1986 Tri Z Top End Help

[nstyle73]

I do not usually post questions, especially about engines, but I'm at that point. So far I have been lucky enough that everything I took apart ran when I put it back together. I have had issues, but they always ran. My luck has ended. To make a long story short, a simple base gasket replacement led to a fresh bore on a completely stock 86 Z. 1st bore to 68.25mm by a reputable local shop that I have had bore several cylinders in the past without issue. The piston is a Wiseco 515P1 marked "0.25mm" with 515P1 on the top as well. The rings are marked "N25".

I put the bike together and it fired once and I have not been able to get it to start. Nothing else on the bike was touched and the bike is completely stock. The bike ran fine before teardown, just had a leaking base gasket and a leaking exhaust flange. I have spark, and swapped plugs to check. I also believe that the fuel pump is working as there is some fuel in the cylinder when looking in with the pipe removed and I also checked fuel flow out of the pump by kicking it over. Compression before with the stock piston was 150psi cold. I noticed the piston and rings didn't appear to match so I borrowed a dial indicator and the cylinder ended up being slightly out of spec for roundness so I had it bored to 1st over. After it didn't start today, I checked compression at only 140psi cold. I had replaced the head and base gaskets with new Cometic ones, torqued to the values I found in my 250r book ( I don't have a Z manual and this is the first Z I have had apart with a problem)

I pulled the cylinder again, the piston seems to fit the cylinder acceptably by hand as I don't have a dial indicator handy, but the ring end gap is .025" which seems a touch excessive. When I pulled it apart the first time on the original bore, it was running the stock piston with OEM rings marked 'K" which I now believe to be 1st over rings as I have a set of 68mm OEM rings that are marked "N" Any help on the ring end gap or other suggestion would be appreciated. Its disappointing because the base gasket leak wasn't that bad.......

[El Camexican]

Grab the overflow tube at the handlebars and blow into it. That will prime your carb. It should fire. If not, pull the plug and spray some WD40 in the cylinder and kick it over. If it has spark it will fire.

.025" on the rings is where I'd be changing them, but you should still be able to start it. After that I'd tear it down and get everything measured properly.

[Mosh]

I have had Z engines twist the flywheel on the key after rebuilding the top end while kicking it repeatedly trying to get the fuel system to prime up with the new cylinder.
You may want to remove the flywheel for inspection especially if it is backfiring air out the pipe loudly while kicking, or trying to slam the kicker up into your foot while starting.

[nstyle73]

I may check that, but it doesn't seem to have those symptoms. I hadn't even drained the carb bowl, just slid it back after I pulled the airbox tube off because I was unsure of what it would take to prime the pump. The end gap on the brand new rings and somewhat low compression is what concerned me most. I checked them before I installed them the first time and thought it was a little big but only had Tecate and 250R specs to compare to. I have it apart so I will probably see about getting everything measured before I attempt putting it back on. Pulling the flywheel won't take too long either. Thanks for the info.

[barnett468]

Hello nstyle73



PISTON/CYLINDER CLEARANCE – Should be .0024”-.0026” per manual. Since you do not have a measuring device you can estimate the clearance by doing the following.

1. Tear a piece 3” X 1/2” from std issue lined school paper.

2. Install 1” of it into the bottom of the cylinder on either the intake or exhaust side.

3. Install CLEAN DRY piston into bottom of cylinder making sure the arrow on top of it is facing forward.

4. Stop when bottom of skirt is flush with bottom of cyl.

5. Try to remove paper, if it tears it is too tight, if it pulls out with very minor effort is correct, if it pulls out easily it is possibly slightly loose in which case proceed to next step.

6. Fold paper in half, install open ends 1” into cylinder.

7. Install piston until bottom of skirt is flush.

8. Try to push piston past paper, if it does not push past paper with moderate effort it is not excessively loose, if it pushes easily it is way too loose.



RING END GAP - Your ring end gap should be .014”-.020” max per manual. See OEM manual at link below.



COMPRESSION - Should be around 160 plus or minus 10 psi, check manual to reconfirm. It might be a little low until rings seat. Compression gauges vary in accuracy.



OEM MANUAL CLEARANCES PG l3-15

http://www.oscarmayer.net/atc/manuals/Yamaha/tri-z_250_servicemanual.pdf




STARTING - At this point one option is the following, others would never do this.


