Top Speed, 80cc Chinese motor? what is the record?

Discussion in 'Motorized Bicycle General Discussion' started by scottcason69, Apr 26, 2013.

  1. Davezilla

    Davezilla New Member

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    I definitely agree on the difference between a full throttle run and the pure torture of the race tracks where rpm needs to stay up by any means possible so heat goes up the same but with less opportunity to cool the engine...

    Wow Map if yours is running 8950 to hit 52mph your engine probably spins as fast as mine if they were both geared the same... Compression is important on a 2 stroke for low rpm torque and power, but as the rpm's climb up it becomes less important so the power's probably about the same as mine at those rpm's too...
    I know my static compression ratio is 12.7:1 but the actual is quite lower since the actual is measured from the top of the exhaust port instead of the bottom of the stroke like a 4 stroke engine, this ratio varies tho on the 2 strokers because as rpm increases and if an expansion chamber is used the ratio can go up a few numbers so it's more like a virtual compression ratio that falls somewhere between static and actual.
     
  2. mapbike

    mapbike Active Member

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  3. SpecializedMountainMoto

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    I was thinking the sunlite monarch replica actually
     
  4. mapbike

    mapbike Active Member

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    All I know is that that engine sounded like it was gonna take flight or blow like a stick of TNT at top speed....LOL..!

    I may have just got lucky with port timing and such on it since I did nothing scientific really, just a few measurements and guess work with some calipers, some filing and some dremel work, I had planned to take the deck height down some, but then just decided to see how it would run without changing it.
     
  5. SpecializedMountainMoto

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    Pretty good price on that one tho
     
  6. Davezilla

    Davezilla New Member

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    Either front end would look great on that bike... What pipe are you running? it looks a lot like the KTM pipe I got before I cut it up and rearranged it...
     
  7. mapbike

    mapbike Active Member

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  8. Davezilla

    Davezilla New Member

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    That's one good thing about reading in the forums for porting, a lot of people post the "if you cut up a milimeter here, down a milimeter there, go this much wider here, and clean out this area" you can actually get a nice fast engine with good power without all the calculations... If you go back and measure everything when it's time to rebuild it I bet your timings and durations are really close to what we've been talking about a lot these last few days..
     
  9. mapbike

    mapbike Active Member

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    I like that pipe also and was thinking the same about it looking like the KTM pipe
     
  10. Davezilla

    Davezilla New Member

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    Yeah.. some of those springer froks can cost more than the rest of the bike... but they do look cool and it's worth it if it makes the bike handle better and ride safer...

    The front end I got on mine costed more than the bike it went on too.. and I got mine dirt cheap...

    This one has been modified to fit my needs some, but this setup usually sells for upwards of #200 if you find a set in good condition...

    [​IMG]
     
  11. Davezilla

    Davezilla New Member

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    Here it is on the bike... this is the one that does 41 mph with the 44 tooth rear... The pipe is ugly and dented but it works great, this pipe started life on a KTM 50...

    [​IMG]
     
  12. mapbike

    mapbike Active Member

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    That could be very true Dave, I did take more time on everything with this engine than I had on the others, I do think I could get a little more out of that jug and piston combo with a better exhaust and a bigger carb along with having the jug shaved down to increase the compression, even if the top speed wasn't that much more, think a few extras would help get it there quicker, the 52 MPH was going down a slight declining area on the road also, it wouldn't hit that speed on the flat and was more in the 49-50 mph range as long as no head wind was involved, that old bike is a little heavy and me at close to 220 at that time was a lot to ask of that little engine, I was surprised it did as well as it did honestly.
     
  13. SpecializedMountainMoto

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    That pipe is the kx65
     
  14. mapbike

    mapbike Active Member

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    Those are really cool looking forks... I liked them the first time you posted a pic.

    I'd never seen them before, but that isn't surprising since I'm not much of a man of the wold and just a small town country fella...LOL

    A lot of the high end stuff out there I know nothing about and never even seen before.
     
  15. SpecializedMountainMoto

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    Wow that's a crazy looking springer, does it have dampening?





     
  16. mapbike

    mapbike Active Member

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    Cool, did it take much modifying to get it hooked up other than the flange?
     
  17. Davezilla

    Davezilla New Member

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    If it can pull 49 to 50 on the flats then it's definitely making some good power, even with no head wind, there is quite a bit of wind resistance at those speeds.
     
  18. SpecializedMountainMoto

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    Nope cut off the flange and used a sbp one, added the end piece off an ebay pocket bike pipe. When I had just the pocket bike pipe it was so restricted it would only hit 41mph
     
  19. mapbike

    mapbike Active Member

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    Very true..

    I did about have my chin on the tank and had at least 2/3 of the seat sucked up my back side so that might have help buck a little of the wind....LOL!
     
  20. Davezilla

    Davezilla New Member

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    It has dampening now... originally these used one of those polymer spacers to absorb the shock etc, but those polymers wear out and melt like a rubbery waxy mess... What I did was order a go kart shock that's oil damped and then took the spring off in favor of a lighter tension spring made for this fork to replace the original polymer. I tried it out with just the spring and it was a little bouncy and bottomed out too easily so I had to find a shock that was the right length then open up the eyelet holes to fit the fork's hardware. End result is a very nice handling ride that's also very stable at higher speeds and can take the unsuspected potholes etc..
     

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