Damn TRX250R motor issues! Help wanted

[lisnup65]

For those who remember, I picked up a Fairly clean 86 250R back a few months ago. Well come to find out the motor cases were cracked so I plucked the motor and welded them up. After replacing bearing after bearing its all back together. I did not change the rod or the piston as it only had around 4 hours or so on the top end. The piston and rings looked like new and I had no play out of the upper or lower rod bearings. I replaced the rings anyways as I was in it and also the circlips.

Now, on to the problem. The machine started first kick which even shocked me, but I noticed that I have a bit of piston slap. You know the ticking sort of sound. I was amazed that its there as I did not have it previously or not that I can recall. My 85 250R is extremely quiet next to this one. I am not 100% sure its piston slap as I have a ATC head gasket on this TRX for added compression. I am not sure yet if its just detonation that I am hereing from low or to low of an octane. I beleive I have preminum, but I could be mistaken. I will get fresh fuel this week. I also have not compression tested as I was trying to seat the rings first.

Should I rip back into her, or ride it out a bit?

Thanks,
Dave

[x.system]

Did you make sure your piston would clear the head gasket? Check your squish clearance?

[wheelie king]

Take this for what it's worth, but I'd try some high octane/race fuel gas in there and ride it a bit. I'd have to listen to it......you sure it's not "pinging"?????

[OldSchoolin86]

Did you make sure your piston would clear the head gasket? Check your squish clearance?This is what I was I thinking, maybe it's hitting.

[lisnup65]

I dont think its hitting, but I could remove the head to check it over again. This machine had the Paper style gasket on it and thats why I went with it again. It was .050 thinner than the metal gasket. If I remember it was .090 for the Metal TRX spec and .040 for the Paper ATC spec.

Also if it was hitting, I would assume that with more rpm's the more it would be. It actually quiets up a little.

[MTS]

well its quite easy to check your squish to see if it is too small really, just take a piece of sodder and make a right angle with it so you can stick it in the spark plug hole and get it over to the very edge of the cylinder, then just kick it over once and then pull it out, measure it with a venier caliper and whala there ya go, should be good if your around .75-1 mm

[OldSchoolin86]

I dont think its hitting, but I could remove the head to check it over again. This machine had the Paper style gasket on it and thats why I went with it again. It was .050 thinner than the metal gasket. If I remember it was .090 for the Metal TRX spec and .040 for the Paper ATC spec.

Also if it was hitting, I would assume that with more rpm's the more it would be. It actually quiets up a little.
I had an LT250 that hit and it didn't get louder the more you rev'd up. You'd think it would, I agree. IDK, it's long shot advice but you never know.

[lisnup65]

I took a cold compression test which I know will not give the full compression, just wanted a cold guide. I have 180 cold! Once I get fuel later this eve, I will warm the motor and recheck.

I put a piece of .050 solder down in the cylinder, moved the piston through a rotation and rechecked. The solder mic'd out at .040 to .045 which is greater than the 1mm reference.

[hrc85250r]

my R has 215 and i ran it on pump and i didnt hear any knocking or anything, just my counterbalncer....i run cam2 now just to be safe and i have a brand new counterbalncer straight form honda waiting to go in, i am going to get a hinson adjustable counterbalncer bearing holder before i put it in....

[lisnup65]

Well after a quick 3/5 minute warm up, I hit 187 with my Snap-On compression tester. So only a 7psi pickup when warm.

Anyways, I really am against the detonation issue as if memory serves ccorrectly, detonation will be more evident while getting on it and NOT at idle.

So I guess I will pluck the top end again and check the piston to cylinder clearance and see how that looks. Does anyone know what I should see. Its a Weisco Pro lite at 1.00 over. I did not have the machine work done so I do not have the box for spec. If it is within spec then the only other thing it can be is the crank or crank bearings.
Just sucks cause I asked other to feel the bearings and give their thoughts and they were with me. No up/down play, just a little normal side to side.

