toojung2die
Active Member
Everything has been going great with the new motor bike. Every road is a hill around here but there's only one that needs some pedal assist to climb. The engine is on it's second gallon of fuel, still breaking it in. One day out the blue it wouldn't climb that steep hill at all. I checked compression and it's only 60 psi. I don't know what the compression used to be but I know 60 psi ain't good.
Head is torqued to 12 ft/lbs, I check it often. No oil leaking out around the head or jug. So I take off the head, no problems there and the gasket looks good. Next I take off the jug. The cylinder walls look good with some cross hatching still showing. When I inspect the piston and rings the problem is evident.
The top ring locator pin was pushed all the way in and isn't doing its job. The top ring spun so the gap lined up with the exhaust port. The ring is shot and the piston is useless without the locator pin.
I replaced the piston, rings and wrist pin. Assembled it all with new gaskets. The engine started right up and runs great. After a couple of easy 15 minute rides and cool down I tried the hill. The power is back like before the problem. I'll do another compression check after I think the rings have had time to seat.
This engine has a type B, high hole piston. eBay has lots of type A piston kits that include the rings, wrist pin and G clips. Why don't they sell similar kits for type B? I had to buy everything "a la carte". Even so, you have to admit parts for these engines are ridiculously cheap.
Jon
Head is torqued to 12 ft/lbs, I check it often. No oil leaking out around the head or jug. So I take off the head, no problems there and the gasket looks good. Next I take off the jug. The cylinder walls look good with some cross hatching still showing. When I inspect the piston and rings the problem is evident.
The top ring locator pin was pushed all the way in and isn't doing its job. The top ring spun so the gap lined up with the exhaust port. The ring is shot and the piston is useless without the locator pin.
I replaced the piston, rings and wrist pin. Assembled it all with new gaskets. The engine started right up and runs great. After a couple of easy 15 minute rides and cool down I tried the hill. The power is back like before the problem. I'll do another compression check after I think the rings have had time to seat.
This engine has a type B, high hole piston. eBay has lots of type A piston kits that include the rings, wrist pin and G clips. Why don't they sell similar kits for type B? I had to buy everything "a la carte". Even so, you have to admit parts for these engines are ridiculously cheap.
Jon