Scooterotica

Great little kit but I've just popped the second piston due to the rings breaking up and pinking out through the exhaust. What causes them to break up? I might get another kit or get another rebore.

Running through a 20mm Dellorto and SIL Clubman. Carb main jet was slightly weak but the plug was still brownish.

I use semi synthetic at about 25/33 -1.

On points.

Ports too large causing the rings to snag and break?

Exhaust port to wide. Ditch it and get another you'll never stop it happening otherwise.

A pal repeatedly broke rings because of his exhaust port being too wide. He did something like 6 pistons before finally admitting defeat and getting a different barrel.

Who ported it? Go back to them and get them to stand the cost of a new barrel.

So I've stripped it down. As I thought, half the bottom ring went out through the exhaust port. You can see where the ring caught the top of the part of the exhaust port. It's a standard AF 175 kit. I'll take it in and see what they say. Maybe a thicker base gasket might work but I'll probably get another kit, more damn money.

ring gap on assembly

He checked the ring gap in front of me last time. It's a shame as the kits can go well.

it not that easy to see from the pic, port doesnt appear overlarge, maybe some more pics, is the edge of the port chamfered ?