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Discussion Starter · #1 ·
Not sure how this works im new and i dont understand all the information that has been given to me. wish they made it simpler maybe a book for dummies haha well i just want my bike to be able to cruise at 55 mph without having it at such high rpm's in 5th gear. i have a 1974 ts185. any help is appreciated. thanks!
 

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If you increase the number of teeth on the front sprocket, or decrease on the rear sprocket, the rear wheel will turn faster at a given engine rpm. You will also reduce the acceleration rate by a similar amount. Example: your current front sprocket is 15T and your current rear is 45T, so your rear wheel will turn once for every three rotations of the front sprocket. Change the front to 17T and the rear to 43T and the rear wheel will turn once for every 2.5 turns of the front. The net effect is the engine rpm will be reduced by ~16% at any given speed (2.5/3 = .84).
 

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Discussion Starter · #3 ·
Thanks! You made it much easier to understand then all these other sites ive been to. i have another question i am at a 39 tooth back sprocket right now i am not sure what the front one is as there is a stripped bolt on the part i need to take off to get to it. but seeing how i already have a 39 tooth, my front sprocket is probably a fairly small sized sprocket correct? so if i were to go one or two more teeth on the front it should level out my bikes rpms good enough for street riding by say 10 mph faster at lower rpms? That is what my plan is at the moment to switch out the front to a bigger one if that doesnt work ill go ahead and buy a bigger back sprocket since im at 39 teeth right now and if that doesnt work ill buy a smaller back sprocket and just mess around with the different sizes and try to get a refund on what parts i dont need in the end haha. thanks for your help and lemme know if what im doing is the right thing to do. i hate waiting for parts in the mail grrrrr
 

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Discussion Starter · #4 ·
i just counted the front there are 12 on the front sprocket. my bike is a 185 suzuki 5 speed. should i put 13 or 14 teeth sprocket in there? it is pretty low gearing right now. i can cruise comfortably at 30-35 mph in fifth gear without the rpm's too high. i hope the sprocket change fixes this..
 

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Changing from 12 to 13 teeth would change the final ratio from 3.25 to 3, so your rpm would drop about 8%. IOW, instead of 4000 rpm at some mph, it would then be about 3700. Going up to 14 teeth would reduce the rpm by about 14%, so the rpm would then be just over 3400. Be aware that you may need a chain with another full link, and make sure there is clearance for a larger front sprocket.

That bike has a redline of 8000 rpm, right? So, how high are the rpm at 35mph? You're probably below the power curve at those speeds in fifth. With a redline of 8000 rpm, then 4000-5000 would be a good cruising rpm. If that's too high, then you need to get accustomed to higher rpm, or a bike that doesn't rev that high. My VS800 (redline 8500) turns at 3800 rpm at 55mph, and my CB450 (9000+) is about 4400. Not high at all, IMO.
 

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ya its a simple math formula. but most make it more complicated. it is the first result off of google.
****ing stupid.....

google this.

formula motorcyle gear ratio chart
 

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Its also probably worth mentioning that chains and sprockets can come in different pitches. Pitch refers to the distance between the pins of the chain. If using aftermarket sprockets and chains, look to see for numbers stamped on them or check that the pitch is the same before buying.
 
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