dave#22
New Member
Hi All, After some consideration I bought a Chinese 80cc (actual 66cc) engine kit, here in England. I read up on this forum for potential problems, the main one being the piston being fitted back to front.
So when the kit arrived, I took the head off the engine and the arrow on the piston was pointing toward the inlet, the second was that the engine was very tight to turn over, so I contacted the supplier for a refund and eventually agreed to a refund minus £15 and keep the kit.
I stripped the engine and found that the crank was tight between the main bearings, as the RH bearing housing had not been machined deep enough, and the LH main was a 2RS, so I ordered 4xSKF (ZZ mains with the inner shields removed) bearings, a new RH oil seal and a new little end bearing.
After some work, the crank rotates freely, so I matched the transfer ports with the barrel, but found the exhaust port and transfer ports low to the piston on BDC....and reading here that the compression ratio was too high....made a 1.5mm shim to fit between the barrel and crankcase, which raised the ports to the piston.....the piston skirt partially obscured the inlet into the crankase, so that was cut away to clear. The ports in the barrel were quite poorly finished, so I spent some time on them to improve the flow, lapped the head and barrel faces and put it back together today.
Any suggestions before I proceed?
I intend to fit the kit into a Dutch ladies framed bicycle
Should be fun.
Dave.
So when the kit arrived, I took the head off the engine and the arrow on the piston was pointing toward the inlet, the second was that the engine was very tight to turn over, so I contacted the supplier for a refund and eventually agreed to a refund minus £15 and keep the kit.
I stripped the engine and found that the crank was tight between the main bearings, as the RH bearing housing had not been machined deep enough, and the LH main was a 2RS, so I ordered 4xSKF (ZZ mains with the inner shields removed) bearings, a new RH oil seal and a new little end bearing.
After some work, the crank rotates freely, so I matched the transfer ports with the barrel, but found the exhaust port and transfer ports low to the piston on BDC....and reading here that the compression ratio was too high....made a 1.5mm shim to fit between the barrel and crankcase, which raised the ports to the piston.....the piston skirt partially obscured the inlet into the crankase, so that was cut away to clear. The ports in the barrel were quite poorly finished, so I spent some time on them to improve the flow, lapped the head and barrel faces and put it back together today.
Any suggestions before I proceed?
I intend to fit the kit into a Dutch ladies framed bicycle
Should be fun.
Dave.
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