Best Sprocket combo for Mid Size bike

[truonga]

Hey just wondering what is the best sprocket combination for a mid size bike with a 14 inch rear wheel for good speed and acceleration but more speed
right now i am running 15-48 gearing .
Any ideas?

 

[Panda_ET]

what engine?

 

[truonga]

lifan 140cc

 

[crazzy #1]

whats wrong with the standard gearing not enough bottom end, not enough top end? what do you want out off the bike... whole lot of variables to concider! how you ride, where you ride! best to play with different ratio's to find the one that best suits you and your engines power output!

 

[kyunt]

he said himself he wants more top end speed!!! GGEESH

 

[Flarry]

48 rear is huuuuge, for 4speed chinas like yours I'd allways use 14/37, I think thats perfect.

 

[I_THUMP]

48 is far too big. Try a 37, 39 or even a 41 tooth. The smaller you go on the rear the more top end speed you will gain.

 

[numroe]

You wrote that you have a 14" rear wheel. Which with a 90/100 tyre, is nearly 3" larger diam than 12". You have 15:48 at present. So 15:41 with the same countershaft speed will be much taller/faster at the rear wheel. Your bike will be 14.6% faster actually. That's a huge change.

The rotational speed of each sprocket is inversely proportional to the number of teeth on it (circumference). You want the rear to spin faster, so the rear sprocket has to get smaller and/or the front one larger. Decide as a ratio how much faster you want to go. Say you use a 16 (+1) front, then you'll go 1/15th faster than before. Or if you use a 44 rear (-4) then you'll go 4/48 = 1/12th faster. -5 on the rear means 10.5% faster.

If you have a 12" rear and a Lifan engine, then something around 15:39 is very normal.

 

[truonga]

thanks i'm thinking of putting a 37 on the back then i'll have 15-37 gearing but then i might lose quite alot of power

 

[numroe]

So you got a 12" or 14" rear wheel?

15:37 with a 12 will be friggin quick wound out on 4th for a mid sized mini on anything but flat dirt. With a 14" rear it'll be useless. Way too tall for dirt riding.

15:37 is slightly taller than 16:39. I switch between 16:39 and 15:39 depending on how I feel about the track and gear choice for various corners.

Torque to the rear wheel will also depend on what gear your engine is in. The real problem is that your gears will be mega spaced out.

 

[truonga]

I'm not sure if I should go for a 37 now, but I might try it out and see if I like it or not.

 

[FiddyBasher]

I am having problems with my bigfoot in that first gear revs out really high but when you change to second the engine dies in the arse. Its kind of as if it has heaps of midrange but no low or high. Any ideas? Would this be more a gearbox gearing issue or a sprocket combo issue?

 

[Panda_ET]

more of acgearbox issue, 1st is very short its like the lifan 140 all up gearing its designed to get u off the line real fast, personally i found it painful I was having similar issues to u just not stalling. I went from the 15-41 stock to a 16-41 but havent tried a trail yet just track riding..it went really well but wont know till i hit a big hill i spose

 

[FiddyBasher]

By "dies in the arse" i dont mean stall (although it does that too but i blame the inner rotor kit/tiny flywheel for that)i mean it has no power til you hit kinda 1/3 revs....

 

[truonga]

i rounded 2 of the bolts holding the rear sprocket on, they are so tight that they don't even move. I've tried using lock pliers to get them off but no luck. Can anyone please help?

 

[Kingers]

tried an easy out?? they work pretty good try bunnings or any store like that, cost about 10 bucks

also panda hows your gearing go with the 16 on the front

I got a bigfoot and went out bush and it needs a bit mor speed currently its running 15-41 so i was thinkin of changin it to 16-37 would that be alright or would i loose alot of power?

 

[liljohn_92]

are they actaul bolts or allen key bolts?

 

[Kingers]

mine were alan key, i thought they all were alan key? but yeah they are tight i had to use a hammer to persuade them to come out

 

[truonga]

actual bolts (10mm) Havent tried easy out yet but I'll try find some later, do you find the easyouts in the drill section off shops?

 

[truonga]

I found these on ebay, 5PC Broken Screw Extractor Set Easy Outs Stud Remover - eBay Other Power Tools, Power Tools, Tools, Home. (end time 17-Oct-08 10:48:32 AEST) are they any good and will they fit 10mm bolts?