually have no idea why they took it away but no need to dwell on that. i had one at first, then it was removed after about 6 weeks. i had no idea what happened to it until about 3 months ago when i asked Mrs. Mosh, who seems to be very nice, what happened to it, and she said that howdy removed my access to it but did not say why. seems kinda weird to me but ok, it just means more unnecessary posts from me when i need to add or make corrections to one i just posted, lol.




Why is there what appears to be sand all over the piston, in the rings etc etc.??lol, that my friend is aluminum that has disassociated itself from the dome of his piston.

[El Camexican]

So it's a sand cast piston?

[pismorat]

The piston was a ProX cast piston. There appears to be sand all over it because I knew it was coming down no matter what, so I popped the head off out there in my trailer while there was a downpour. Gave me something to do. I buttoned it back up loosely and then got it to this point at home in my garage. Some of the water/coolant leaked in on the drive home, but as I said...I knew it was coming down. I'm getting the alternator puller tomorrow, so at that point I can get it all the way down for bearings, seals, and inspection. Should I go with a forged Wiseco over the cast piston?

[barnett468]

GUESS I NEED A BIGGER COMPUTER SCREEN, DOESN'T LOOK LIKE SAND ON MINE, LOL.

Unless your bike is ported for high revs and you run it wot all the time a stock orig piston is fine imo. i would not use an aftermarket cast piston.

the wiesco forged are a bit of added insurance and for the cost of an orig honda piston it migh cost the same.

[barnett468]

since you say you rarely run at top end or wot for long your carb might be a bit big also, you might consider a 36 mm.

[El Camexican]

Copy pasted from an another site:


CAST VERSES FORGED
This is an age-old problem for engine designers. At what sort of power level is it necessary to change from a conventional cast Eutectic/Hypereutectic piston to a forged item? According to ACL's chief piston engineer, the only real disadvantage of a cast piston (in high output situations) is in the case of a piston failure, a cast items is more likely to shatter and damage the engine, as a whole, more than a forged piston. A big advantage with forged pistons is they generally result in a more ductile material, with the effect being the piston can take a higher level of detonation before failing.

It is my understanding that a well tuned 2 stroke will be subject to some level of detonation in its life. If this is true then why would anyone want a cast piston in their engine? I have never, ever, not even in a car engine rebuilt with cast pistons. Yea the forged slugs rattle a little when cold, I could care less. What I care about is not having to worry about cracking a slug when I lay on an engine.

[barnett468]

It is my understanding that a well tuned 2 stroke will be subject to some level of detonation in its life.according to harry klems deto sensor this is correct, he also says that a certain level of deto is expected and acceptable in a high perf 2 stroke. this being said, if your bike has a lot of deto it is not properly tuned and should not be run like that.



If this is true then why would anyone want a cast piston in their engine?I agree but the proof that they work fine is in the puddin.



I have never, ever, not even in a car engine rebuilt with cast pistons. Yea the forged slugs rattle a little when cold,Not so much anymore with some using new materials and mfg processes.



What I care about is not having to worry about cracking a slug when I lay on an engine.Here's a short list of just a few Kawi factory cast piston users. granted, they did get a new piston after every day of racing however Kawai was not strapped for cash. if they thought a cast piston might fail they would not risk a championship on using one.

jimmy white multiple series champion

jeff ward multi national and supercross champ

brad lackey national and world champ

gary semics national champ

jimmy weinert national champ

mike kiedrowski national champ

jeff emig national champ

mike larocco national champ

ricky carmichael national champ

around 100 mini national championships.

myself with over 700 motos and practice sessions on many different types of bikes.


ok my finger hurts from all this typing so i guess i'll stop now.

[El Camexican]

according to harry klems deto sensor this is correct, he also says that a certain level of deto is expected and acceptable in a high perf 2 stroke. this being said, if your bike has a lot of deto it is not properly tuned and should not be run like that.


I agree but the proof that they work fine is in the puddin.


Not so much anymore with some using new materials and mfg processes.


