Greetings from Estonia

Sorry for my English.
I bought my XT600 couple of years ago. I ve put around 1.8k euros into repairs and I still can't drive it.... Since ive owned it, I have around 2500km only with it and all the other time I have owned it, it was in garage or repair shop...Have done basically everything with it and it is pointless to sell it...it was somewhat in bad shape and bad buy...but it was only 650€ then...


Now heres the problems I have had...
* Could ride it around 100km, then it started backfiring - Carb. seal was busted.
* Cylinder was taken off and found that crankshaft was moving too much, too large piston inside.. - Total bottom and top rebuild. New crankshaft + bearing, piston, rings, valve stem seals etc...
****Then it all started***
*Rattle from engine....called mechanic and got it back to shop.. valve regulating etc...he said that head was busted, that it got too much movement with arm rockers..that I would need new head.
He said that it wont damage the engine and I can ride it.
* Couldn't check oil after 1000km break in period..i guess around 300km or so later when I discovered it - oil didn't stay in the oil tank at all
* Started smoking when cold around ~1800km after rebuild.
* Smoking lasted longer the more i used it.. i guess 2000km or so.
*Finally fixed oil leakdown around 2100-2300km or so... - clutch cover ball+spring+seal fixed it.
* Started smoking little when accelerated ~2300-2400 ..
* Started to smoke all the time after that and I stop riding it
* Rattle was same since beginning after the rebuild.
* Now I got the head changed with valve job + new seals...Huge dissappointment when everything was totally the same...same noise and smoke - I believe that piston rings are busted...but 2500km and stuck?

Heres a video to describe it.
Xt600 rattle and smoke - YouTube

Rattle is the same with cold or warm engine....sometimes it stops for like 5 sec...sometimes tilting the bike makes it stop rattling for few sec.
What can cause that ? Its not the nut from right side of crankshaft. Could chain tensioner make that? What caused it to smoke? Did I damage it when all the oil was in the engine since the valve didn't hold oil in the oil tank? Found that carb. was bit dirty of dust with 2000km...could some dust damage it? Cylinder was OK when i asked other workshop when they changed the head.

But yeah...what causes the noise? First mechanic told by phone that he still believes its the head...but its other head from other bike and still smokes and rattle after valve job+seals....I do not believe it.
I got 2 versions:
1. Rattle of something caused something that killed the rings( dont know what else it damaged since havent seen piston or bottom end after that.
2. Too much oil in engine- caused it to push exessive oil to top end and from there through valves to combustion chamber... And that oil caused to burn the 2500km rings stuck? That would normally explain why it smokes when cold but it doesn't make sense right now since new yamaha stem seals and valves done..
Any ideas....again sorry for my English.

:confused1::confused1:

Maybe worth checking the oil pressure at the liitle bleed screw on top of oil filter housing,Then you may want to take the top off and look at everything carefully including how the lubrication system works..I'm sure it will all become apparent.
Stick with it and I'm sure you will get there..

Hi sounds like some bad workmanship at your expense ! have you tried to locate the noise by using a length of hose , one end in one of your ears and the other near your motor, move it around to see if its at the top bottom or middle of your motor ?? you may need to put an ear plug in your other ear to block out all that rattle. It sounds bad. You need to trace that sound down before you try to fix the smoking again.

From JJ's reply in the ADV forum, it looks like the mechanic put in a standard piston in a cylinder that was bored to .25mm. Yes, that will rattle very bad. Confront the mechanic and get him to make it right.....


Good luck....

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'84 XT600 is now bored to 2nd oversize and new OEM pistons and rings installed. No more smoking.

I just listened to that finally, wow! I will reinforce my original idea that he put the standard piston in an overbored cylinder . That sound is close to what a piston skirt slapping the cylinder wall is like only I've only heard one that are from normal wear, yours is beyond excessive. That will be the cause of all the smoke , just surprized it even has enough compression to run. That piston will have broken skirts by now .

Yeah, started to think that it is most logical answer to that, cause if the piston was to big before, it should had had wear marks everywhere...but only 4 "corners" cause it got heat with previous owner. Also I think it couldn't fit in there at first place if it was too big?
I will talk to mechanic. When I called him few days ago he said that he will look into it next week.
I will keep you posted.