[lisnup65]

my R has 215 and i ran it on pump and i didnt hear any knocking or anything, just my counterbalncer....i run cam2 now just to be safe and i have a brand new counterbalncer straight form honda waiting to go in, i am going to get a hinson adjustable counterbalncer bearing holder before i put it in....

Whats Cam2? I rebuilt the counterbalancer so I know the bearings on it are A OK.

[x.system]

Cam2 is 112 octane, race fuel.

[lisnup65]

I guess its sorta like this, but not near as bad.

http://72.29.68.184/%7Edespera/Video%27s/250r%20motor%20sounds.wmv

This is the worse I have ever heard!!!!!

[x.system]

That sounds bad, I wouldn't even run it like that. I would pull the top end off and check everything. Who's bike is that, looks familiar.

[lisnup65]

That sounds bad, I wouldn't even run it like that. I would pull the top end off and check everything. Who's bike is that, looks familiar.


Mine is no where near that, but the sound is familuar. That is a member off R-Central named the ladies man.

I am just annoyed cause I dont remember it before hand or at least not like it is now. All I did was fix case, replace bearings, very slight hone and new rings. I wish I had pictures of when I removed the piston. You would have not know it had more than 10 minutes on it.

Oh well they joys of doing your own wrenching. Back on the table she will go.

[MTS]

I guess its sorta like this, but not near as bad.

http://72.29.68.184/%7Edespera/Video%27s/250r%20motor%20sounds.wmv

This is the worse I have ever heard!!!!!
im new to 2 strokes so gime some slack if im wrong hear, but the detonation would be that constant tick on that thing right?

[lisnup65]

im new to 2 strokes so gime some slack if im wrong hear, but the detonation would be that constant tick on that thing right?


That is beyond detonation! Their is definite piston slap or rod slap going on in that motor. Detonation if my memoty is correct will be most prevaliant under load and NOT at idle.

[RideRed250R]

I thinks ** problem is piston slap with rod slap and why it quiets down when * add gas is it gets enough case pressure to keep it off ***** from rocking as bad, I says rip it down and do it again, if * runnin it more the sound will get louder and the bottom end might be freid, I also suggest getting a new rod also as this one could be slightly "grooved from being fired on and slapping around" thats the worst case problem, it also just could be piston slap from being broke in 2 times cause ** clearences from being takin apart and being put back together 2 times are different. i hope * have luck with this
adam

[TRIKE]

Dunno if this will help you or not. 86 TRX's have a higher exhaust port than there latter yrs.This is partly why so many want the motor from an 86.ANyhow,do to this higher port,if all you have done is hone the cylinder,you might be running into exhaust port slap.Mine had done this as well. What happins is as the piston wears,it starts to rock front to back,this cause the piston to just catch in the upper side of the higher exhaust port.Not a good thing. If you dont catch it soon enough you will be resleeving a good jug and possibly worse dmages if it hangs altogether. If you have to tear it down,look to see if theres any hair line cracks running off the exhaust port into the cylinder walls.You should see some flatness to the edge of the top of the port ,as well as the piston will have marks on it. HOpe this helps,hope its not the problem. Good luck.

[ChrisD]

What's up guys.

It's not detonation. You can cross that one off the list. You will know detonation when you hear it. It's a pinging noise from the cylinder when you're hard on the gas (sounds like a death rattle). 180 something in compression is not enough to cause detonation, so I wouldn't worry about that.

I've had that noise in the past:

The most common cause of that noise is piston slap. If you honed the motor, that would be my first place to start. Check your piston clearance (piston to cylinder wall clearance). Excessive rod clearance makes a knock when you're decelerating. The wear limit is .14mm or .006 inches. Normal is .06 -.08 mm or .0024-.0031 inches. (also make sure that you don't have a sticky ring)

I also had that noise come from my counterbalancer. I rebuilt my bottom end 2 years ago because my motor sounded like a time bomb. I thought it was crank bearings, but it tuned out to be a loose fit on the counterbalancer bearing. I had a new bearing pressed on it in 1997 and I guess it came loose over time.

If this means anything, you should fix that noise, but I raced my bike for 2 years like that.

Hope this helps.