More power question

Discussion in 'General Questions' started by JVROOM, Sep 4, 2012.


    JVROOM Member

    66 cc slant head, anyone ever messed around with changing the head or milling it down to increase the compression for more power? Might be fun, or is it worth it. Or as a say if it anit broke to mess with it?

  2. motorjake

    motorjake New Member

    ive recently had to do a full top end rebuild and i changed from the slant to standard head, i dont really see a difference in power, just the spark plug now sits straight insted of being on an angle lol.
  3. Fabian

    Fabian Well-Known Member

    The slant head will give you more compression than a conventional low compression cylinder head due to it's more compact packaging (enabling it to fit into space restricted bicycle frames), though i have purchased a replacement engine fitted with a high compression cylinder head and centrally located spark plug.
    These were received by the wholesaler in Melbourne (Australia) but only in one of their shipping containers; the other shipping containers had engines with the conventional low compression cylinder heads.
    Surprisingly the engines fitted with high compression heads were superbly designed, and the combustion chamber was a virtually identical to that of the Rock Solid Engines high compression cylinder head, yet it looked exactly like a standard Chinese cylinder head on the outside. The only downside was that the high comp heads caused engines to detonate so badly (with the standard Chinese CDI) that just about every engine came back as a warranty job due to a failed big end connecting rod bearing.
    My high comp engine suffered the same fate, lasting only 15 miles before the big end failed.

    Thankfully the Jaguar CDI fixes the problem of the incorrect ignition advance curve of the standard Chinese CDI; being able to safely use a high compression cylinder head without the engine detonating itself to bits, due to the multi-adjustable ignition curves.
  4. jaguar

    jaguar Well-Known Member

    Just mill .5mm off the standard head to get the needed compression. Change the wrist pin bearing also since the stock one is junk.