Here's a short list of just a few Kawi factory cast piston users. granted, they did get a new piston after every day of racing however Kawai was not strapped for cash. if they thought a cast piston might fail they would not risk a championship on using one.

jimmy white multiple series champion

jeff ward multi national and supercross champ

brad lackey national and world champ

gary semics national champ

jimmy weinert national champ

mike kiedrowski national champ

jeff emig national champ

mike larocco national champ

ricky carmichael national champ

around 100 mini national championships.

myself with over 700 motos and practice sessions on many different types of bikes.


ok my finger hurts from all this typing so i guess i'll stop now.

If you want to spend your Sunday convincing a guy who just experienced a catastrophic CAST piston failure to buy another cast slug be my guest, but don't use examples of guys whose bikes weigh next to nothing and are tuned by the world's best AND actually see a benefit from a lighter cast unit VS the heavier forged piece as a reason to do so. You also made references earlier in this post to having seen plenty of holes and eroded domes, can we assume based on your vast time and experience with Kawasaki that those were all cast pistons that had failed?

[barnett468]

If you want to spend your Sunday convincing a guy who just experienced a catastrophic CAST piston failure to buy another cast slug be my guest, but don't use examples of guys whose bikes weigh next to nothing and are tuned by the world's best AND actually see a benefit from a lighter cast unit VS the heavier forged piece as a reason to do so. You also made references earlier in this post to having seen plenty of holes and eroded domes, can we assume based on your vast time and experience with Kawasaki that those were all cast pistons that had failed?

unlike some others, i prefer to read and try to understand someones post before making comments about it. below is a portion of my post 36.
the wiesco forged are a bit of added insurance



1. i for one fail to see how my comment above can possibly be interpreted by ANYONE as ANY type of attempt whatsoever to convince him or anyone that a cast piston is better in any way than a forged one or that he should buy a cast one instead of a forged one. your comment clearly suggests to me that there is in fact at least one person that can interpret it differently than i intended it to be understood and that person is you.

2. his piston is not an oem piston and appears that it is not made in japan or the us and in my fairly vast experience with pistons and products from some particular countries they are inferior to us and japanese made items.

3. this being said, imo it is blatantly obvious to anyone with extensive experience in this area that the appearance of his piston strongly suggests that not even a forged one would have survived whatever caused his piston failure.




You also made references earlier in this post to having seen plenty of holes and eroded domes, can we assume based on your vast time and experience with Kawasaki that those were all cast pistons that had failed?

1. first of all i for one prefer not to assume anything.

2. i can answer your question with one word which is no.

3. i will expand on that for you and say that i have not only seen holes/erosion in forged pistons but have also seen some that shattered into lots of tiny little pieces from deto or pre ignition and other non impact causes.




actually see a benefit from a lighter cast unit VS the heavier forged piece as a reason to do so.

1. Actually there are many forged pistons that are FAR lighter than a cast one.

[barnett468]

If you want to spend your Sunday convincing a guy who just experienced a catastrophic CAST piston failure to buy another cast slug be my guest, but don't use examples of guys whose bikes weigh next to nothing and are tuned by the world's best

1. ok, heavier bikes that are likely subjected to far more extreme conditions than his ever will and not tuned by the worlds best.

jimmy white, chris white, donnie luce. they sall used cast pistonsd as i already mentioned on jimmys bike in my previous post but none were tuned by the worlds best anything. either they tuned their own after klemmbuilt their engiunes or they were tuned by team green mechanics who were reasonably knowlesdgeable but certsainly not the worlds nbest by sany stretch of the imagination.

2. OTHER HIGH PERF BIKES WITH CAST PISTONS AND MINIMAL FAILURES - This would be every single tecate ever made including the 4 wheel ones. You see, kawai has a warranty dept that was around 200 feet from all 4 of my work areas and we talked all the time and it was there job to notify me specifically if they had an unusual number of warranties. since they never told me about even 1 single piston or rod failure regarding tecate's they simply did not have enough to consider the anount out of the ordinary.

[barnett468]

oh el camexican, sorry but i forgot to mention the holland beach race that jimmy and donnie went to that they rode at wot the entire race in 2 foot deep sand using stock cast kawi pistons with 0 failure.

[82 250r]

It is my understanding that a well tuned 2 stroke will be subject to some level of detonation in its life.
If any motor (2 or 4 stroke) is detonating, then it is not well tuned and/or well designed. Many riders run on the edge of lean, edge of over-advanced timing, edge of over-heating, etc without detonating. Once you go over the edge, then the problems begin.

