rear spockets?

[PIMP50]

ok fellas, i hav a 39tooth rear sproket on my pitster is got a yx150 with a v2, oko 28 mm carby and a 15 tooth front sproket and the gear ratio is way way to short, should it get a 37 tooth rear sproket or 35 tooth? or get a 17 tooth front sproket ? cheers guys

 

[sean01]

id be changing the front as it easier and probly cheaper, but either way you may need a new/longer chain

 

[dadof2]

i believe one tooth in the front is equal to 2 teeth in the back
if im wrong im sure someone will correct me
and all the info ive found goes with what sean is saying change the front cog first

 

[motorman]

i believe one tooth in the front is equal to 2 teeth in the back
if im wrong im sure someone will correct me
and all the info ive found goes with what sean is saying change the front cog first

Close mate but I think it's actually 3 teeth on the back (well close enough).

 

[dadof2]

Close mate but I think it's actually 3 teeth on the back (well close enough).

he he he cheers:grinning-smiley-003

 

[MiniFighter]

i believe one tooth in the front is equal to 2 teeth in the back
if im wrong im sure someone will correct me
and all the info ive found goes with what sean is saying change the front cog first

I think im with Dad on this one?

 

[Barnesd09]

Pimp.. What kind of riding are you going to be doing? how ofen do you really tap it out in 4th?
With a YX 15/39 420 pitch and 12" rear, you would be looking at about 90km/h tapped, a V2 will let the engine rev harder so you would be approaching 95 - 100. each front sproket is good for about 10 km/h extra.
So a 17 tooth front would see you tapped at about 110.
I race with a 15/41 combo and find that is sufficient as I find I'm never on the limiter in 4th for more than a second in most cases, dirt or motard.
TRail riding would be different and I'd be going taller gearing to look after the bike as there is no point in reving its guts out for a couple of hours for the sake of pulling power wheelies.
If you on fire trails or easy dirt roads, then I'd be inclinge to go a 17/39 or a 16/37 set-up and that way you wont have to change chains, just adjust the tension, or even a 17/35 like the Rx's run (I think) .
But with the taller gearing, you will have to ride the clutch a touch more when taking off.

 

[PIMP50]

cheers guys for the info im kind of into ramps and open mx tracks and trails

 

[sean01]

yeah one thing to consider also, is by upping the top speed your stealing from the bottom and this has greater impact on your gearbox and clutch.

a lot of people are reporting rubbery type crap coming out of the engines on an oil change.
i believe this is actually parts of the clutch.. could be fiber from the plates and also bits of rubber from the cush drive rubbers..

so depending on your where your riding id maybe consider a larger cam and get heavier valve springs to widen your rev range (sounds like you give this engine a hard time)... maybe even just the springs would be enough..
also hd clutch springs wouldnt hurt

playing with your cam timing can help to..advance for less top end and retard for more.(but not many ppl to do this)

 

[rumble]

Ive just put a 16/37 combo on my yx150. Gives a noticeable increase in gearing. I have got a 17 tooth front but havent tried it yet. Got a feeling it would put alot of strain on the clutch.

 

[PIMP50]

i also hav kevlar clutch plates and HD springs if that even matters