40 MPH Club

Discussion in 'Motorized Bicycle General Discussion' started by massdrive, Aug 10, 2014.

  1. Semaj

    Semaj Electric Enthusiast

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    I am 100% digging the green and white! Thats a great color scheme you got going on there :D
     
  2. LandSpeedRecord

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    Thanks! It is starting to come along. I hope when it goes back together this time I start to see the results I'm looking for. It was finally starting to feel and sound like a proper two stroke with a smooth hitting power band pulling cleanly to the top with no 4 stroking or flat spots. It's taken a lot of work.
     
  3. Tony01

    Tony01 Active Member

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    Yo! Just hit 40s. Tried my old single speed clutch with the new final drive ratio... And this is what I get with 7.33 total ratio on 26" tires. 100rpm=mph. The motor wanted to rev more (1500rpm) but there was a big slow truck in front of me :mad: acceleration is embarrassing

    Going to try a later engagement... And bump up that idle to 2k laff
     

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  4. LandSpeedRecord

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    Welcome to the 40mph club beginner01! I will be trying to re join soon with a 49cc Huasheng 4 stroke on a beach cruiser. It may turn out to be a bigger challenge than Bonneville with a China Girl ha ha.
     
  5. Davezilla

    Davezilla New Member

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    Welcome to the club beginner!!
     
  6. Davezilla

    Davezilla New Member

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    Coaxing 40mph out of a 49cc 4 stroker will be a good challenge... it can be done but won't be quite as easy...
    With some careful port work, bigger valves,bigger carb, a tuned pipe (stepped type header), and a cam (if available ) and give it lots of compression and it should make it, best bet would be to set it up to make lots of top end power, lots of rpm, and gear it down and/or find a way to make a cvt work and 40mph should become fairly easy to reach. You could run it on methanol or even a nitro blend will also help.
     
  7. LandSpeedRecord

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    The cam is available and I will port it even though they say not much can be done. Compression is fixed on the Huasheng, but I have a couple ideas that might work. I have an aluminum intake manifold partially built out of half a Briggs V-twin manifold, I'm sure I will have some work to port match it and line up the bolt holes. I have read up on header designs and that should be straight forward. And you know I like nitro blended with methanol, the China Girl took to it really well. If the Huasheng seems strong enough I may try the same percentage I ran in the CG since I have baseline jetting math that should be close. I will have to blend my own though. With the 2 stroke I took the easy way out and bought off the shelf R/C fuel but it had a ton of castor oil in it and I don't want or need that in the tiny thumper.
     
  8. Springfieldscooter

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    Off the shelf?
    How did it affect the jetting?
    Did the fuel alone increase top speed over premium pump fuel?
     
  9. LandSpeedRecord

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    There is a huge variety of pre blended nitro fuel available for R/C cars and planes. Everything from 5% up to 50% nitro to methanol blend but they use huge amounts of castor oil in the blends. I was able to make it work with the emulsion tube drilled as far as I could then one size bit up from that on the jet with an RT carb fed by a Briggs V-twin pulse pump. You have to try to achieve 6 times the fuel flow rate of gasoline. It actually burns cooler and makes roughly 3 maybe close to 4 times the combustion force of gas. It's a very quick way to explode engines obviously. Mine held together for a few wide open passes on our test road. I have a balanced crank and tapped the cases to 3/8 and had grade 8 bolts ran down thru the head for studs.
     
  10. LandSpeedRecord

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    The whole set up wouldn't idle or even run below probably about 3500 rpm but it made a bunch of power at wide open throttle and high revs. I only tried the 20% blend but with a bunch of trial and error could find a mixture that would run ok I'm sure. I just needed wide open top speed power so that was all I tried for. Happy Motoring!
     
  11. Tony01

    Tony01 Active Member

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    Don't do the CVT. If you can hook up a shift kit that would probably get you to 40 on a long enough straight. What I have found is that the CVT sucks up a good amount of energy and limits the engine rpms to the shifting rpm- so if it engages around 2200 shift rpm will be around 3200, and the motor will never rev higher. Even if it did rev, you're still fighting the mechanical losses of the belt.

    When out on the road I guess I forgot to tighten the crank bolt and my cvt eventually undid itself, 2mi from home. Spent an hour treasure hunting for one part of it with no luck. Ended up hiding the bike in the bushes and came back to that spot the next day with another transmission- MT belt clutch, hoping it would work to take my bike home. First impression: acceleration super slow. Clutch lockup wayy too early. But once it fully locks up with the bike going about 20 mph, then the motor will rev to 4500 and the bike is extremely responsive.

    Although my original cvt high gear ratio is the same as the mt clutch.. The losses of the belt prevent it from revving. I am experimenting with changing the cvt engagement to 3000, and 3300. Hopefully that will let the shift rpm increase closer to 4500. Also, I will change the rear final drive sprocket from 12t to 15t and try to join the 50mph club! xct2
     

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