Piston choice has nothing to do with detonation. If the cause of detonation is not corrected then the same result should be expected regardless of cast or forged.

IMO, cast pistons seem to heat up more consistently with a cast cylinder.

The Issue seems to be a very lean main. It appears the OP's piston has been burning for a while and finally gave up the ghost on this ride.
Not the end of the world, just a good excuse to replace all bearings/seals and get a fresh top end.
You'll love it when you're done.

Marc

[El Camexican]

If any motor (2 or 4 stroke) is detonating, then it is not well tuned and/or well designed. Many riders run on the edge of lean, edge of over-advanced timing, edge of over-heating, etc without detonating. Once you go over the edge, then the problems begin.

Please see below.

Detonation Management – The Key to 2stroke Power and Reliability

a technical paper by Harry and Gerhard Klemm of Klemm Vintage Racing Engines



Overview - For many decades, professional race engine builders have believed that the best racing engine setups where those that can operate consistently on the brink of detonation, without ever crossing the line of going into detonation…. And time has proven that they were half right. Modern data gathering tools developed during the 1990s showed clearly that the best racing engine setups actually detonate 5-15% of total combustion strikes. These same tools allowed engine builders to learn what the detonation tolerance level of any particular engine was (it varies from one engine design to another), and helped them develop tuning tactics that reduced detonation risks without reducing power output. These tools forever changed the way engine builders went about seeking additional power, and forever removed the specter of random detonation related engine failures for racing 2strokes. In short, it was the ultimate game changer in the assured reliability of racing two stroke engines.

[82 250r]

...and forever removed the specter of random detonation related engine failures for racing 2strokes. In short, it was the ultimate game changer in the assured reliability of racing two stroke engines.[/I]
I agree...that's essentially what i posted.
The goal is to " forever removed the specter of random detonation". There's a reason for that...Detonation is bad.

My point is that detonation can be eliminated through modern engine design and tuning techniques...no amount of detonation is acceptable without risk.

Marc

[El Camexican]

unlike some others, i prefer to read and try to understand someones post before making comments about it.

Oh if only that were true...

It has been more than once that I have seen you respond in a belittling manner to a post you didn’t even take the time to comprehend before contradicting, often responding with information totally unrelated to the topic when confronted about it. While I’m at it I should point out that I find it extremely rude when you reply to a post response that you agree with, but add some other detail to make it appear that while the original poster was right (in your option) you were MORE RIGHT because you were aware of some famous guy it happened to and while not necessarily rude, your constant reminders to posters that you were right about something, or that someone posted the same suggestion as you did two weeks earlier reeks of some sort unfulfilled need for acknowledgment. If a poster garnered something useful from your post perhaps they will thank you, if not life goes on, don’t demean yourself by acting like you should be getting a trophy.

I’ve said about all I have to say here, so please do me a favor, when we run into each other in a post please respond directly to the poster’s question, not my response to him and in return I will do the same. Oh, and please don’t PM me to complain about how rude or ill-informed someone is, I’m not interested in having that conversation.

[El Camexican]

I agree...that's essentially what i posted.
The goal is to " forever removed the specter of random detonation". There's a reason for that...Detonation is bad.

My point is that detonation can be eliminated through modern engine design and tuning techniques...no amount of detonation is acceptable without risk.

Marc

Agreed, but this guy has an engine from the mid 80's, so unless he’s getting his combustion chamber reshaped, or running 114 fuel his engine will likely be subject to detonation at some point and would (In my opinion) be better served to have a forged piston in it.

[82 250r]

Agreed, but this guy has an engine from the mid 80's, so unless he’s getting his combustion chamber reshaped, or running 114 fuel his engine will likely be subject to detonation at some point and would (In my opinion) be better served to have a forged piston in it.
I disagree.
Proper engine building in 2013 is not a mystery...even Japanese engineers from the 80's had it figured out.
Can you improve upon that? Yes.
Will you burn a hole in your piston if you don't? No.

The OP does not need to reshape his chamber, run race fuel, or install a forged piston...he needs a bigger main.

I have 2 engines from the mid 80's...they do not detonate...one is bone stock.



