Type A Type B

[crassius]

if you find no marks on top or skirt of piston, check to see if compression seems higher than normal

if the stroke is 40mm, then usually an extra gasket is used at cylinder base, but as a test, you could try a 2nd head gasket

 

[INTP_ty]

Bumping this thread. Bike is nowhere near as fast as my last one. Somethings wrong. Tried 2nd gasket. Notta.

Are the rings universal cuz I ordered some on EBay. I broke my originals trying to seat it. Maybe I have the wrong rings on there????

 

[FurryOnTheInside]

I want to see this broken transfer port.

The rings for the 66/69/"80"cc engines are all the same, AFAIK.

 

[crassius]

with no compression test, it could be many things - old cylinder too worn for new rings to seat well, gouged cylinder from when rings broke - old cylinder had diff port mapping from the original

 

[INTP_ty]

The roller bearings for the wrist pin are standard, the same for both A and B pistons.

This photo begs to differ. I swapped out the smaller roller with the wider one. I’m gonna go see if this eliminates that noise....

The piston is scored btw. It looks like I got a bad cast from the factory.

Oh I attached a photo of my chipped jug. It’s junk now though -scored up.

 

[Street Ryderz]

This photo begs to differ. I swapped out the smaller roller with the wider one. I’m gonna go see if this eliminates that noise....

The piston is scored btw. It looks like I got a bad cast from the factory.

Both are used in our engines the long one you used is the preferred one to reduce walk and keep the rollers positioned in the rod better.

 

[INTP_ty]

Both are used in our engines the long one you used is the preferred one to reduce walk and keep the rollers positioned in the rod better.

Here

 

[Street Ryderz]

Here

Time for a new top end and flush or open the bottom as well to make sure there are no remnants left behind.

 

[crassius]

there are threads here from years ago about spacing those short bearings, but I'd rather just use longer ones