Stock motor 38MPH

Discussion in '2 Stroke Bicycle Engines & Kits' started by DRK, May 8, 2017.

  1. DRK

    DRK Member

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    Thanks Greg58. I was runnin a 66jet with the needle full rich. Today I put a velocity stack with panty hose air filter on it. It wanted more fuel, so for s#!ts and giggles I gave it a 71 jet and dropped the needle to the middle position. Well, it really liked it. Got 40+ mph, more than once. I'm just havin too much fun! I measured the circumference of my tire and calibrated the speedo accordingly, so I believe it's pretty accurate.
     
  2. PJVolk

    PJVolk New Member

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    I got my stock motor to around 33 flat and 40 on hills. Then I shaved down the head some and I was doing 35-38 flat and bout 50 down hill. I loved it but alas all things must come to an end at some point and for me it was my head gasket blew at same time my piston pin clip came off and took a chunk out of my piston. Fixed it but have had nothing but issued since. Then finally my ****ty gas tank broke open at the mounting studs on it and gas got everywhere. Most importantly but early got into the magneto.
    :-||
     
  3. DRK

    DRK Member

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    Hey PJ; Sorry to hear your having issues. But I'll bet it was fun while it lasted! dnut
     
  4. bigdee

    bigdee New Member

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    ^^^^x2^^^ No way with a 44t sprocket and 26" wheel
     
  5. crassius

    crassius Well-Known Member

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    depends a lot on rider weight, but some 40mm stroke motors might
     
  6. DRK

    DRK Member

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    Just so you know: 44t sprocket....700c wheels....47mm piston....38mm stroke (F80 rod)....
    rectangle exhaust port....38mm intake width....4'' straight pipe (stock exhaust cut off)....no air cleaner....stock nt carb with stock 70 jet with needle set full rich( I took the speed carb off). I did port match the exhaust. I weigh 160lb. On flat level blacktop road, with no wind, the bike will do a hair over 40mph. Me and the bike together weigh 214lbs.I have a cheap speedo that is calibrated to the exact diameter of my wheels, and I believe it to be pretty accurate. I have been well over 40mph on a bicycle before, so I know what it feels like. I did get it to run 38mph with the stock muffler (gutted) and stock air filter mesh element minus the housing.
     
  7. WECSOG

    WECSOG Member

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    I know you want to limit expenditures, but I would really consider an expansion pipe. Some of them are pretty inexpensive. They do more than merely reduce backpressure; they essentially supercharge your engine.
     
  8. DRK

    DRK Member

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    It's not that I don't want to spend money on it, I just wanted to know what I could get out of stock motor. I think if I decide to put an expansion chamber on it I will modify a KX65 or KX80. Thanks for the advise WECSOG, I agree.
     
  9. bigdee

    bigdee New Member

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    STOCK+9000rpm=trouble. Around 20mph/5000rpm,these engines seem reliable. The metallurgy and balancing of these cheap engines is a crapshoot.
     
  10. DRK

    DRK Member

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    ^^^^^^^^^^ 100% True
     

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