1. Make sure cylinder/piston is lightly lubricated.

2. replace plug

3. turn off gas

4. drain carb

5. spray a short burst of flammable brake cleaner [not carb cleaner not WD40] or starting fluid down the carb throat with throttle wide open. The cam must say flammable.

6. hold throttle open 1/4 and try to start. If it does nothing try 1 more time only.


If it fires than either your plug was bad or your engine is flooding due to either a stick float, debris in needle and seat or bad diaphragm in accelerator pump.

[barnett468]

Hello


Spelling correction, cam should be can, stick should be stuck.

I have no edit button.

[El Camexican]

or bad diaphragm in accelerator pump.

Where would this be found on a stock Tri-Z?

[barnett468]

Where would this be found on a stock Tri-Z?

Right between the flux capacitor and the muffler bearing.

Post correction "accelerator" should be "fuel".

Thanks for pointing out the error however I was aware of it but I do not have an edit button and did not want to make another post correction because the moderators call it over posting even though it's not my fault I do not have an edit button, lol. Plus I was giving the OP credit for being intelligent enough to figure out I meant.

Any other errors?


Thanks again.

[El Camexican]

How can you not have an edit button? Doesn't everyone?

While we're here, I noticed you specificaly excluded WD-40, why?

[tommerp]

Edit Button?


172012

[barnett468]

How can you not have an edit button? Doesn't everyone?

Everyone except for me it seems so you can see the potential difficulties it presents.




While we're here, I noticed you specificaly excluded WD-40, why?

It's just a suggestion, that's all. Flammable brake cleaner and starting fluid are far more volatile/combustible than most other products that are easy to come by. If one wants to give an engine the best possible chance to run doing this type of test it seems to me it is best to use the most flammable product within reason. Others opinions may vary.

[barnett468]

Edit Button?


172012

Hello tommerp


Thanks for the help however I am aware of where it is suppose to be. It simply does not exist. Been over this with many other members before.

Thanks again for the effort.

[El Camexican]

Everyone except for me it seems so you can see the potential difficulties it presents.





It's just a suggestion, that's all. Flammable brake cleaner and starting fluid are far more volatile/combustible than most other products that are easy to come by. If one wants to give an engine the best possible chance to run doing this type of test it seems to me it is best to use the most flammable product within reason. Others opinions may vary.


I've always found WD-40 to light up very well and it has lubricating properties as well. I'd hate to spray a bunch of brake cleaner into my engine and have all the oil stripped off the cylinder especially if it didn't fire and was left for a week or more.

[barnett468]

Hello




I've always found WD-40 to light up very well


It's just a suggestion, that's all. Flammable brake cleaner and starting fluid are far more volatile/combustible than most other products that are easy to come by. If one wants to give an engine the best possible chance to run doing this type of test it seems to me it is best to use the most flammable product within reason. Others opinions may vary.


Below is an excerpt from Wiki, see link below for full article.

WD-40's formula is a trade secret. The product is not patented to avoid completely disclosing its ingredients.[3][6] WD-40's main ingredients, according to U.S. Material Safety Data Sheet information, are:

• 25% liquefied petroleum gas (presumably as a propellant; carbon dioxide is now used instead to reduce WD-40's considerable flammability)
• 10-% inert ingredients

http://en.wikipedia.org/wiki/WD-40


Go ahead and spray a small amount of WD40 in a small glass and flammable Brake Cleaner or Starting Fluid in another and lite them both after 10 seconds and tell me which one win’s. Watch your face!

It WAS the propellant in the WD40 that made it so flammable before and even with the old formula it was not as flammable as Brake Cleaner at least after 10 seconds and never as flammable as Starting Fluid under ANY condition.







it has lubricating properties as well. I'd hate to spray a bunch of brake cleaner into my engine and have all the oil stripped off the cylinder especially if it didn't fire and was left for a week or more.


STARTING - At this point one option is the following, others would never do this.

1. Make sure cylinder/piston is lightly lubricated.

6. hold throttle open 1/4 and try to start. If it does nothing try 1 more time only.


Below is an excerpt from Harry Klemm’s article on proper piston/ring break in. See full article at link below for more info.