Marc

[El Camexican]

I disagree.
Proper engine building in 2013 is not a mystery...even Japanese engineers from the 80's had it figured out.
Can you improve upon that? Yes.
Will you burn a hole in your piston if you don't? No.

The OP does not need to reshape his chamber, run race fuel, or install a forged piston...he needs a bigger main.

I have 2 engines from the mid 80's...they do not detonate...one is bone stock.



Marc

If you are so confident in that statement why don’t you respond to his original question by telling him to buy a cast piston instead of arguing about it with me?

[82 250r]

My friend, I'm not arguing with you...we're on the same team in regards to helping the OP.

IMO, installing a cast or forged piston is not the issue... finding and correcting the source of detonation is.

Marc

[El Camexican]

My friend, I'm not arguing with you...we're on the same team in regards to helping the OP.

IMO, installing a cast or forged piston is not the issue... finding and correcting the source of detonation is.

Marc

That I can agree with. I hope you don't think I am suggesting that this happened because he didn't have a forged piston. All I am saying is that a forged piston is the way I'd go on the rebuild.

[nstyle73]

I think he needed to check his compression ...........but its too late for that.

[barnett468]

Oh if only that were true...

It has been more than once that I have seen you respond in a belittling manner to a post you didn’t even take the time to comprehend before contradicting, often responding with information totally unrelated to the topic when confronted about it. While I’m at it I should point out that I find it extremely rude when you reply to a post response that you agree with, but add some other detail to make it appear that while the original poster was right (in your option) you were MORE RIGHT because you were aware of some famous guy it happened to and while not necessarily rude, your constant reminders to posters that you were right about something, or that someone posted the same suggestion as you did two weeks earlier reeks of some sort unfulfilled need for acknowledgment. If a poster garnered something useful from your post perhaps they will thank you, if not life goes on, don’t demean yourself by acting like you should be getting a trophy.

I’ve said about all I have to say here, so please do me a favor, when we run into each other in a post please respond directly to the poster’s question, not my response to him and in return I will do the same. Oh, and please don’t PM me to complain about how rude or ill-informed someone is, I’m not interested in having that conversation.


My posts here, are in fact, for the benefit of the op, since they had some level of relevance to his problem and selection of piston choice. Just because I might on occasion use your quotes and/or someone else’s, in no way means that I am replying to you or those that I am quoting. It’s assumptive on ones part to think I am imo.


I am interested in only one thing, which is helping an op by posting the most accurate info I personally know of. I would hope that this is everyone’s goal since it is my understanding, as inaccurate as it might be, that this is the primary purpose of this particular forum/section of the site. If I see an obvious inaccuracy in any info, I, like many others here, including YOU, from what I have seen may on occasion correct [or try to correct] an inaccuracy that I, they, or you see. Some members do it on almost a daily basis. Your post quoted above suggests to me that in your eyes I should be prohibited from doing so.


Your quote below which is also from this thread and directed to 82 250r also suggests to me that you are unnecessarily abrasive to others without justification also. It also suggests to me that anyone that argues/debates or otherwise might have a different opinion/viewpoint and/or had a dufferent experience than you in a particular situation or with a particular product that they are wrong.


If you are so confident in that statement why don’t you respond to his original question by telling him to buy a cast piston instead of arguing about it with me?


My posts here, are in fact, for the benefit of the op, since they had some level of relevance to his problem and selection of piston choice. Just because I might on occasion use your quotes and/or someone else’s, in no way means that I am replying to you or those that I am quoting. It’s assumptive on your part to think I am imo.


I am interested in only one thing, which is helping an op by posting the most accurate info I personally know of. I would hope that is everyone’s goal since it is my understanding, as inaccurate as it might be, that this is the primary purpose of this particular forum. If I see an obvious inaccuracy in any info, I, like many others here, including YOU, may on occasion correct an inaccuracy that I, they, or you see. Some members do it on almost a daily basis. Your post suggests to me that I am the only one in your eyes that does this and that at least I should be the prohibited from doing so.


Your post also contained a question, and since it was NOT directed to any particular person, I replied to that question in my next post which also contained additional info relevant to the ops problem. My reply to your question was followed by more questions from you that were aimed directly at me. I simply replied to those questions with the info you requested.


