Something Good Happened Today

Discussion in 'Motorized Bicycle General Discussion' started by karryhunt, May 2, 2010.

  1. karryhunt

    karryhunt New Member

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    After about 200 miles and the 1/-1/2 gallons of 16:1 mix my maximun speed has never exceeded 24-25 MPH not that I didn't have pedal to the metal. Today at around 18 MPH, I decided to see if I could beat the old record of 24 MPH so I opened her up and she got right up there to 24 MPH. Trying to get the last bit of go out of this thing, I was rentless and held the throttle open for about 10 -15 seconds longer than normal. All of a sudden, without warning, this little engine became a monster and screamed louder and longer than I have ever heard her before. The speed climbed steadily from 24 MPH up to almost 30 MPH. (see photo)

    My question........Is this little engine telling me she wants to put on her big girl pants now that the break in period is just about up or is it a sign of somehing bad about to happen?


    Speed record.jpg
     
  2. mapbike

    mapbike Active Member

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    What tooth # sprocket you running?

    I cruise at 28-30MPH and top out at 38MPH and I'm running a 41T & 66cc engine, if all is set up right and you have a 44T which is very typical you should be able to hit about 35MPH when it is broke in good after about 50-75 miles on it with 40:1 synthetic oil mix.
     
  3. fang_x

    fang_x New Member

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    if you want more power try removing the Baffle, its the little piece of metal on the end of the exhaust pipe, the biek becomes a bit more loud, but its totally worth it, speed and accel increases

    i used to have the same thing as you, then i removed the baffle and it was 100% better
     
  4. hambro

    hambro New Member

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    I was just wondering how many different variations there are on those stock kit mufflers. I myself have seen about 4 different types and I know for a fact that some are way more restrictive than others. If anyone has any info on this I'd love to know.
     
  5. Cabinfever1977

    Cabinfever1977 New Member

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    I guessing you have a 44t sprocket and 30-32mph is around the top speed,but at those speeds with that sprocket, the engine is also doing very high rpms. If you want to run at those speeds for a long time,you might want to get a smaller rear sprocket, and your engine will run at lower rpms and last longer. you also might want to change your oil/gas ratio to atleast 20:1 or 24:1 or higher.
     
    #5 Cabinfever1977, May 2, 2010
    Last edited: May 2, 2010
  6. corgi1

    corgi1 New Member

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    Did you try the run again,and did it react the same way ? or does it just wrap to 30 w/out the 24mph terrace?
     
  7. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    Wow Harry, er I mean Karry, that was almost like a Penthouse letter.
    Yes, uh, "time for the big girl pants".

    Big girl pants being a 32:1 mixture... and maybe get some Kleenex.
     
  8. BarelyAWake

    BarelyAWake New Member

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    karryhunt - about 200 miles ya say? I'd lay long odds that you've simply reached that wonderful point where yer engine has fully broken in and is finally runnin' right (^)

    Now jus' continue to ride the bejabbers outa the thing! .wee.



    http://motorbicycling.com/f13/catalytic-converter-mufflers-15857.html & http://motorbicycling.com/f13/catcon-muffler-mods-17098.html

    But TBH even if you've the type kit muffler that can be drilled to reduce back pressure, it's a marginal gain at most with the predominant change mostly a placebo effect as louder seems faster. Reducing back pressure is mostly a 4 stroke thing as two strokes need some amount of back pressure to perform properly - reduce it too much and the fuel/air charge can pass right through the combustion chamber before ignition. This is why an expansion chamber exhaust system is so important on a two stroke - it "times" the back pressure into a pulse, essentially making it the exhaust valve we haven't got.

    Ofc some kit catalytic mufflers have too much back pressure, to the point where it's far too restrictive - but if you're after a true performance gain, replacement with an expansion chamber is the only real option no matter which kit exhaust you've got.
     

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