another sprocket thread....math involved?

[Dabomb]

hey fellow miniriders,

i decided that having my bike sit on 4000rpm while doing 60km/h is a lil high so with the help of the one they call the BananaMan will attempt to drop that rpm and gain some more speed.

now as you read it sits on 60km/h at 4000 rpm.
can some tell me if these calculations are correct?

17/26 = 0.653
0.653 / 0.472 = 1.385
40km/h x 1.385 = 55.4km/h?

17/26 = 0.653 = 138.5% 15.2km/h gain
17:28 = 0.607 128.6% 11.44km/h gain
17:30 = 0.566 119.9% 7.96km/h gain
17:36 = 0.472 100.0% 0km/h gain (my ratio at the moment)

is this correct or can someone point me in a good direction?(dont recommend me to a website calculator done a few of them)

 

[foolsp33d]

might be helpful...
Gearing Commander: Motorcycle Gearing Ratio Sprocket RPM Speed Chain Calculator

sorry i HATE maths..I just go by what I know.. smaller back means more top speed, larger front more top speed, bigger rear better acceleration, smaller front, better acceleration... best I can do im sorry...

 

[Dabomb]

hmmm dont no how 2 use that program properly.

 

[rossetti]

wat yas think a 17f/36r would be like on a 140 ducar 12" rear. would top speed be better? soz for takin ova thread i just wanna go faster.

 

[Dabomb]

lol depending on ur 4th gear ratio you would just get over 100k's, ive had mine at 115 km/h with those sprockets.

 

[rossetti]

awk. well im happy with that haha. thanks bro.

 

[Dabomb]

anyone confirm this?

 

[Gawain]

Iv got a few very good excel based calculators, very handy, il post them up when im home in a few days.

 

[rossetti]

wats the smallest rear sprocket you can get for a pit bike??

 

[thump*140]

anyone confirm this?

yeah dabomb i can confirm this one... i have a lifan 140 with 12" rear... gearing is 17/36.... top speed is a tad over 120 (very fu@*ing scary i might add on a mini....)
mind you i'm running an IRK, 33mm pipe and 28mm carby... redline a bit over 9500rpm, and she was screaming.... but yeah, your quoted top speed is about right....

 

[thump*140]

oh and rosetti, if you run similar mods to what i've done to mine, and tune it right, it will still pull pretty hard... mine is quicker in a straight line than both my atomik blitz 2fiddy and the missuses xmoto xb31... (14 horsepower pulling a 60 kg bike as opposed to 19hp pulling 112kg bike with 90kg rider...power to weight ratio on the 140 is clearly in its' favour...)

 

[LTN16]

yeah dabomb i can confirm this one... i have a lifan 140 with 12" rear... gearing is 17/36.... top speed is a tad over 120 (very fu@*ing scary i might add on a mini....)
mind you i'm running an IRK, 33mm pipe and 28mm carby... redline a bit over 9500rpm, and she was screaming.... but yeah, your quoted top speed is about right....

Whats the acceleration like running 17/36 ? Do you lose to much ?

 

[Dabomb]

Whats the acceleration like running 17/36 ? Do you lose to much ?

nah you dont, well it depends on how much power you have, with my setup the gears dont last very long at all and the speed is more than decent!

 

[Dabomb]

Iv got a few very good excel based calculators, very handy, il post them up when im home in a few days.

ill be waiting for ur post!

 

[Dabomb]

wats the smallest rear sprocket you can get for a pit bike??

member names BananaMan makes custom sprockets, he's making me a 28 tooth rear!

 

[rossetti]

oh and rosetti, if you run similar mods to what i've done to mine, and tune it right, it will still pull pretty hard... mine is quicker in a straight line than both my atomik blitz 2fiddy and the missuses xmoto xb31... (14 horsepower pulling a 60 kg bike as opposed to 19hp pulling 112kg bike with 90kg rider...power to weight ratio on the 140 is clearly in its' favour...)

yeh i was lookin to get a few of those mods over the next couple months. how the hell did you get 14hp out of a 140?? lol wouldnt mind that myself. wel i found out its runnin a 16/43 set up wich im not to happy with and i had it doin prob 90km/h the other day with my mate beside me on his 110.

 

[rossetti]

member names BananaMan makes custom sprockets, he's making me a 28 tooth rear!

hahahaha might have to get one and try it out lol. wat kind of speeds do ya rekon that would reach??

 

[Dabomb]

im thinking 130-140km/h

 

[rossetti]

holy F*#k im gettin me one lol. haha saw you last night like around 7:00 ridin along the foreshore.

 

[Dabomb]

haha came through cardiff at 230am to warners bay on a sunday nite, absolutely none on the road!