You also “told” me in what I perceived as a moderately abrasive comment, the following:


don't use examples of guys whose bikes weigh next to nothing and are tuned by the world's best
I replied to that comment/demand by posting the info your post suggested to me you wanted, in the quote pasted. Now you appear unhappy that I answered that and the other questions you asked me and also that I complied with your demand.


1. ok, heavier bikes that are likely subjected to far more extreme conditions than his ever will and not tuned by the worlds best.
1. jimmy white, chris white, donnie luce. they all used cast pistons as i already mentioned on jimmys bike in my previous post but none were tuned by the world’s best anything. either they tuned their own after klemm built their engines or they were tuned by team green mechanics who were reasonably knowledgeable but certainly not the world’s best by any stretch of the imagination.

2. OTHER HIGH PERF BIKES WITH CAST PISTONS AND MINIMAL FAILURES - This would be every single tecate ever made including the 4 wheel ones. You see, kawai has a warranty dept that was around 200 feet from all 4 of my work areas and we talked all the time and it was there job to notify me specifically if they had an unusual number of warranties. since they never told me about even 1 single piston or rod failure regarding tecate's they simply did not have enough to consider the amount out of the ordinary.


For some reason you continually challenge my info which includes my suggestion to use flammable brake cleaner to the difference in the amount of kick back between a 450 cc maico and a 1200 cc 4 cylinder street bike and now to pistons etc.. I don’t mind this at all providing it is done in a courteous and respectful manner. My perception is that in most cases when you resoond to something have posted it is frequently done with some level of abrasiveness which I feel is unwarranted. In each of those cases as well as any others I have replied with 0 sarcasm and abrasiveness providing I did was not unnecessarily attacked.


My replies are direct and to the point. I am an engineer as you and many here well know and my experience with engineers in general is that their answers to questions often seem “dry” and might be interpreted by some non engineer type people that are “sensitive”, to sound “snobby” or have a better or smarter than thou attitude.


To hopefully put some people’s minds at ease, this is not my intent, nor any other engineer’s intent. Engineers deal in facts whenever possible and best guesses if necessary based on as much information that they have at a particular time. I, as well as other engineers I know, quickly acknowledge if they make an error in their info and not only readily accept being informed of it and supplied with the correct info but they are also grateful because it is every good engineers desire to have accurate info and they have a passion to learn as much as possible about their particular field etc. It is every engineers fear to make a mistake in their engineering and have a frame crack in half and possibly injure or kill someone. Even in the ATV world engineers have an extremely heavy burden on responsibility especially due to the severe conditions the off road bikes are subjected to. Engineers ask lots and lots and lots of questions.


The steering head snapped clean off both jeff wards and roger decosters bike in races and could have easily resulted in serious injury like what happened to danny chandler who ended up being a paraplegic from what appeared to be just a minor crash as his friends watched on in horror and disbelief.


This was not only an engineering failure but might also have been the failure of the mechanics since this might have developed as a small crack which should have been noticed by the mechanic during their mandatory routine frame inspection before it got put if hand.


There are many people here that know quite a lot about bikes and EVERYONE knows something about some subject that I and others do not. I, in no way, think I know it all. I too have learned from others here.




Unbeknownst to you, I have had productive dialog with one of the mod’s here regarding people that make off topic posts that are directed at me that I perceive as being unwarranted, unprovoked, abrasive and/or disruptive to the site and I will follow that mod’s instructions which is to report them to that particular mod. Therefore since this is how I perceive your post I am going to report it to them. This is not my preference but since I have been instructed to do so and they are the ones that run the site this is what I will do in this case and from here on out.


You may be unaware of this but they recently banned 2 long time members for posts that I think the mod’s perceived as having an unnecessary level of abrasiveness directed towards another. I was also told by a mod, that some members seem to be able to bash at least some of the mod’s and do so with impunity. I do not know for certain but since the recent ban of the 2 members I referred to, I’m only guessing that the level of tolerance for this type of thing has been reduced.




Dear Pismorat and others;

I sincerely apologize for this detour and if you do not feel that my info has benefited you at all or you no longer want me to post on your thread please feel free to tell me so, after all it is your thread, not mine or anyone else’s.


Regards;

Barnett468

Kawasaki project engineer and head of Kawasaki ATV R and D department in the 80’s.

[JasonB]

181632




lol