About “Dry Top End Assembly” - One step that helps reduce break-in times is to assemble the top end with no oil at all on the piston skirt or cylinder walls. This step has a history worth telling.

In the middle 1960s and early 1970s American muscle-cars were a very popular item on automotive showroom floors. At that time, it was standard procedure for Detroit manufactures to assemble all automotive engines with a generous helping of oil on the cylinder bores and pistons. When these muscle-cars were first fired up, the assembly oil on the bores would burn onto the bores as a glaze that took a very long time for the rings to wear through before sealing.

Unfortunately, this assembly process caused problems for salesmen in the showroom. When prospective buyers took a muscle-car out for a test drive, it was a given that there would be at least one full throttle blast involved. During that full throttle blast, the poorly sealing rings allowed considerable oil to pass, and the brand new muscle-car would leave a big plume of unattractive blue oil smoke that could be seen in the rear view mirror…. Buyers were understandably put off by anything that appeared to be “already burning oil”.

This was a very real problem that Detroit had to address. In time, they learned that if they assembled the top ends dry, with no oil on the bores or pistons, they could avoid this initial burned on cylinder glaze. The result was much shorter ring sealing times (because the rings didn’t have to wear through that glaze), and the absence of blue smoke from those important test drive blasts.

This same rule applies to two-strokes … vintage or not. Some owners shy away from this assembly process because they fear scoring the piston … but it is an unfounded fear. On such assemblies, we do apply assembly oil to all the lower end bearings. In the first moments of initial combustion, that lower end assembly-oil disperses on the bore in even quantities that are easily enough to avert any kind of scoring. In addition, it bears noting that the lubrication needs of an unloaded engine spinning at very low rpms are very minimal. We have been assembling high performance two-strokes in this way since the early 1970’s. It works … and it results in greatly reduced ring sealing / break-in times.

http://klemmvintage.com/breakin.htm


Even though Harry does apply a small amount of oil to the bottom end bearings in the case above I believe he also mentions elsewhere [possibly in his oil migration article] that an engine is sufficiently lubricated as soon as the gas/oil mix enters it.

The reason I mentioned only two attempts with the brake cleaner is to prevent removing enough oil film from the engine to potentially cause damage.

If one is concerned about their engine being “dry” after using brake cleaner to start it. They can simply turn the gas back on, pull the plug wire and kick it over a few times with the throttle partially open.

I suggest if one cares to argue the point then one can take it up with Harry, the other option is if one is afraid of damaging their engine in any way, shape or form from this process as El Camexican clearly is that they simply don’t do it.



It's just a suggestion, that's all.

[zzmegad]

it seems like you have enough compression to fire, I think mosh is on to something, seems like it has to be your spark if the fuel is there

barnett,,, if you don't have an edit button update internet explorer, or download firefox and/or chrome. Sounds to me like an old web browser issue. Whenever I have a issue I try another browser, almost always the problem.

[barnett468]

barnett,,, if you don't have an edit button update internet explorer, or download firefox and/or chrome. Sounds to me like an old web browser issue. Whenever I have a issue I try another browser, almost always the problem.


Hello zzmegad


Thank you for trying to help me with issue.

[wisconsinite]

Hello nstyle73



PISTON/CYLINDER CLEARANCE – Should be .0024”-.0026” per manual. Since you do not have a measuring device you can estimate the clearance by doing the following.

1. Tear a piece 3” X 1/2” from std issue lined school paper.

2. Install 1” of it into the bottom of the cylinder on either the intake or exhaust side.

3. Install CLEAN DRY piston into bottom of cylinder making sure the arrow on top of it is facing forward.

4. Stop when bottom of skirt is flush with bottom of cyl.

5. Try to remove paper, if it tears it is too tight, if it pulls out with very minor effort is correct, if it pulls out easily it is possibly slightly loose in which case proceed to next step.

6. Fold paper in half, install open ends 1” into cylinder.

7. Install piston until bottom of skirt is flush.

8. Try to push piston past paper, if it does not push past paper with moderate effort it is not excessively loose, if it pushes easily it is way too loose.



RING END GAP - Your ring end gap should be .014”-.020” max per manual. See OEM manual at link below.



