What kind of piston is this?

[junglerunna]

What kind of piston is this? I think its a Wiseco. I can get the numbers off the top if needed.

[junglerunna]

another view

[junglerunna]

pic

[wilkin250r]

Numbers off the top would be extremely helpful.

[Crazy lil punk]

looks like a used one to me :) , lol, I had to do it, free bump

[C-LEIGH RACING]

Wiseco prolite 87/88/89 model R engines & those rings are way past time to have been replaced. The dark color on the side is from blow by when the spark plug fires & rings cant hold the explosion presure, or compression.
Neil

[junglerunna]

The numbers on top of the piston are:

7376K
562M06750


Originally posted by C-LEIGH RACING
Wiseco prolite 87/88/89 model R engines & those rings are way past time to have been replaced. The dark color on the side is from blow by when the spark plug fires & rings cant hold the explosion presure, or compression.
Neil

This piston and rings I believe have about 15 or so hours.

What should I replace the piston and rings with?

[C-LEIGH RACING]

Originally posted by junglerunna
The numbers on top of the piston are:

7376K
562M06750



This piston and rings I believe have about 15 or so hours.

What should I replace the piston and rings with?


That is a 67.50mm size piston you are showing. You only have one more size, a 68.00mm that you can go to in that style of piston for the late model cylinder.
You can however if you want to do the spacer plate mod & use the old 85/86 model piston.
This piston is made different from the 87/88/89 models & you will need a spacer plate to fit under the cylinder base for it to work. The old model piston will allow you to bore in up to a 69.50mm size in the late model cylinders.
You can as well after the 69.50 size is worn out use the piston from a 86 YZ250 Yamaha in the 70.00mm size, but you would still need the use of the spacer plate.
Neil

[Eddiesanders250]

whats the max bore on a stock cyl? is it 70mm

[junglerunna]

Originally posted by C-LEIGH RACING
That is a 67.50mm size piston you are showing. You only have one more size, a 68.00mm that you can go to in that style of piston for the late model cylinder.
You can however if you want to do the spacer plate mod & use the old 85/86 model piston.
This piston is made different from the 87/88/89 models & you will need a spacer plate to fit under the cylinder base for it to work. The old model piston will allow you to bore in up to a 69.50mm size in the late model cylinders.
You can as well after the 69.50 size is worn out use the piston from a 86 YZ250 Yamaha in the 70.00mm size, but you would still need the use of the spacer plate.
Neil

Thanks for the reply. What you saying is that I can put a 68mm of the same style piston in my cylinder the way it is now? Since I have the cases split I noticed I have a late model hot rod crank in there. How much side to side play is the connecting rod allowed to have with that crank? Same as oem spec?

[C-LEIGH RACING]

Originally posted by Eddiesanders250
whats the max bore on a stock cyl? is it 70mm

Safely the 70.00mm size should be the last, but I've heard of a 71.95mm being used before, cylinder sleeve is mighty thin though.
Neil