Chain and sprocket combo questions.

[barncat]

I noticed today my front sprocket is Shot. I'll assume I have the factory 13/38. I'm looking to maybe increase my top-end a hair. Will going to 14/40 improve it enough to be worth any jetting headaches?
I'm already jetted for the pipe, and I still need to do an airbox mod.
Am I better of keeping what's in it?

I have re-geared on my street bike, with noticeable difference. Will I be ok going 14/40 without a re-jet.

As far as Airfilter I'm considering the Uni-filter setup.

 

[duneracerweston]

You won't haveto rejet if you change gearing but you will have to change it for the pipe

 

[barncat]

I'm cool on the jetting.

Let's say I want to go a different route and do a 12/40 setup, How much of my topend will I loose?

I do mostly trail riding, and rarely open it wide up. Would I be better off strengthening my lower end, than try to achieve top speed(which will be a marginal gain at best)?

 

[deerman2701]

EDIT:

take a look here

http://www.yfm350.com/forums/showthread.php?t=20782&highlight=gearing

 

[duneracerweston]

Every tooth you change you loose/gain 5-8 mph I personly like the 14 38 but I run mx and have a supper mod motor so for the 12 40 set up you wind out the gears really quickly if you are looking for more pulling like a tractor 1240 will work but if you are running fast normal trails I would run the 1440 IMO

 

[barncat]

Cool, thanks! My SearchFu sucks. I typed everything except Gearing.
I'll look at my tires and go from there.

 

[deerman2701]

dont mean to thread jack, but.

what are you guys thoughts on 22 inch rears with a 14 front and stock rear sprocket? i want to have speed but i need bottom end torque for these tight trails. i need speed cause we do road riding and if i get into a chase by a cop i need SPEED!

im debating on keeping the current 20's on the rear or getting new 22's...

 

[hawkster0001]

wait, so do you have 20 or 22 inch tires? i have 20's on mine and with stock bore 14-40 and that tire size is about right for the warrior

 

[barncat]

I just went and checked. I have 21" tires (21x12x8) So I'm thinking of running 14/38.

Any other recommendations, I'm all ears. I'm not sure what size the paddles I'm running are, but I'll burn that bridge in May.

 

[DeadLastRacing]

13/40 is stock gearing.

 

[baddawg]

Got this off the site somewhere;

13/40 and 22s is 7.16 ratio, Stock gearing and 62 MPH.
12/40 and 22s is 6.60 ratio, Motor will be very torquey but lose top end.
12/40 and 20s is 6.00 ratio, First gear will be useless, and you'll run though the gears way to fast.
13/40 and 20s is 6.51 ratio, Same as 12/40 and 22s.
13/39 and 20s is 6.66 ratio, almost same as above.
14/40 and 20s is 7.01 ratio, Better but not close enough to stock.
14/38 and 20s is 7.38 ratio, pretty good all around ratio.
14/39 and 20s is 7.19 ratio, Almost perfect to stock gearing.
15/40 and 22s is 8.27 ratio, getting way out of the warriors torque range
15/40 and 20s is 7.51 ratio, Too high for stock motor will be sluggish.
15/38 and 20s is 7.90 ratio, Good for a 446 motor top speed over 80.
16/40 and 20s is 8.00 ratio Good combo for stroker motor.
13/40 and 18s is 5.86 ratio, Top speed will be like 40 MPH screeming.
14/40 and 18s is 6.31 ratio, Same as 12/40 with 20s.
14/38 and 18s is 6.47 ratio, Same as above.
15/38 and 18s is 7.11 ratio, Almost perfect to stock gearing.
16/38 and 18s is 7.59 ratio, Good if your motor can handle it, top speed will be in the mid 70s.

 

[deerman2701]

well got my old chewed up sprockets and replaced em with 14/40 with 20's and i do like the setup!

my old back sprocket had 41 teeth ?? i never knew they made 41. oh well!

 

[barncat]

I just decided to run with the Stock 13/40 setup. With 21" tires I'll keep my torque where it's at. I haven't even checked to see where I'm at now, but as chewed up as the F.S. is, anything will be an improvement!

 

[MotoArts]

Got this off the site somewhere;

13/40 and 22s is 7.16 ratio, Stock gearing and 62 MPH.
12/40 and 22s is 6.60 ratio, Motor will be very torquey but lose top end.

At least these first 2 are wrong. Don't know how they factored in the tire height, but the "ratios" are bass ackwards.

40/12=3.07 gear ratio
40/13=3.33
(Tire height not being considered, since both figures in the chart are using the same height anyhow.)

The descriptions are correct though. "Deeper" ratio (higher #) means less top end but better torque multiplication.

 

[barncat]

Because I need to know, does anybody have the formula handy, for figuring out the ratio?

 

[MotoArts]

Because I need to know, does anybody have the formula handy, for figuring out the ratio?

Rear teeth divided by the front teeth = final drive ratio

 

[barncat]

How does your rear tires figure into it then?

 

[barncat]

it looks like front divided by rear, multiplied by tire height, OR
Tire height divided by rear sprocket multiplied by front sprocket, is how the drive ratio is figured. On my setup it is equal to 6.9 (13/40x21).

Doing the math that way, all the ratios in the chart are accurate

 

[baddawg]

At least these first 2 are wrong. Don't know how they factored in the tire height, but the "ratios" are bass ackwards.

40/12=3.07 gear ratio
40/13=3.33
(Tire height not being considered, since both figures in the chart are using the same height anyhow.)

The descriptions are correct though. "Deeper" ratio (higher #) means less top end but better torque multiplication.

Tire height is included in the ratio so it has to be considered :iagree:

 

[MotoArts]

Yes, but what i'm saying is if the tire height stays the same, but final GEAR ratio changes (lets say reduce the front sprocket tooth count only), the ratio will get larger (bigger #), not smaller like the chart shows.

I still don't know how to figure how the chart comes up with a "ratio" by using rear tire height.
I ain't too good at that there math thing.

This is interesting though:
http://www.fullsizechevy.com/forum/...01-tire-size-reduction-final-drive-ratio.html

This one is pretty flexible with plugging in figures:
http://www.csgnetwork.com/multirpmtirecalc.html