COMPRESSION - Should be around 160 plus or minus 10 psi, check manual to reconfirm. It might be a little low until rings seat. Compression gauges vary in accuracy.



OEM MANUAL CLEARANCES PG l3-15

http://www.oscarmayer.net/atc/manuals/Yamaha/tri-z_250_servicemanual.pdf




STARTING - At this point one option is the following, others would never do this.


1. Make sure cylinder/piston is lightly lubricated.

2. replace plug

3. turn off gas

4. drain carb

5. spray a short burst of flammable brake cleaner [not carb cleaner not WD40] or starting fluid down the carb throat with throttle wide open. The cam must say flammable.

6. hold throttle open 1/4 and try to start. If it does nothing try 1 more time only.


If it fires than either your plug was bad or your engine is flooding due to either a stick float, debris in needle and seat or bad diaphragm in accelerator pump.

Careful with the clearance and ring end gap specs here. These are the factory specs, correct? If so, i'm pretty sure the wiseco piston requires a different piston clearance.

[barnett468]

Hello Wusconsonite




These are the factory specs, correct?


Yes.






i'm pretty sure the wiseco piston requires a different piston clearance.


Excellent point to consider!


WISECO PISTON CLEARANCE PER WISECO INSTRUCTION SHEET

Normal use under 60 mm bore .002"

Racing use under 60 mm bore .003"

Normal use 60 mm - 64 mm bore .0025"

Racing use 60 mm – 64 mm bore .0035"



Below is an article from Harry Klemm regarding Wiseco piston break procedure and clearances. See article in the link below.

About Wiseco Piston Break-in - There are an abundance of two stroke enthusiasts that speak with very little enthusiasm about Wiseco pistons. The common response is “you have to give them lots of clearance … otherwise they seize”. We couldn’t disagree more … and here is why.
In the 1970s, we made many attempts to use Wiseco pistons in two-stroke race motors…with very poor results. The truth is that Wiseco (at that time) had numerous materials and design issues that needed resolving. However, Wiseco has done a great job of evolving their materials and designs since the 70’s, and today’s Wiseco Pistons are an excellent choice for most high-performance two-stroke platforms. All that said, Wiseco pistons do have one design issue that they have intentionally have not tried to resolve … longer than average piston-ring break-in times.
The forged material that Wiseco uses for their forged pistons does require “a little” more clearance and a little longer break-in that typical “cast” type pistons … but that is not the unresolved design issue…. It’s the rings. The piston ring material that Wiseco uses is a very tough material that takes much longer than average to “seal” to the bores. While the Wiseco pistons themselves are not a particularly close clearance fit to the bores, the Wiseco rings are. In truth, the Wiseco rings are made brand new with an end-gap that is much too small for full temperature high rpm operation. However if a Wiseco equipped engine gets the slightly longer than average break-in period it deserves, the outer-skin will wear off the rings to result in an ideal “running” end-gap that will give excellent long term wear and service. If however, you try to run Wiseco piston rings prematurely hard, those rings will quickly expand until the ring ends make contact and literally “bite” the full bore diameter in the ring path. Some engine builders incorrectly give Wiseco pistons excessive piston clearance in an effort to resolve this ring end-gap issue.
We respectfully submit that Wiseco pistons can be fit with very close clearances, and offer great service … as long as you let the rings have their break-in time. Our 8500rpm Kawasaki Bighorn road race bikes are equipped with 82mm Wiseco pistons fit at .0035” clearance. These pistons never showed the slightest sign of piston scoring, even after 25+ hours of racing, dyno-passes and high speed testing. You cannot abuse a piston harder than we abused these…. But we did give the rings a long gentle break-in.


http://klemmvintage.com/breakin.htm


Thanks for being polite and courteous in your comments.

[barnett468]

Hello


Spelling correction, Wusconsonite should be Wisconsonite.

I have no edit button.

[samuraiguys]

I rebuilt mine and it would not start at all, I kicked and kicked.I let it sit for a few days and fired right up. I guess I flooded the thing out bad, but weird this was is that the plug wasnt wet at all when i checked it. When it did fire boy did it blow smoke and ran rough as hell for a minute or 2. I would also check to make sure the hose running from lower jug to fuel pump isnt plugged. Should feel it pulse when kicked over.

