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Discussion Starter · #1 ·
I'm trying to figure out how to get alittle more out of first. It's way to short to second. I'm having to shift at 9mph roughly. Would like it to be at least 12-15. Assuming sprockets but don't know if that's up or down teeth front or back or both. Would prefer top speed over acceleration since I'm on a 125cc
 

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Ghost in the machine
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Smaller rear sprocket will achieve what you desire. You could go with a larger front sprocket also but on many bikes the engine cases limit you to going up more than 1 tooth.
 

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Gone
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The rear sprocket is probably the easiest one to change, if you can find a compatible one. You may have to modify or remove the chain guard if it causes clearance issues.
 

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These other guys hit the nail on the head, change one of the sprockets. You can even improve top speed. But remember, where you gain in one place you'll likely lose in another.

Side note: The vendor for my Hellcat cancelled the order because no stock. That's cool, I'll probably just go vintage 125cc or 150cc anyway. ;)
 
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I guess we are supposed to just ASS YOU ME what kind of bike it is:surprise:

Sam:smile_big:
 

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OP has an Icebear PMZ125 :)

 

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Ace Tuner
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Your engine may not have enough HP to 'pull' very much of a gearing change.
I've found that the stock factory gearing is usually a pretty good compromise with an unmodified machine.

One tooth on the front sprocket makes a BIG difference.
I agree with ketchboy about starting with two less teeth on the rear... or maybe just one less ?
 

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One sprocket (usually the rear sprocket) will have an uneven number of teeth so that the tooth which engages the joining link on the chain moves around the sprocket. If the number of teeth on both sprockets are even then only certain teeth will engage the chain joining link and those teeth/tooth will wear unevenly.

Therefore to maintain an uneven number of teeth on the rear sprocket you should remove/add multiples of two teeth.
 

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Ace Tuner
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One sprocket (usually the rear sprocket) will have an uneven number of teeth so that the tooth which engages the joining link on the chain moves around the sprocket. If the number of teeth on both sprockets are even then only certain teeth will engage the chain joining link and those teeth/tooth will wear unevenly.

Therefore to maintain an uneven number of teeth on the rear sprocket you should remove/add multiples of two teeth.
Not understanding am I. ?

"tooth which engages the joining link"
"only certain teeth will engage the chain joining link and those teeth/tooth will wear unevenly."

I'm thinking 'joining link' is what I call the master link but..... Huh? (To everything else).
 

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Members of Chinese bike forums report changing the sprocket size does result in a higher top end speed or higher low end torque. Of course, if you go higher speed you are going to lose acceleration.
 
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Discussion Starter · #15 ·
Members of Chinese bike forums report changing the sprocket size does result in a higher top end speed or higher low end torque. Of course, if you go higher speed you are going to lose acceleration.
Btw Miss Mercedes I got a Mikuni 140cc carb and jets with Chimera intake and a mid pipe for my Akrapovic exhaust! Should be here within the next 3 weeks ? I'll do a video on my channel when installing. Still haven't put the Shinko white walls on yet either.
 

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Appericate it guys and gals. Will be going up a two teeth on rear and see how that guys. One tooth if any on front.
If you're trying for a higher top speed you would need to go down two teeth on the rear sprocket. (Smaller rear sprocket).
 

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Discussion Starter · #17 ·
Appericate it guys and gals. Will be going up a two teeth on rear and see how that guys. One tooth if any on front.
If you're trying for a higher top speed you would need to go down two teeth on the rear sprocket. (Smaller rear sprocket).
Ah, meant down. And what kind of loss in acceleration are we talking and gaining in too end? Cause main reason for this is to get a longer gap between each shift, primarily first. It's too short.
 

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Do searches on "bicycle gearing explained"

Hello:

It's very similar, front sprocket, rear sprocket, but a motorcycle has internal transmission gear ratios that also calculate into the final result. I searched for the title of a book I have on bicycle gearing, that has calculations on front and rear gearing and inches of travel, couldn't find it online. The smaller the front sprocket, the faster you will go, but for a motorcycle, there might also be engine load considerations, like overstressing the engine from a standing start trying to get higher top end. The items to consider would be the front sprocket size, the rear sprocket size, and the transmission gear ratios themselves. Hope this doesn't confuse you, but rather, offers you direction and food for thought on obtaining what you would like.
 

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You will probably have a longer stretch between shifting gears. The real issue is putting too much strain on the engine when starting out. I'm not sure how much with your small engine, though. It never really effected my honda 750 when I went one tooth bigger on the counter shaft and two teeth smaller on the drive.

If you do notice a big difference, just add a little more throttle, and slip the clutch. You DO know that you have to get a sprocket with the correct chain pitch, right?
 

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Discussion Starter · #20 ·
You will probably have a longer stretch between shifting gears. The real issue is putting too much strain on the engine when starting out. I'm not sure how much with your small engine, though. It never really effected my honda 750 when I went one tooth bigger on the counter shaft and two teeth smaller on the drive.

If you do notice a big difference, just add a little more throttle, and slip the clutch. You DO know that you have to get a sprocket with the correct chain pitch, right?
This is my first chain driven bike. I'm use to belts on my 50cc. So, no.. "chain pitch" is foreign to me
 
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