I bought a mutt mod sled this summer. 02 800 Motor, Gen II bulkhead, edge hood and belly pan, aftermarket tunnel, Holz rear suspension, lots of mods and tons of stuff put together totally wrong. I found after getting it home and tearing it down that it has 10 tooth Yamaha drivers with a 151 X 2 Polaris hill climb track. What would be the advantage of 10 tooth drivers, more surface area? Sled rides ok, little sluggish on the bottom end, thinking of gearing down a little. Does someone have a gear recomendation as I am sure the larger diameter sprockets will change the Polaris specs. Thanks for the help.

with a bigger lug track I would drop to the 8 or 9 tooth depending on tunnel clearance, that will also help with bottom end bog

<<<What would be the advantage of 10 tooth drivers, more surface area?>>>

That's what I'm thinking. Minimize racheting, letting you run the track looser? Would also be larger OD for the track to turn around, usefull for the same reason guys are installing the larger rear idlers. If they aren't creating a problem, I wouldn't change them.

Wouldnt the wind tunnel effect outdo any gains made by the larger drivers? With a 2" lug coming much closer to the tunnel as the big 'fan' drives snow and air to the front of the tunnel.
Run extrovert drivers and you can run your track real loose.

they use the bigger wheels because in theory bigger wheels do turn easier and go faster. but with a taller lug track that is not the case. it makes the track and tunnel a tighter fit so it actually robs power by the air being compressed in the tunnel. same with any powder that gets up there.

for your lug track go back to 9 tooth atleast. that will gear it down and make it roll better.

Thanks for the advice guys. I didn't take the wind tunnel effect into consideration when I first started contemplating a change. However, I went and measured the difference between my 03 rmk same track 9 tooth drivers and this sled with the 10 tooth drivers. The stock sled has 1" of clearance between the cooler and the lug tip. The 10 tooth has almost 2" of clearance!!! Still trying to figure out how they did that. I didn't measure the chain case to see what size it is but from what I can tell it hasn't been rolled. The sled is already geared low I got into my Polaris book it has a 2.38 ratio when a stock 151 should have a 1.95.

I like the idea of these bigger drivers, like Michahicks said, there should be less rolling resistance. There seems to be plenty of room for air and snow to vacate the tunnel.

So this is what I am thinking for a gearing solution, someone please correct me if I am wrong. The difference in the O.D. of the drivers is 0.5". That is a 10% difference in diameter. If I apply that to the stock ratio of 1.95 that gives a new ratio of 2.14. What do you think? And how does too low of a gear ratio, ex.) what I have now, effect performance?

Thanks again for the help.

The bigger diam. will make gearing higher, not lower.

I have had a few discussions about this and there are a few guys out there that are of the opinion that larger drivers are advantageous for top end. Theoretically the closer the shape of your track is to a circle the less rolling resistance there will be. The same rational applies for big wheel kits. Now I've always discussed this as it pertains to a 1" or 1-1/4" track. Does it really make a tangible difference?

I do know this, The '03 F7s have 10 tooth drivers. If I remember correctly you need to drop three teeth off the top sprocket for every added driver tooth to achieve the same gear ratio , i.e. 25/40 w/ 9 tooth = 22/40 w/ ten tooth, roughly.

Another thing, If your 10 tooth driver is giving you more clearance, could the track possibly be the same track but a different pitch ?

Thanks Dog700 this makes sense.
By my estimation bigger drivers would be the equivalent of putting bigger tires on your truck. You gain speed but loose power. If I apply the drop 3 teeth on the top gear or the 10% difference in size from the 9 to the 10 tooth. I get a ratio of about 2.28 these solutions seem to match pretty close.

The sled now has a 2.38 ratio. By my calculations this ratio is 4MPH slower at 8000RPM than the 2.28 ratio would be. Is this a problem? I ride AK. No trails, no speed, just deep snow.

Thanks for the advice. Look forward to more.