I've got a 49cc engine from thatsdax and a 36 tooth sprocket. I've got the motor on a 700x38c bike. I have 150+ miles on the motor and consistently ride at 25mph and with a top speed of 28mph. I weigh 160lbs and when "pushing" the bike I can tell the rpms never get anywhere near peak. Using calculations from on gearing the rpms are sitting around 4500 at 25mph and I know the bike has more to give. It seems the engine doesn't have enough power to get it to the 5500+ rpm range. Would I be able to increase both bottom torque and increase top rpms and keep the same top speed with a 44tooth sprocket?
49cc and 36tooth
- Thread starter jjm86m
- Start date
I am running a 40T on my 50, and I have experience with a 36T on my 80.
IMO a 36T is a little too tall for a 50. My 50 will easily cruise @ 28 mph all day long. Under the right conditions it will pull up to about 33. The record so far was 34 going downhill.
It has about 1500 miles on so far. Performance mods are few. Slightly opened stock exhaust, with a MM shorty intake ,and performance air filter. NGK BP5HS spark plug and a 68 jet.
It will pull a hill fairly well with this set up. It takes a pretty steep hill to drop the speed below 20 mph.
China Girl and Proud of It - YouTube
Fastest Motor Bicycle in Farmers Branch. - YouTube
IMO a 36T is a little too tall for a 50. My 50 will easily cruise @ 28 mph all day long. Under the right conditions it will pull up to about 33. The record so far was 34 going downhill.
It has about 1500 miles on so far. Performance mods are few. Slightly opened stock exhaust, with a MM shorty intake ,and performance air filter. NGK BP5HS spark plug and a 68 jet.
It will pull a hill fairly well with this set up. It takes a pretty steep hill to drop the speed below 20 mph.
China Girl and Proud of It - YouTube
Fastest Motor Bicycle in Farmers Branch. - YouTube
I run a 55cc with a 36 on a 26"er. it's not a mountain climber, but it's a killer top speed monster.
To bring up your RPMs, you need to open up the ports on your motor and balance your crankshaft. There's tons of information on porting available, and these china girl motors are pretty forgiving.
To bring up your RPMs, you need to open up the ports on your motor and balance your crankshaft. There's tons of information on porting available, and these china girl motors are pretty forgiving.
Jim: You need to port that motor, chances are it's not breathing well and it needs some tuning. A 41 tooth shouldn't be a serious drag on a 49cc.
