Sprocket Sizes

[twowheeledfox]

My bike, with 26" wheels and the stock 10t/44t sprocket setup will do 30mph+ but revs too high for my comfort at that speed. On a WOT run today, 30 seconds flat out I hit around 34-35mph but with the motor at very high revs. I would like to cruise at 25-30mph more comfortabley.

I know sprocket downsizing creates a torque issue. I have the 68.5cc slanthead, stock carby and pipe, but it has noticeably more compression (and torque) than the other 50cc flat I had. It pulls me (160lbs) and itself plus tools and spare fuel (125lbs) with just a push from a dead stop. Would it be capable of handling a 40t, 38t or even 36t? What speeds could I expect below 6000rpm (my max cruising speed)? How well or poorly would it handle moving from a stop? What is an fairly easy way to get more torque to help with stops and acceleration (or should that amount be enough?).

Or alternatively, I have heard Bikeguyjoe and Cabinfever talk about getting to 38 or so with the stock 44t setup, what does the motor sound like on those bikes at speeds of 25-30?

 

[taddthewadd]

I have a 38T. I weigh 160 also. It doesn't have enough torque. Its like it only wants to go fast. It really struggles going from take off to mid rpm range. I think its great if you are going long distance and wanting to go at a good pace with the rpm's not too high but if you are putting around a neighborhood or doing a lot of stop and go you will be disapointed. Another factor is my engine isn't broken in yet, maybe once it is broken in it will have enough power to pull that 38T. If it doesn't I think I will stick with the 44T.

 

[mapbike]

I have a 41T on my bike with 66cc engine, I am 200lbs and its on a bike with suspension front forks and a few other things that add maybe 15-20lbs to the weight of the bike which is fairly heavy being that it is an American made frame that is thicker than the China frames, I can cruise @28-30 with the rpm's at a managable level, it will go 38MPH WOT topped out but revs are through the roof and not at all comfortable, I have many fairly good hills out where I live and it pulls me up the hills pretty good, I usually hit the top of them still running @ 23-25 MPH if I hit the throttle hard 20-30 yards before I start up the hill, I'm thinking of trying a 36T I have just to see how it will pull me so that I can cruise @ 30-32 with less revs but I may have to pedal a little at the top of the hills at times, I will find out when I make the switch in a month or so.

My point here is that I really like the 41T over the 44T myself I have ran both and the 41T is a good all around gearing in my opinion.

 

[Cabinfever1977]

I have a 44t and weigh 125lbs and can hit around 32mph WOT. I have my engine and bike mounted in a way that there are almost no vibrations. But at WOT it sounds like im riding a timebomb with hundreds of bees(kinda like a angry dirtbike). I can take off without peddaling and can even pop a wheely if needed. Most of my rides are 1 mile to a store and 1 mile back. I can go up hills without peddaling also.

If you will be riding longer distances and want lower rpms, try a 41t or smaller but you will sacrifice some torque and may need to peddal to get going. If you just ride around the block or short distances the 44t works fine.

 

[Salty Gator]

I have a 44t and weigh 125lbs and can hit around 32mph WOT. I have my engine and bike mounted in a way that there are almost no vibrations. But at WOT it sounds like im riding a timebomb with hundreds of bees(kinda like a angry dirtbike). I can take off without peddaling and can even pop a wheely if needed. Most of my rides are 1 mile to a store and 1 mile back. I can go up hills without peddaling also.

If you will be riding longer distances and want lower rpms, try a 41t or smaller but you will sacrifice some torque and may need to peddal to get going. If you just ride around the block or short distances the 44t works fine.

I use one of Jim's 38ers and adapter....as well as his new motor mounts and straight shot intake.... I weigh 190 #'s.....all I have to do is pedal a couple times and kick it in...it takes off....it whistles up to around 18 MPH then it's like a turbo kicks in.....my computer tells me I've had it up to 34.5 MPH ....flat road... ( recently repaved )....I've used a 44 tooth on previous builds and they never even made it to 28 MPH.....and the motor sounded like a pissed off chain saw or an incoming RPG....if you don't have any steep graded hills to climb I'd go with a 38......you can cruise comfortably at 25 and the engine is barely above idle.....this also allows you to get a heck of a lot better mileage than a 44....hope this helps....


Laters,
Salty

 

[Cabinfever1977]

I just got mine up to 33.2mph today and it wanted to do more but i let off the throttle, im guessing it was because its warmer outdside and i turned the idle up a little. My mileage is 180+mpg with the 44t. But i would still like a smaller sprocket for lower rpms and would think with my weight that i still wont have to peddal to take off.