gearing

I'm currently building a 125cc 4 speed manual motor onto a bicycle but I'm unsure what sprocket sizes I should chose. I want to have a decent amount of top speed (80kmh should be easy with a 4 speed transmission) but still have acceleration around the city. Any help is appreciated.

So I am building a 125cc lifan bike, and I am trying to figure out what a good gear reduction would be. The engine itself has internal gear reduction, 4 speed. 1st gear is 2.833:1, 4th gear is 0.958:1. I was thinking about 12.5:1 gear reduction after that, which if my calculations are correct...

Have a HF 79cc going on a bike with 26" tires. Engine will be keeping the governor so 3600-4000rmp (gov tweek if I can figure that out). Thinking of running a jackshaft with 11 tooth clutch, 22 tooth input, 9 tooth output, to a 48 tooth rear. If I figured right should be a 10.67 final. Will...

So I was thinking it might be possible to convert my bike from having 2 gears in the front over to just one gear, then I could steal the front derailleur, modify it, and put it onto the motor chain and add a 46t sprocket next to my 36t on the rear hub, then fashion some sort of spring loaded...

hi i'm looking for some info on a two stroke china 49cc motor kit LEB off ebay. The kit came with a 39 tooth sprocket and i have it mounted on a 10 speed road bike it had 27" tires i changed the to 24". I'M wondering if its geared to hi, it doesent's have any hill climbing power the top...

Hey everyone, I'm looking to put a new sprocket on my bike, either a 36 or a 40 tooth. I'm a little hesitant to jump striaght to the 36 tooth from the 44 tooth because I live at 7200 ft and I still have to climb a few hills on a daily basis...Recommendations?? Anyways, let me know if you are...

I am trying to use the gear calculator from the other forum but I dont think it is working out for what I need it to do.. I am wanted to do a 3 way jackshaft.. Honda gx50 (11t) drives a fixed sprocket on one side (22t) then the other side of the jackshaft a chainring (40T) and a...