Indy 500 Gearing

[Goinboardin]

I'm on a 1990 Indy 500 with 136" x 1.75" running between 9000 and 12000 ft currently with 19/39 for gears. The calculated top end speed (80 mph @ 7800 rpm) is way faster than I ever go/would want to go as I'm usually climbing or in the trees. I was wondering what you all suggest for gearing; my track speed seems to fall off pretty quick (I know its just a little 500...so of course it does).

Am I likely getting all that I can out of her or could a ratio around 2.3-2.4 really help me out? I have a 64 and 66 pitch chain, so ratio's that utilize those would help. The chaincase is actually off a 95 XCR 600 (I liked the design much more). Are there any serious drawbacks to a 16 or 17 tooth top gear?

 

[manowar]

Yea smaller than 19 on top is hard on chains. I will have to do some checking on what can go on the bottom in that case . But on that thing 19/43 all the way if it fits uther wise 18/41 should fit if the 43 wont go in the bottom.

 

[chadkrump]

what he said, when u go smaller than a 19 or 18 on the top is really puts a hurt on chains... if anything change ur bottom.

80 MPH isnt bad for track speed. I really wouldnt want anything below 70 mph IMO but thats just me... sometimes u need that track speed to help ya out, good luck

CK

 

[Goinboardin]

Thanks

I thougt that might be the case with the smaller top gears. The manual I have for 96/97 polaris' has a table of gear ratios and doesn't list anything larger than a 41, so I suspect that is the largest that will fit. When I try out a new ratio I'll provide an update as to what kind of difference I get...could be a little while though, school is time consuming.

 

[volcano buster]

You will likely find that there aren't many gears made for that sled. I have a '93 440 that I put a 133.5 x 1.5 track under and geared down to a 18/41 I think. I had the chain so that part was easy, but I had to go through a guy that used to work for an AC dealer as the gear swaps were interchangeable. Make sure you are matching like chain styles and that you know the axle spline count and the chain width. You might get lucky and find what you need, but they are getting harder to find.

 

[skis_n_skid]

They are sprockets, not gears. Sprockets drive chains, gears mesh with/drive other gears.

You will likely find that there aren't many gears made for that sled.

He said he had a chain case from a 95 XCR 600. Shouldn't be any problem finding a variety of sprocket sizes for it.

 

[FEZ]

I would go to 18-41. This is what I run in my 700/144 for 6-9K

Keep in mind you can now pull more helix with the increased mechanical advantage of the gearing. A Polaris 40-36 is an excellent choice for your machine.