79cc gear ratio?
- Thread starter waynesdata
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- 79cc gear ratio transmission
TheNecromancer13
Active Member
That gear ratio is about 9.78:1, way too steep for a 79cc predator. You'll burn up your clutch and won't be able to go up hills. I have mine geared at 13.1:1, I weigh 155 lbs, it tops out at 40 mph. I wouldn't recommend buying the kit though, most of the parts are **** and it doesn't include everything you'll need to build the bike. Here's what I do: https://www.instructables.com/id/79cc-Motorized-Bicycle-From-Scratch/
Dan
Staff
Wayne, I misread and messed up the math. Necro is 100% correct. But do love that jackshaft. I can't make one from scratch for that price ($99 as of this post) Really is stout and well finished. I deleted my bad advice so as not to cause confusion.
I just use a larger rear sprocket. 54T gives you 12:1.
9:1 would work but is not fun at take offs. Shudders real bad. I did not burn threw any clutches but am sure I would have eventually and I was using less then 9.78:1 .
What did you decide on doing?
I just use a larger rear sprocket. 54T gives you 12:1.
9:1 would work but is not fun at take offs. Shudders real bad. I did not burn threw any clutches but am sure I would have eventually and I was using less then 9.78:1 .
What did you decide on doing?
waynesdata
Active Member
I do not know yet. I got a frame from gasbike when I ordered wheels. Will need to find out if the four stroke mounting hardware will clear my built in mount.
TheUserMac
New Member
See I saw that kit and their out of stock does anyone know where I can order another I don't mind buying a separate sprocket to correct my gear ratio
Sidewinder Jerry
Well-Known Member
In order to get close to 40 mph using 13.1:1 at 6000 rpm you'd also need 29" tires.
(6,000×π×29)÷(13 1×1,056)=39.5151747719
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Sidewinder Jerry
Well-Known Member
The recommended safe rpm for these stock engines is 4000 rpm. With your setup on 26" tires your speed will be 31.6 mph
(4,000×π×26)÷((44÷9×2)×1,056)=31.6431078228
Sidewinder Jerry
Well-Known Member
Your ideal setup would be to get a fixed geared IGH for a jackshaft transmission and run 11/36;14/56. This'll give you the following reductions.
1) 17.45:1
2) 13.09:1
3) 9.82:1
Get a tachometer. If at WOT you're going over 4000 rpm shift to a higher gear. If at WOT you drop below 3000 rpm shift to a lower gear
1) 17.45:1
2) 13.09:1
3) 9.82:1
Get a tachometer. If at WOT you're going over 4000 rpm shift to a higher gear. If at WOT you drop below 3000 rpm shift to a lower gear
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TheUserMac
New Member
Any links so I can cheat the researching process?
Sidewinder Jerry
Well-Known Member
Any links so I can cheat the researching process?
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Is it possible
Why not instead of getting a jackshaft to use the shifting gears flip the motor around and not even worry about a jackshaft wouldn't the sprocket be going in the right direction and then you can maybe use a 3speed or better internal hub shifter would that work
motorbicycling.com
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