'85 250R top end carnage

[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??

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?? 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.