Gearing on 90

[kgmtech]

Was wondering what gearing everyone was running on the 90 cvt style quads for racing mx,right now I am using a 17T front and a 28T rear,but it seems like everytime I read a forum where someone says what sprockets they are using it is a higher gear ratio than this.

[kgmtech]

The motor is a 42 stroke by 52 bore , with a Billy Holt cylinder and head and my own clutch set-up.

[bulldogfallon]

What does Billy recomend? He must have built it with a certain power curve in mind..


On our 90s we 20T Rear (32t or 30T) Rear

[i-zapp]

gearing is absolutely track specific (as opposed to clutching). i gear our machines to run out of clutch on the longest straightaway, ie, they begin to over rev at the end of the straight. if it doesnt you're too tall and giving up holeshot power. if it overrevs too early (too short) youre limiting your top end. that's an arm's length type rule of thumb and not 100% gospel... for example if the track has a large percentage of low speed corners and one long straight you can sacrifice some top end by gearing a little shorter even though it falls off the power at the end of that one straight, etc...

[bulldogfallon]

Nice explanation!!


Easy to understand and implement

[mxdad423]

We run 19/28 with 18" rear tires and we run 10 or more differant tracks and this gearing seems to work on every track, seems to be a great all around gear.

[hotquads1]

we like 19/ 25 on a built 90, and 19/ 30 on stock 90 but some will depend on the driver and the thumb, tire size and trans gear ratio, and cvt ratio. I like to run as tall a gear as the engine will stand, if it is too much gear for the amount of power you have it will noticbly fall off in performance.
marc

[etondaddy]

I have found 19/28 with a built 90 to be the best all around setup.