gear ratio for non-pedaling start

Discussion in 'Transmission / Drivetrain' started by blckwlfny1, Aug 13, 2010.

  1. blckwlfny1

    blckwlfny1 Member

    If. A 10 tooth sprocket on the motor with a 36 tooth sprocket on the wheel gives. About 35 mph with a gerar ratio of .278 and a 50 tooth sprocket on the wheel gives more hill climbing with a gear ratio of .20 what ratio do you think would allow standing starts with no pedaling for ur avg chinese 2-cycle?

  2. Can you do that with the chinese clutch?
  3. Sterno666

    Sterno666 New Member

    Mine does. It's an 80cc kit from Zoombicycles and I just need a moderate kick-off with my feet on the ground to get going. I can lift the rear wheel and kick start the engine. I think I have a 44 tooth rear sprocket. I'm also a big guy (6'4" 300lbs). I'd imagine a smaller guy wouldn't even need the kick-off.

    You can't just pop the clutch though. you need to feather it out and give it a little gas, like a motorcycle.
  4. I have the same engine, but though it would wear out the clutch very fast doing this. I do start like that even if I'm going very slow, but still moving slightly.
  5. motorpsycho

    motorpsycho Active Member

    both of my bikes can take off just by using the clutch and no peddling.
    one bike is a 66 cc 2 stroke with a 41 tooth rear sprocket and the other is a 49 cc 2 stroke also weith a 41 tooth rear sprocket.
    the big difference is that my bikes are 20" frames with 20" wheels.
    one bike has a 21 inch tall rear tire, and the other has a 24" tall rear tire.
    I can take off with both bikes by feathering the clutch slightly just like a motorcycle, and i am getting around 25-28 mph top speeds.
    i'm a little guy tho...5'6", 155 lbs.

    definitly do not try to pop the clutch and do a burnout or a wheelie...there just isn't enough gear ratio there, and it's very hard on the spokes.
    you can, however. hold the bike back with your feet and gently lift up on the seat with your inner theighs to take some of the friction away from the rear tire and the ground, and do smokey
  6. I'll have to try it. How long have you been taking off like that, and also does your clutch ever wear out?
  7. motorpsycho

    motorpsycho Active Member

    well, one one of my bikes i have been taking off like that since last august (2009) when i first built it. i have about 150 miles on it, and the clutch is fine. i have never had to adjust it.
    the other bike is new and only has about an hour or run/ride time on it.
    my street is on a slight upward incline and i can take off going uphill like that with no problem.
  8. Ok, thanks for the info. Always wished I could do it, didn't realise I actually could.
  9. motorpsycho

    motorpsycho Active Member

    well, it works for me, but it may not work for you.
    wheel size, sprocket size and rider weight may all affect how well this works for you, or doesn't work for you.
  10. I only way 130lbs (only 14) so I have a weigh "advantage" for this purpose. My rims are a bit larger.

    Anyway, I'll try it. If I burn a cluch the parts are cheap, and I have a spare engine (crank bearings are gone)with a good clutch.
    Last edited: Aug 13, 2010
  11. 5-7HEAVEN

    5-7HEAVEN Guest

    Gear ratios calculate like this:

    Engine has 83t/20t = 4.15:1 internal gears

    36t/10t = 3.6:1

    3.6 X 4.15 = 14.94:1

    50t/10t = 5:1

    5 X 4.15 = 20.75:1

    Just so you know.:detective:
  12. Chalo

    Chalo Member

    150 miles? Like an average of less than half a mile per day? Or do you mean 1500 miles?

    Either way, I don't think you can characterize your setup as proven.

  13. motorpsycho

    motorpsycho Active Member

    yes...approx 150 miles, maybe 200 at the most.
    I only ride my bikes for fun and i don't rely on them for every day transportation. I'll buzz them around my neighborhood,(maybe 1-2 miles at a time) or take them to a car or motorcycle show on occasion..that's about it.
    i have 3 cars and 2 motorcycles, and there is no way that i would depend on a m.b. for every day transportation.
    all i can say is that it works for me, and i will keep doing it the way i want.
  14. blckwlfny1

    blckwlfny1 Member what gear ratio do you think will produce a. StAnding start? :)
  15. It didn't work for me and I have the original 44t sprocket. I could start by pushing off with my foot a bit si it was close.
  16. motorpsycho

    motorpsycho Active Member

    you have a 44 tooth sprocket with a 26" wheel, and that makes it a taller gear ratio (more for top speed). trying to take off from a stop with just the clutch on your bike is probably like trying to take off from a stop in 3rd gear with a car that has a manual 4 speed.
    I am running a 41 tooth sprocket on a 20" wheel, which makes it a lower gear ratio. Maybe this is why it works so well for me...because i have 20" wheels, which makes the gear ratio lower.
  17. Yes, I plan on getting a 36 tooth sprocket. I will also be adding some horse power.
  18. 5-7HEAVEN

    5-7HEAVEN Guest

    Ya Can't Have It Both...unless...

    You want a gear ratio for non-pedaling start. You have a 44t sprocket, which does not work for you. Instead of lowering your gear ratio(higher decimal fraction), you're raising it(lower decimal fraction) with the intention of increasing horsepower.

    You will NOT have a gear ratio for non-pedaling start.

    What do you really want? Non-pedalling start, more hp and higher speed?

    You want an SBP shift kit.:idea:
  19. I wasn't looking for a non-pedling start. A little excersize will never kill yeah. :grin5:

    I'm all about speed, and already spent enough money. I will probley get something to shift in the future though.
  20. blckwlfny1

    blckwlfny1 Member

    thank you.
    assuing all internal gearing of the motor to be constant and the 10-tooth sprocket in the driveshaft to be a constant as well, the only variable in the gearing would be the wheel sprocket. it may not work for numeric hp and torque calculations off of the drive spline itself, but, any constant on both ends of a relative equasion can be cancelled out to simplfy the mathematics. ...And beleive me i can use all of the help i can get. :ack2:
    i wasnt so much interested in the numbers. just an opinion of what might push my but down the road .
    Im trying to fabricate a mid-drive transmission (to preserve the coaster brake as well as the vintage left-hand-chain drive) and i will be trying to shoehorn sprockets into some tight spaces so i have to design it baed upon the size of the components. Soooo...I'd rather not base its low end upon some arbitrary number which i may have to change. Does anyone think the gearing equivalent of a 60 tooth sprocket (1:6) ratio) would do it ?