Bottom End Torque

motortime

motortime

Member
66 cc / 80cc chinese engine motorized bike
26" wheel front and back
female japan bike
all parts of the engine are stock

the above are my specs of my motorized bike. Can someone give an advice on how to higher the bottom end torque of my bike in the cheapest way? the issue here is whenever I pass a hump, I need to gain speed first by pedaling before pulling the throttle or the engine'll die.

I am eyeing on changing the wheel size and no. of tooth of sprocket in the engine side.
 
no need to change wheel size,changeing gear size helps a lot with hill pulling power,you will lose some top end speed though.a larger gear will pull you uphill better,my bike kit came with a 36 tooth gear,i went to a 40 tooth gear so i could get up my drive way.bike went from doing over 40 mph to just under 40
 
Like Mike said changing sprockets will be the easiest unless you have a smaller wheel already, if you don't have a cruiser bike with coaster brake changing to a smaller wheel will eliminate the side pull brakes unless you have a welder to relocate the mounts.
 
Remember brakes are more important than a motor, you don't have to have a motor but have to have brakes.
 
yeah, my supplier just got new kits with 36T sprockets - I ordered 20, but passed on those sprockets, so he switched them out for 44T

real hilly around here such that even the extra power of 40mm stroke and 40mm intake rules out the 36T for heavier riders

I'm at 150 pounds and one hill behind my house is so steep that it won't allow even a 41T to pull me all the way up.

I did take a few kits with the 36T tho to offer as options for street racers : )
 
A 44 tooth is a must for a 48cc here. The 48cc needs to turn more rpm to get max power. I tried a 41 tooth on mine and top speed was slower.
 
The cheapest way is to get a higher tooth rear sprocket, also, you can get an expansion pipe, as long as you use a long header you will get more low end over stock.
 
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