[nstyle73]

Those crazy Tri Z's and their crazy fuel pumps. I'm simply posting to wrap up a thread for future reference for some one to use. I hate threads that are about the exact problem I have but were never resolved. I checked piston clearance and the flywheel key before reassembling the top end. I primed the pump as El Camexican suggested and it fired first kick, so I suppose he gets the win, and a thank you. I put the first heat cycle on it tonight.

[barnett468]

Hello nstyle



You can also find a lot of answers quickly by using the search engine. atc007 came up with the pressurizing suggestion at least as early as 10-26-2011 as evidenced in El Camexicans thread regarding a "no fuel" issue. It appears El Camexican had rebuilt his pump so the fact that several kicks did not get enough fuel to the fuel bowl suggests that even though according to you, your pump was working properly and therefore did not need to be primed there may some conditions under which the pump may not function well and is not matched well to the engine and another pump might work better for this particular application. See a variety of pumps at the link below if you're interested in trying a different one. Prices start at $18.00.

http://www.ebay.com/bhp/mikuni-fuel-pump






I put the bike together and it fired once and I have not been able to get it to start. The bike ran fine before teardown. I have spark, and swapped plugs to check. I also believe that the fuel pump is working as there is some fuel in the cylinder when looking in with the pipe removed. I also checked fuel flow out of the pump by kicking it over.

It made no sense to prime your pump based on the fact that you said you had the following:

1. Fuel in the cylinder.

2. Changed spark plugs.

3. Your fuel pump was clearly pumping fuel because you checked it.


These things point more towards a flooded cylinder, not an engine that had no fuel. It might have been flooded and simply sat long enough for the excess fuel to evaporate.





Originally posted by El Camexican on 10-26-2011, see thread in link below for more info.


For some reason when I run out my primary Tri-Z fuel and switch it over to reserve I can't get it to restart unless I manualy prime the engine with fuel. The pump is rebuilt and works fine and the engine is tight.


PITA,,but ,Blow in the tank vent line,,heck it's right there at the handlebars,,you don't even have to get off and remove the seat. This pressurizes the tank and primes the pump right up to the carb. Only takes a cpl seconds. She'll start 1st kick : )


I'm going to try atc007's advice and "Blow"!


http://www.3wheelerworld.com/showthread.php/136816-Priming-Tri-Z-fuel-pump

[barnett468]

Hello nystyle



Any help on the ring end gap or other suggestion would be appreciated. Its disappointing because the base gasket leak wasn't that bad.

I posted the stock ring end gap earlier if you need that.


Wiseco ring end gap for your app = .004” per 1 inch of bore diameter for top ring and .005” for second ring. Your bore is 2.75” so do the following:

TOP RING - Multiply .004” X 2.75” = .011” end gap.

SECOND RING - Multiply .005” X 2.75 = .01375”, round up to .014” end gap.

DOWEL PIN RING END GAP – If your piston has dowel pins to locate the pins the gap here should be .010” greater than the diameter of the pin.


http://www.wiseco.com/PDFs/Manuals/RingEndGap.pdf

[nstyle73]

um...thanks.

[El Camexican]

Glad to hear she fired up! Hope you have a blast riding it! :beer

[zzmegad]

I also have used that trick, and it works great when the carb is empty. Of course when it is full you can't blow because the float valve is sealed, but there should not be issue starting if the carb is full anyways right? For some reason, if my Z has sat for more than a few days it always takes 10-12 kicks to fire, I just don't get that. She always fires on the 10th or 12th, and my carb is always full I think, I mean it doesn't leak, and if I blow its pressurized and blows back at me,,, weird

[El Camexican]

I also have used that trick, and it works great when the carb is empty. Of course when it is full you can't blow because the float valve is sealed, but there should not be issue starting if the carb is full anyways right? For some reason, if my Z has sat for more than a few days it always takes 10-12 kicks to fire, I just don't get that. She always fires on the 10th or 12th, and my carb is always full I think, I mean it doesn't leak, and if I blow its pressurized and blows back at me,,, weird

Try doing the blow thing if it has sat over night and it should fire on the first or second kick, mine does. I guess fuel evaporates out the vent tubes when they sit whereas a gravity fed carb would fill as soon as you turned the fuel on.