New Engine Today!!

Discussion in 'General Questions' started by dondupuis, Apr 14, 2015.

  1. dondupuis

    dondupuis Member

    Hello All.

    Today i just installed a SkyHawk GT5A
    claims to be rated for 2.75 HP.
    This is way more fun than my old one.
    all upgrades other than the air filter.
    32T rear sprocket.

    it's pretty fast.

  2. bluegoatwoods

    bluegoatwoods Well-Known Member

    Glad to hear it.

    Pics of the bike would be good. We can't get enough of that around here.
  3. Slogger

    Slogger Member

    Pulling a 32 tooth pretty good, huh?
    That's very cool. Having a new engine to fool with makes it seem like Christmas! We need a picture to appreciate it, man.
    Have fun, good luck with it!
  4. dondupuis

    dondupuis Member

    GOPR0885.jpg GOPR0891.jpg

    I am working on a new expansion chamber. Engine has been port matched.
    Stock carb.

    Next install will be shift kit and 16g dry shot. looking to break 150kph (just waiting on the mail)

    future plan for the summer is to install this.. 73fd_12.JPG
  5. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    Oh, no, not another noob who is gonna turbo charge a 2 stroke China girl. :jester:
  6. butre

    butre Well-Known Member

    oh lord
  7. dondupuis

    dondupuis Member

    im a noob to these chinese bike engine kits, but not at turbo charging small engines. ;)
  8. butre

    butre Well-Known Member

    I'd put money on that being an exaggeration, small displacement 2 stroke engines are nearly impossible to turbocharge.
  9. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    Oh really, what "small" engines have you turbo charged?

    I must have seen 20 people claim they were going to turbo charge a China girl
    since 2008.
    It is never going to happen.

    Big Boy Cycles did turbo charge a 110 cc 4 stroke and it was a very complicated
    project to build.
  10. dondupuis

    dondupuis Member

    i have installed these turbos in 49cc pocket bikes in the past. no troubles with these at all. these things are tiny and these engines don't have any trouble spooling them up.
  11. coyote888

    coyote888 Member

    if that turbo actually works i will be adding one o.o im already working on a liquid cooled head for my bike. i wouldnt be the first to do it but i want one and cant find a place to buy one... sooo XD
  12. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    Really, lets see some pics of your turbo charged 49cc pocket bikes.
  13. dondupuis

    dondupuis Member

    it's been a few years if i come across some old photos or video ill post them, but im not the first to turbo a pocket bike.

    none the less. the bike will get a turbo and i will share with everyone.
  14. The_Aleman

    The_Aleman Active Member

    Sounds like a Chinese grenade waiting to happen...
  15. KCvale

    KCvale Motorized Bicycle Vendor

    An expansion chamber works by forcing unburnt fuel in the exhaust back into the cylinder via a resonance wave.


    Properly tuned it makes these little 2-stroke engines extremely efficient.
    How you might be able to tune forcing more intake in as well from the feeble exhaust flow via a turbo charger is a mystery to me but not what really got my attention...

    It is you 'looking to break 90 MPH' on that knobby tired used ~$200 mountain bike that really cracked me up...
    Heck, that bike would self destruct before you even got to half that speed and blow you off it before if it didn't.

    Do have any clue how fast 90 MPH really is?
    90 mile per hour wind is hurricane force.
    Heck, 90 in a nice car is fast, ever rode a real motorcycle 90?
    Put you hand out the window in a car 90 and see how it feels.

    So back to reality.
    A shift kit helps as does an expansion chamber exhaust and good spark plug, but shoot for high 30 MPH speeds at most is my advice.
    steveanson likes this.
  16. dondupuis

    dondupuis Member

    I know it seems like a pipe dream. and yes i have done 90 before. live for speed. that bike right now will easily do 45 mph with the single speed 32T rear sprocket. @ 3300 rpm. i don't think it's impossible to double this speed. Are these engines not capable of 8000+rpm with the right tuning?

    I totally agree about the bike, this build will be done in a better bike.
    45 on this thing with my motocross gear is scary.
    specially when a large truck gets beside you and starts pushing you around.. lol.

    I don't really plan to do 90 all the time. but it's nice to know it can if i wanted to.
  17. butre

    butre Well-Known Member

    I think I understand what's happening. you're using a bicycle speedometer. at 3300 RPM you should only doing 24 mph with a 32 tooth rear, unless you're falling down a cliff you're not doing 45 mph at that engine speed. a bit of port work, a bit of good proper expansion chamber (not the cheapo hydroformed ones you get on ebay), and a carb that's worth a damn and you might hit 50 with that gearing.
  18. dondupuis

    dondupuis Member

    this engine has port work and i have built a custom expansion chamber for it. i have a tach installed on the bike and get speed from bike computer, GPS and car beside me. 45mph and i probably pulling 50mph on nitrous. I am 124lb rider.

    this is not a build looking for reliability. just looking to make this as fast as it can go. I have plenty of spare parts and time.

    I think if anything in incorrect it's the rpm from the cheap chinese tach.
    Last edited: Apr 24, 2015
  19. dondupuis

    dondupuis Member

    Shift Kit install today..
  20. 2old2learn

    2old2learn Member

    Can't wait to see how it performs with a shift kit.. At those speeds, wear a good helmet!