Twin engine??

Discussion in 'Performance Mods' started by Evil_Genious13, May 18, 2015.

  1. has anyone successfully built or even seen a motorized bike with TWO frame mounted engines (Either 2 or 4 stroke) both sending power to the rear tire? I have an idea on how to do this but I can't find any examples of this already being done. I can't be the first/only person to want to do this but there seems to be extremely limited information out there. Any and all help and knowledge is appreciated!!

  2. darwin

    darwin Well-Known Member

  3. butre

    butre Well-Known Member

    I was going to do one a while back with twin case inducted china girls geared for bombing some local trails but ended up way over budget and had to turn the project into something a little simpler. it was going to be electric start and the engines would be connected simply by a custom jackshaft assembly, which would have gone to a rear 3 speed internally geared cable shift hub.

    It's an expensive project that requires lots of custom fabrication, and you're better off just getting a more powerful engine like a KTMC 50 or a honda ohv clone
  4. The_Aleman

    The_Aleman Active Member

    5 or 6 years ago there was a couple of guys who put _3_ chinagirls on a trike. I had some pics, but redid my system recently, so they're not on-hand.
    I dunno how the trike did in the end (details are scarce unless you're an insider), but I do know this immutable fact:

    Double the chinagirl, double the probrems. Same with tripre. The chinagirl was designed over 50 years ago and it can be finicky if you get needy.

    Over the years there's also been some poor dudes putting 2 chinagirl cylinders in one case, attempting to make a *******ized V-twin.
    None have been successful outside of prototype stage that I know of, so far. (I try hard to keep up with all MaB stuff, and always open to corrections)

    If you need that much power on a bicycle, most sane folks would tell you you need a motorcycle or something above a MaB.
    My own opinion, not that you asked for it but here we are in a freegin forum, and me having done this thing since '06, and gone 40+ I spose I'm gonna say it lol
  5. Large Filipino

    Large Filipino New Member

    This guy posted his bike on Facebook a few months back. It's so hard to find the video now.
    It's the little things that make this bike sick from the teapot exhaust to using utensils all over
    to the use of two wheelchair wheels for the front wheel.
    You can stare at this for hours and still not find everything.
  6. Ra1977

    Ra1977 New Member

    GREAT IDEA. The goal of the twin cylinder should be for low end torque. Such as a MB with a sidecar, Or a trike pulling a trailer. Speed should be the secondary or last goal. Like someone said 40mph is plenty fast for a bicycle.
  7. HeadSmess

    HeadSmess Well-Known Member

    thats about the best reason not to do it. theres far better engines with a lot more power in a smaller/lighter package that work without any of the hassles of dealing with two engines...
  8. 45u

    45u Active Member

    They use to use twin engines in drag racing but not longer do as it is VERY hard to get both motors in sink and is why the quite using twin engines as they found they can go faster with one in sink engine then two out of sink.
  9. butre

    butre Well-Known Member

    it's also a pretty good reason to do it
  10. AutOtaku

    AutOtaku Member

    Ive run into a photo of a guy who used two china girls and made a parallel twin on anouther MB forum....dont have the link though. BikeBerry has a photo on their facebook of a twin engined bike with a frame mounted 2-stroke and a rack mounted 4-stroke.

    Why not put two pistons in one cylinder? Its been done before and would be the best solution.....
  11. butre

    butre Well-Known Member

    two pistons in one cylinder? are you referring to a twingle? there's no advantage to twingles. they're heavier, more expensive, and more complicated.
  12. AutOtaku

    AutOtaku Member

    If you just wanted two pistons on one bike, that be feasible other than that your right
  13. Steve Best

    Steve Best Well-Known Member

    That would work with both going to 2 sprockets on a single jackshaft.

    AutOtaku likes this.
  14. AutOtaku

    AutOtaku Member

    Though wouldnt a big problem with that be having both pistons hit TDC at the same time? Ive seen that brought up.....
  15. Steve Best

    Steve Best Well-Known Member

    With both sprockets feeding a jackshaft you would never have both engined sync'd in any way. It really would not matter much. Occasionally vibes would be bad and occasionally they would be better. 2 independent motors working side by side.
    Frankfort MB's likes this.
  16. HeadSmess

    HeadSmess Well-Known Member

    twingle isnt the only type with...hang on...twingles still use two cylinders, dangnammit!

    mmm, opposed piston like a doxford or napier deltic... sheesh. then you got two crankshafts to deal with...

    biggest issue i believe the twingles had was the fixed conrod, always had to flex a bit... why they never tried a forked big end, god only knows...

    but they do have good scavenging characteristics, as one cylinder has the exhaust, one has the transfers... bit of ingenious porting /synching and you can run (finally!) forced induction that actually works! (thinking about plans i have somewhere for a model boat...two contra-rotating engines in one case with a combined head... no torque reaction, and suited to twin propshafts... otherwise, silly...)

    still, way too much effort for the gains... oh, they were mad, 50+ years ago when every guy had a lathe and tried out new ideas...
  17. Steve Best

    Steve Best Well-Known Member

    I didn't know about the Doxford or Napier Deltic, thanks. I worked on an Allstate Twingle when I took shop in the 70s.
    I saw a Junkers Jumo 6 cylinder opposed piston diesel AIRCRAFT (!) engine in a museum in Ottawa.
    800hp and light enough to fly. Wow.

    These engines are cheap enough and virgin canvass for many ideas. Wonderful place to learn.