sprockets and speeds?

newbybikelover

New Member
Apr 8, 2012
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abilene texas
What would be faster in over all speed, not acceleration, a smaller sprocket? or a bigger sprocket? im looking for a little more speed, right now im at the 44T sprocket that came with my engine
xct2
 

newbybikelover

New Member
Apr 8, 2012
11
0
0
abilene texas
would the 3 teeth difference be alot from where im at now? or would it be even faster for a 36T sprocket to be installed. im only pulling about 15 mph if im lucky because i messed up part of my engine/carburetor and had to get a replacement, now i just got my new RT thatsdax carb and havent riddin it yet, but i would like to reach around 25-30 mph.

i put on the .70 jet the carb came with, but im prob going to see if i can order somethign inbetween .65 and .70 if not ill have to drill one out.
 
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Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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Depends....you can over gear if you are too heavy, have big hills or lots of wind. 41T seems to be the best compromise.

You SHOULD get better tyhan 15 mph with a 44T....something is wrong if you don't.
 

rustycase

Gutter Rider
May 26, 2011
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It is most likely you will need to go through the plug reading/jet adjustment routine with ANY carb on an ht.

Best to review the threads on that subject.

Every chinagirl should be able to do 25-thirty mph on level ground.
rc
 

dragray

New Member
Mar 10, 2012
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Indiana
first of all, what size wheels does your bike have on it?
if you have 26" wheels and you are running a 44 tooth sprocket, you should be getting close to 30 mph top speeds with that set up.
if you drop to a 41 tooth you will see a TINY increase in top speed, but not very much.
if you drop to a 36 tooth sprocket, you will gain quite a bit of top speed, but you will lose a ton of bottom end torque for take off.
a smaller rear sprocket gives you more top speed, less low end torque and a lower crusing rpm .
a bigger rear sprocket will give you less top speed, more low end torque and a higher cruising rpm.
now, tire size has something to do with this as well because if you have a 26 inch rim with a 27 inch tall tire, it won't have as much top speed as if you had a 26 inch tall wheel with a 30 inch tall tire (for example).
the smaller the rear wheel and tire, the less top speed you will get.
for example, one of my bikes has a 20" rim with a 22" tall rear tire and a 41 tooth sprocket. my top speed is around 25 mph.
my other bike has a 20" wheel with a 24" tall rear tire, and a 41 tooth sprocket. top speed on that bike is around 32 mph.
both bikes have modified exhausts, re-jetted and tuned carbs, and they both weigh about the same.
sprocket size, wheel diamter and tire diameter all have a lot do do with the final gear ratio. you can change the gear ratio simply by putting on a taller or shorter back wheel and tire.
but always remember, a smaller rear sprocket will give you more top speed, lower crusing rpms, but you will lose bottom end torque. basically, it will take longer for you to get up to cruising speed and to top speed.
a bigger rear sprocket will give you more low end torque, but less top speed. you're bike will get up to cruising speed and top speed quicker (but your top speed will not be as fast as if you had a smaller sprocket.)
gear ratio numbers are backwards that what you would think. A higher number is actually a lower ratio, and a lower number is actually a higher ratio.

for example, lets say that we have a muscle car with a stock v-8 and we play with the gear ratio a little. lets assume that we change nothing on the car except for the gear ratio in the differential and we start with 4:88:1 gearing. this gearing would be low and good for quick acceleration used on the drag strip, gas mileage will suffer, the engine will be revving higher, and top speed will go down.
lets assume that this car will run the 1/4 mile with this gearing at 13.0 seconds at 90 mph (a 4:88:1 ring gear is physically bigger around than a 3:08:1 ring gear)
now lets take that same car and put3:08:1 gearing in it. This gearing is high, acceleration won't be as quick, gas mielage will go up, the engine rpms will be low, top speed will go up.
so now this car may run the 1/4 mile in 17.0 seconds, but the top speed may go up to 95mph.

with a lower gear (bigger physically) the car will accelerate faster and got to the end of the track in less time than if it has the higher 3:08:1 (smaller physically) gear. but the smaller gear gives you more top speed and less quickness on acceleration.
 

bikeman8

New Member
Mar 12, 2012
18
1
0
ofallon mo
i have a few questions about speed.

first off, i have a mega motors 66cc engine kit from bike berry .com

it is all stock.

44 tooth came with it.

im putting it on a new bike with a flipflop hub and im going to use the 18 tooth sprocket on the wheel for the motor.

it has a 9 on the engine.

i weigh about 225 and am 6 feet tall, i can peddle up to 28 by myself, so start ing it is not a problem i only use the motor when i want to go fast, so i want speed, anything slower than 20 i peddle.

does anyone know about how fast ill go?

the wheel size is 26 inches.
 
