79cc gear ratio?

waynesdata

Active Member
Jul 10, 2017
254
107
43
42
Most kits I have seen have the same default gear setup.

Motor Sprocket 11 tooth
Jackshaft Input Sprocket 22 tooth
Jackshaft Output Sprocket 9 tooth
Wheel Sprocket 44 tooth
Tire Height 26“

Is this gear ratio ok?
 

Attachments

Jan 21, 2015
610
21
18
Portland, Oregon
Most kits I have seen have the same default gear setup.

Motor Sprocket 11 tooth
Jackshaft Input Sprocket 22 tooth
Jackshaft Output Sprocket 9 tooth
Wheel Sprocket 44 tooth
Tire Height 26“

Is this gear ratio ok?
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
Staff member
May 25, 2008
12,775
106
48
55
Moosylvania
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?
 

waynesdata

Active Member
Jul 10, 2017
254
107
43
42
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.