Chinese 80cc Engine kit.......

Discussion in '2-Stroke Engines' started by dave#22, Nov 4, 2014.

  1. dave#22

    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 :rolleyes7:
    Should be fun.
    Last edited by a moderator: Dec 18, 2015

  2. crassius

    crassius Well-Known Member

    sounds a bit like the kits we used to get about 4 years ago (had similar problems at times)

    I'm curious as to whether the crank has metal rings bolted to the outside, or is machined to appear as one piece as the newer ones are.

    as to suggestions, I'd say you have this well in hand
  3. dave#22

    dave#22 New Member

    The crank halves are one piece, not bolted up.
    The strange thing is, is that there is no manufacturers name on the engine, documentation or box that it came in, just....80cc MADE IN CHINA.
    The original bearings appeared to be of good quality, but I changed them to be sure.
  4. crassius

    crassius Well-Known Member

    not at all strange with these - several places make the parts & folks that sell kits buy whichever is cheapest this week - slight discrepancies in fit & finish are common - they are so simple though, that all seem to run in the end