JJ is saying the piston is too small !! It dosnt take much clearance to cause a problem . And you wasting your time guessing it needs to be striped down and measured but listen where the rattle comes from first. It sucks but there is no other way . your mechanic should help ? good luck. not approaching him like an ass will help LOL ( I,m a mechanic ) I get to meet them all let us know where the noise is coming from.

A person may be able to get an idea if thats the issue by putting a dowel down the sparkplug hole and pushing down on the front, then back, and repeat, to see if you can feel the piston rocking and how much. If it is .01" (.25mm) undersize it will rock noticeably.
As long as it's an honest mistake no point in being aggrivated toward him. If he's got any morals he'll be pissed off at himself just for doing it much less getting ragged on extra. Just depends how it turns out as to whats going on, maybe something simple is going on.

Didn't think of it earlier but if your at .25 over , a 96mm may be all the bigger piston needed.

I won't rage, not that kind of person. But it is his fault and letting him to fix it.
Im taking engine off today and take off the head to check it out.

I visited the other shop yesterday who changed the head last time, they had mouths open after they saw the video. They also thought its bearing or piston or somewhere there.
Although they didn't see anything wrong there when they took head off and said that 0.25 can't really be seen by eye(alo they didn't know about that rattle problem, cause I thought it was head fault and will be fixed with new one..).

I will keep you posted. Thanks.

Im not a expert mechanic. But I believe that is not normal...what the ...
https://www.youtube.com/watch?v=FMoXxMQHrCI

It may be best to not have him fix it but pay another(or should I say AN actual mechanic) to fix it. With the miles it was riden (because he said it was ok too) the skirts are most likely broken and the motor will need to be checked over fully to make sure chunks haven't done any other things.

At least now you can move forward and get your bike ridable.

I agree with JJ, if this guy was this incompetent in the first place, why trust him to get it right. Hard lesson, but putting good money after bad and still wind up with problems is not the way to go.

__________________
'84 XT600 is now bored to 2nd oversize and new OEM pistons and rings installed. No more smoking.

Hi good to see you found the problem ! show us what the piston and bore look like ? Did it seize up while you were riding it with broken intake manifolds it would have been running very lean mixture and that could overheat piston , piston grow with heat and pick up on the bore wearing away at new tight piston ?

* Cylinder was taken off and found that crankshaft was moving too much, too large piston inside.

This bit makes no sense to me ? if piston too large it wouldn't make problem with bottom end ?

valve regulating etc...he said that head was busted,

not sure if it translation but I never heard of valve regulating ?

Let us know how you get on :confused1:

I haven't taken off the cylinder yet, cause I want to show that to mechanic who did that, somewhere next week. Then I can take it off. Maybe I will take it off next week, since I can put it on again...
It ran good and had no problems except very small rattle when I bought and rode it ~100-150km before repairs.

Carb. had old seals and it started to backfire and after that the engine went to repairs. He also tried to find out the small rattle.


I don't know either, how this piston was too big. But crankshaft had too much play and got heat aswell I think(as seen on piston ) with previous owner, but could ride it with no problems, just little rattle.
https://dl.dropboxusercontent.com/u/...tud/piston.jpg


I ment valves clearance check with valve regulating. He said that the rattle is from head cause rocker arms had too much movement.

I will let you know what will happen.

Look very close at the piston top and the valves to see if any have been touching. You will see a smooth bright spot on the valve if it has been touching. I say this because another owner had a worn out cylinder and the piston rocked similar to yours and his actually touched the valve and made the same noise as a loose rocker arm to valve stem clearance. His required boring to the next size and fitting a new oversize piston.

I also suggest that if your guy is savvy enough, have him check the cylinder bore for out of round or oval shape. There are spec's in the manual for that and if it is out of tolerance, bore and fit (carefully) a new piston. Since you are at .25, the next logical over bore is .50. In the USA yamaha pistons do not come in the .25 size, the first overbore size is .50. Not sure where you live what is available. Other yamaha models start at .25 for first over bore, but not the XT600.

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'84 XT600 is now bored to 2nd oversize and new OEM pistons and rings installed. No more smoking.