Indy 500 clutching & gearing

billybob479 · Jan 8, 2004

Hi all,

I have a stock 1990 indy 500. I am looking at tuning the clutch and gearing.

Currently it has 19/35 gears. The primary has a light blue spring with 10MB weights and a red spring with 36 degree helix in the secondary.

I ride in ditches and fields no groomed trails here!! I want good pull of the line without compromising top end too greatly.

Any suggestions or tips?

I am considering a thunder shift kit, to try different weight combinations, is this worth it?

xcr440 · Jan 8, 2004

silver spring 45-36 helix in secondary, 10MW weights leave spring alone.

billybob479 · Jan 9, 2004

What did you have for gearing?

Indy600X · Jan 9, 2004

Gearing is up to you. General rule of thumb for TOP sprocket: up in teeth=more top end speed, slower hole shot. Down in teeth=less top end, quicker hole shot. For BOTTOM sprocket: it's the exact opposite of top sprocket- more teeth, less top end...etc. I've heard the best gear ratios, for performance trail riding, are between 1.7 and 1.8. You are currently @ 1.84 with the 35/19, so not too bad. A higher gear ratio will have better low end compared to a lower ratio, which will have better top end compared to the lower. I dropped one tooth on my top sprocket and the sled did have a better hole shot, lost about 5 mph on top end.

xcr440 · Jan 9, 2004

stock gearing, you could drop 1 tooth on top if you want.

Indy 500 clutching & gearing

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