66cc sbp pipe tuning power w porting help please

Discussion in '2-Stroke Engines' started by sublunacy, Dec 15, 2013.

  1. sublunacy

    sublunacy New Member

    i have a 66cc w reed and 15mm walbro.
    im trying to move the power back up after settling on a long manifold for low rpm but the engine wont get on the pipe like it would w a 4 inch shorter manifold.
    am i on the right path if?

    i port ex/tranfers to bring powerband back up to higher rpm???
    Last edited: Dec 16, 2013

  2. HeadSmess

    HeadSmess Well-Known Member



    its either use reeds, or use the extended manifold. not both.
  3. jaguar

    jaguar Well-Known Member

    the pipe works in harmony with the porting.
    Use the standard exhaust, port for the desired peak RPM, then install expansion chamber and set the header length for the max rpm you want. Longer limits max rpm.
  4. sublunacy

    sublunacy New Member

    ok great. i edited my question for clarity. was just wondering about something. my topend rpm is perfect right now as it sits.
    when i go shorter manifold to raise hp i should add some stinger length then to achieve the desired redline rpm? that sounds easy lol?
  5. jaguar

    jaguar Well-Known Member

    hate to say this but I think you have many confused ideas about how things work. You need to take the time to study this stuff.
    Click on my signature link and read read read...
  6. sublunacy

    sublunacy New Member

    with pipe fine tuning 2 strokes? yes thats what every one is forced to do w our custom gasbikes. so for the first time/the best pipe is my own. i saw your bike jaguar sitdown. thanks
  7. jaguar

    jaguar Well-Known Member

    sit down? I guess you think this is a beauty contest or something.
    I spend all my time improving function, not beauty.
    Ride my bike and then lets see if you still want me out of the way.
  8. Fabian

    Fabian Well-Known Member

    That line is analogous to being married for ten years.
  9. Pablo

    Pablo Motored Bikes Sponsor

    Isn't it like 4:30AM there?
  10. Fabian

    Fabian Well-Known Member

    It's 7:30AM here. I've finished work around an hour and a half ago.
  11. HeadSmess

    HeadSmess Well-Known Member

    nope. would have been about 7 am :) if the posting time and my time are correct...

    mmmm, vladivostok time :)

    otherwise. ha ha ha ha.

    but, really...other than clicking on links, it is the way to go...

    set up for reeds, ie, piston cuts.
    run a stub exhaust, no tuned pipe at all. tweak ports for desired grunts and rpm.

    attach pipe, fiddle with HEADER length until desired RPM and pipe are in synch... and desired grunt will increase.

    retune carb to suit new setup.

    (im leaving the door open here, but... we shall see)

    you cant have low end and top end out of the same engine, with a 2 stroke.

    even if a lil 37cc polini or similar can pull 110 kg on a single gear and get to 120km+ in stock trim...

    i dont consider 8000rpm as being terribly fast, when it comes to an engine. still got twice that on my moto before redline...

    on a lathe but, even 1000 is scary...
    FurryOnTheInside likes this.
  12. Fabian

    Fabian Well-Known Member

    250 rpm on a helicopter rotor head is scary.
  13. HeadSmess

    HeadSmess Well-Known Member

    especially how each blade is hanging off just one bolt!

    them there bolts are called jesus bolts! cus, jesus, you dont want one to break!