ATTN: New 66cc engines with longer conrods and thinner aluminum on cylinder jugs.

Discussion in 'Performance Mods' started by lazylightning@mail.r, Oct 6, 2013.

  1. lazylightning@mail.r

    lazylightning@mail.r Active Member

    There is a rod length problem with the 66cc now. Alot of the new engines are coming with longer rods and this can mix you up when changing parts. For example the new 66cc's that have appeared everywhere here have longer connecting rods. Instead of being 85mm from center to center, they are now all 89mm from center to center. So you have to buy the new pistons that go with them. They have the piston pin hole 4 mm higher up. These new engines have much less metal on the carb and exhaust mating surfaces on the cylinder jug. So your out of luck if you wanted to widen the exhaust to 25mm round on the outer surface for example. It looks like they are trying to save on aluminum, so the walls are probably thinner at the transfers and will limit your ability to open up and deepen those transfer channels when porting.

    This problem should be paid attention closely by vendors to make sure their Chinese partners or middle men thereof do not send them this CRAP!

  2. bahramu

    bahramu Member

    Is there a way for me to measure how long my connecting rod is without splitting the case? I received my new 66cc 3 weeks ago and I'm trying to determine port durations but I need to know the connecting rod length

    Nevermind, people have known the 66cc has a 89mm conrod for a while. I've just mapped my 66cc cylinder using 40mm stroke and 89mm conrod. My port durations match what others have measured on a 66cc except for the intake
    Last edited: Oct 11, 2013