[T-Dub13]

Nice work Bohon. The only thing I'd add is a small slot in the rear just below the bottom ring. This slot should match up to the top of the intake port at BDC. This won't really help performance, but it lets some fresh charge into the underside of the piston and will help keep the wrist pin and bearing happier and a little cooler. See attached pic of a 2000 KX80 piston. I've done this a lot. It won't hurt performance, so for what it's worth, might as well add it on.

 

[Bohon]

i do have one question what could i use to shim the rist pin between the rod and the piston or does it even matter.

 

[T-Dub13]

You shouldn't need a shim. The big end bearing should be tight enough to not allow play and keeps it centered. There are usually shims (thrust washers) on either side of the big end bearing in the crank assembly that limit side play. If your con rod has play from side-to-side, you need to measure it to make sure it's within spec.

 

[Bohon]

where the piston connects to the rod ?

 

[T-Dub13]

#7 is the thrust washer. As long as this and #9, the big end bearing are good, you wouldn't have any side play in the rod.

 

[bigrob981]

I appologize for bringing up a dead thread...but this is the only information I have found on using a YZ80 cylinder on a YZ60 engine....More info please?

 

[T-Dub13]

Use a 1981 YZ80 Cylinder, piston, rings, head, reeds, boot and carb. 1981 only.

PM me and I'll recieve an email so I know to reply. I'm never on here anymore. ...Racing a YZ490 and a 1979 YZ125 now.