Motor bottom end, have I done this backwards?

Discussion in '2-Stroke Engines' started by JVROOM, Oct 11, 2012.


    JVROOM Member

    I have spent a lot of time on this project, and suffered many setbacks along the way. Almost done but wondering if there's trouble ahead? This is a 66cc slant head motor. Found a decent exhaust set up with the expansion chamber. Upgraded the carburetor. Have a reed kit on the way. Milled the head about 8000s. Installed a Jaguar CDI, and just about ready to go. However I've been seeing things that give me concerned about the bottom end bearing. Is there something I should be doing here, or am I going to blow up? Thanks for everybody's kind help. :detective::thinking::ack2:

  2. Fabian

    Fabian Well-Known Member

    The standard crowded roller big end connecting rod bearing is very reliable.

    It will give many miles of good service and it won't blow up if keeping the revs under 5,000 rpm and using a Jaguar CDI.
    The bottom end on my engine with a crowded roller big end is over 5,000 miles old and it's still running well; being installed with a Rock Solid Engines reed valve intake and a Jaguar CDI.

    Be careful about going too high on the compression, because i have previously installed a high compression cylinder head and it caused the engine to diesel with one head gasket.
    I needed 4 head gaskets installed to prevent it dieseling and that was with the Jaguar CDI set to the lowest possible ignition advance curve.
    Nothing will stop an engine blowing up if it's detonating badly or worse still, dieseling.

    I have since reverted back to the low compression cylinder head with one head gasket installed and the Jaguar CDI set to the highest possible ignition advance curve.