Why would it smoke?

[paintslinga2010]

I bought a warrior for cheap from a guy who said he stopped riding it because it was smoking so bad. It had been sitting for a while so i didnt bother to try to get it started. I assumed I would tear into the motor and find a stock piston and obvious signs of needing a rebuild since it is a 92. What I found doesnt make much sense to me. First I pull the head and the combustion chamber is surprisingly clean. I look at the piston and it looks to be an oversize since it has a 50 stamped on it. Would that mean its .5mm=.020? I turn the motor over to get a look at the cylinder wall and I can still see cross hatch on it. What the heck? The only issue I could find is a broken exhaust stud. Maybe he ran it with the broken stud and it leaked burning up rings? I am at a loss. I will attach some pictures.

 

[94warpig]

Valve seals?

 

[beastlywarrior228]

Just because the cylinder is still good doesn't mean the rings are, that happened to me last summer with my JE

 

[paintslinga2010]

Is there a way to tell if the rings are bad by looking at them?

 

[beastlywarrior228]

Not really youll need to take a ring gap measurement and find the tolerance between the rings and cylinder

 

[paintslinga2010]

Well lets say the rings are bad. I can still see the cross hatch on the cylinder. Would new rings seat?

 

[bones]

not properly ... just a quick hone and new rings should fix the smoking ... oh and valve seal if there bad

 

[paintslinga2010]

Would a regular 3 stone hone be sufficient or do I need to use a flex hone?

 

[lbjamm]

3 stone is fine. That's what I use.

 

[redrum]

mine smoked like a pig..valve seals..and a little adjusting

 

[lbjamm]

mine smoked like a pig..valve seals..and a little adjusting

Pigs smoke?

 

[WarriorNewbie]

Yum! Smoked pig!

 

[redrum]

nothing is better than a smoked pig..

 

[Gen1Pat]

I prefer flex hones. I've seen the 3 stone centrifugal damage a cylinder if you are not carefull. That is a .020" over Yamaha cast piston. If there is no ridging at the top of the cylinder, and there is healthy cross hatch remaining, hone it & install a Wiseco or JE forged piston. Get a little more power, and have a MUCH better piston.

 

[WV98YFM350]

Wiseco, bc JE smallest size is 85.00 mm big bore

 

[paintslinga2010]

Im going to hone it and put new rings on the yamaha piston. I bought it cheap si I will keep it cheap and work on the chassy. Ive got another motor that has a chewed up head I plan to build up later. Thanks again everyone. Love this forum.