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Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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These little HT engines don't have enough power to to push a bike down the road with a 18T sprocket; (especially with a heavy rider). :(
Bairdco can get away with running a 28T because he only weighs 130 lbs & he has a super frankenstein hot rod engine. (Yes, his bike is crazy stoooopid fast).

I use 40T sprockets on all my personal bikes & I weight 210 lbs... I'm considering trying a 38 or 36T on my current bike because I have done a lot of mods to it & I think it might be able to pull me with the higher gearing.
 
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wayne z

Active Member
Dec 5, 2010
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I agree with Venice. quite tall gearing.
If you use an 18 t, you'll be pedaling all the time to help the motor, but maybe that will work for you.
 

bikeman8

New Member
Mar 12, 2012
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ofallon mo
i ususally peddle with it any way, but i can ride from a flat stop just like a motorcycle, it has about 20 hp since i put a new pipe on it.

i get up to about 35 fom a stop only motor power in about 20 seonds

i know it has the power to do it, i just wanted to know how fast it would go
 

robbomberbomyea

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Dec 10, 2011
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i ususally peddle with it any way, but i can ride from a flat stop just like a motorcycle, it has about 20 hp since i put a new pipe on it.

i get up to about 35 fom a stop only motor power in about 20 seonds

i know it has the power to do it, i just wanted to know how fast it would go
get a spedometer,then youll know for sure, im maxed out at 32mph with 44t on sgt. scruffy.lucky to see 25 with 36t on the occ,but no speedo on that bike so cant say for sure. laff
 

dragray

New Member
Mar 10, 2012
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Indiana
i ususally peddle with it any way, but i can ride from a flat stop just like a motorcycle, it has about 20 hp since i put a new pipe on it.

i get up to about 35 fom a stop only motor power in about 20 seonds

i know it has the power to do it, i just wanted to know how fast it would go
wow. you're gtting 20 hp out of a stock h.t. engine with a pipe on it? :)
I ride mine like a motorcycle all the time, and i never pedal.

again, an 18 tooth rear sprocket won't work. you'd have to get the bike up to 40-45 mph before the engine would even begin to pull it....good luck with that.
 

dragray

New Member
Mar 10, 2012
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get a spedometer,then youll know for sure, im maxed out at 32mph with 44t on sgt. scruffy.lucky to see 25 with 36t on the occ,but no speedo on that bike so cant say for sure. laff


I disagree, because my o.c.c. has a 41 tooth and i can get right about 32 mph out of it.(verified with a radar gun) my engine is internally stock, with a tuned nt carb, high flow air filter and a custom made free flowing exhaust(not an expansion chamber, not a straight pipe.).
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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I disagree, because my o.c.c. has a 41 tooth and i can get right about 32 mph out of it.(verified with a radar gun) my engine is internally stock, with a tuned nt carb, high flow air filter and a custom made free flowing exhaust(not an expansion chamber, not a straight pipe.).
I would try a 36T on a OCC (because it has such a small rear wheel).

I use 40T sprockets on all my 26" wheel bikes.
 

robbomberbomyea

New Member
Dec 10, 2011
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toledo oh
I disagree, because my o.c.c. has a 41 tooth and i can get right about 32 mph out of it.(verified with a radar gun) my engine is internally stock, with a tuned nt carb, high flow air filter and a custom made free flowing exhaust(not an expansion chamber, not a straight pipe.).
maybe im going faster? never radar checked,no speedo,never held wot,just breaking in ,running starfire gt2 ho,custom pipe,nt carb etc
 

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Jroge1523

New Member
Aug 28, 2017
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Ok here is my opinion i wanted to go faster too so i ordered a 38 toothe sprocket no speed increase at all top speed 37 mph with 44 toothe and 38. The only thing i noticed was when i got up to those speeds the engine didnt sound like it was going to blow up which is great and it got up to that speed faster hardly change on take off and hills. So i went down to a 36 toothe well top speed 37mph i weigh 175. My tires are 26×2.0 i dont know if that matters. Yes i would recommend 36 toothe sprocket im about to go to 32 i have 2 bikes
 

Jroge1523

New Member
Aug 28, 2017
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My goal is to hit 40 i have ported my engine got a cnc intake drilled hole in airfilter cap upgraded the wire from the cdi so i dont have to remove sparkplug cap and got a ngk bphs7 sparkplug 36 toothe sprocket standard muffler mods and after all that top speed 37mph lol. Im about to get a high compression head and a performance muffler
 

Chaz

Well-Known Member
Jun 3, 2012
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Vancouver, British Columbia
Welcome to the forum, J, if you get a high compression head and an expansion chamber you will likely hit your target. I'm guessing that's what you mean by performance muffler. Those two items are on my list as well. The Fred head from crmachine.com is highly regarded. For the expansion chamber I would suggest you do some research in this forum for more info and opinions.