Cant seem to pass 30mph

Discussion in 'High Performance Bicycle Engine Tips and Motorized' started by BlazeAZ314, Jan 6, 2017.

  1. BlazeAZ314

    BlazeAZ314 New Member

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  2. ultralight01

    ultralight01 New Member

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    You removed your air filter? That will destroy your Carb and hurt your engine. Unfiltered air is like sandpaper to an engine. Put a metal mesh filter on it.

    The performance muffler will help. There are a ton of mods available. but don't expect over 35-40. There is a peak engines hit and once they're there it's hard to go faster without a jackshaft kit and lots of mods and $.

    These bikes are often only legal if they stay below or at 20mph. If you want to go fast, like 50mph, buy a jackshaft kit to use the bike gears or get a different engine AND a jackshaft.
     
  3. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    What ratio are you mixing your gas?
     
  4. TheNecromancer13

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    First off, don't run it without the air filter. Second, that expansion chamber you bought looks rather tiny. You'd be a lot better off making one yourself.
     
  5. sbest

    sbest New Member

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    I was able to get just barely over 40mph with the 44t sprocket and stock carb.
    1) port match the exhaust pipe flange and gasket to 19mm (pipe pictured not so great)
    2) Modify the head to have a 2mm squish band right out to the outer diameter.
    3) Eliminate the headgasket with teflon tape and shim the basegaskets to get 0.030" squish.
    4) Widen the bottom of the intake port window and the top of the exhaust port a couple of mm on each side.
    5) run your chain just barely loose and as straight as you can.
    6) Tune your main jet to get the plug a nice tan colour, and your needle to suit.

    This will put you pretty close to 40mph and plenty of power on the hills.
    Go careful, the proof is in the details.

    Steve
     
  6. Tyler6357

    Tyler6357 Member

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    I was going to say the same thing, that expansion chamber looks small with a long header, it might help on the low end but I don't expect to get much on the high end with that thing.

    brnot
     
  7. mike carter 2

    mike carter 2 New Member

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    that is the same chamber that came with my gasbike gt80 kit .its junk, the flange (the part that bolts to the exaust port) is way to small.about half th size it needs to be .i first cut it up and tried to use just the chamber part useing 1 inch conduit bent and shaped for my header.i also dremmeled out the flange to make it larger.it helped but still not rite .i ended up modding a 1979 suziki rm 80 chamber using a cr machine header,made all the differance in the wourld.went from about 25 to around 40 instantly. before you install it look at how porely it matches to the exaust port
     
  8. mike carter 2

    mike carter 2 New Member

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    im sorry i was so blunt earlyer . didnt mean to seem like that.i did a lot of reasearch on this website to make my desions to build the way i did.there are a lot of people on this site that take no greater pleasure than helping people like us,newbies.my advice is to read as much as you can on this website ,figure out who have the knowldge you need and talk to them , pulse a big shout out to all the people that helped me without even knowing it !!!!!!!!!!! m carter
     

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