Engine Trouble 50cc newer engine tuning problem

[wan37]

40mm stroke on the af80?

I searched it and it said high hole piston long rod . It didn't say the stroke size

 

[Karl Snarl]

I searched it and it said high hole piston long rod . It didn't say the stroke size

Thank you, brother.

 

[Karl Snarl]

AF 80 rod
The 48cc is only one piston and 38mm crank, the Af80 rod is for high hole regardless of stroke though I believe most are 38mm stroke.

Thank you for the info, makes me a little sad though. I wanted a 40mm stroke. lol. Still it's a nice engine for the money I paid.

 

[wan37]

This thread was about a 48cc as there really isn't a 50cc and there piston is only one type with 40mm dia.

I was the op of this thread but I learned some good info on break in . Always a pleasure of learning.

 

[Aikaru]

This thread was about a 48cc as there really isn't a 50cc and there piston is only one type with 40mm dia.

After taking the piston off, I found that because the rings didn't set properly (also the rings look crappy as can be from factory) the skirt of the piston has a big scratch on each side where the transfer ports are. It looks like the rings were too small and the piston was actually wider than the rings lol. I checked the cylinder body though, it doesn't need to be replaced. Some very very small scores, but nothing actually visibly noticeable and it's smooth all over on the inside.

 

[Greg58]

The title of this thread said 50cc, all along I thought you had the small engine. While yo u have the piston out measure to the top of the piston pin, 15/16?is type A , 1-1/16 is type B. Just order the piston type you need, its best to replace the complete top end at once, especially if you have damage to either part.

 

[Aikaru]

The title of this thread said 50cc, all along I thought you had the small engine. While yo u have the piston out measure to the top of the piston pin, 15/16?is type A , 1-1/16 is type B. Just order the piston type you need, its best to replace the complete top end at once, especially if you have damage to either part.

Okay, I will order a new cylinder body too then...

 

[Greg58]

The problem using a used cylinder is it may take some extra time to seat the rings, that’s why you hone a cylinder when you rebuild a engine, even if you only replace the rings. With the super thin coating in these little engines honing may damage the bore.

 

[Greg58]

Sorry Wan37, somehow we got off of your problem and on to Aikaru’s.

 

[Aikaru]

The problem using a used cylinder is it may take some extra time to seat the rings, that’s why you hone a cylinder when you rebuild a engine, even if you only replace the rings. With the super thin coating in these little engines honing may damage the bore.

i assume i dont need to do all that if i just buy a new cylinder?