Gearing a tard

Hey Guys,

I know this has been done to death, but my search didn't find "THE" answer I was looking for. I have the 17 inch rims, a typical tard set up. The engine is being built right now. Basically stock except for high comp piston. I ride with sport bikes so I'd like to have it geared for 100-110 miles per hour. ( don't see myself riding at that speed but I'd like to be able to go 90 miles/hr with out worrying about the engine going boom. I've been reading and the gearing was suggested a 15 45 but that still seems high. I do recall seeing someone saying 15/39 or 15/40 for strick roaad riding. I will NOT be dirt riding....

Last, and I might put up another post, where do I find proper jetting set ups? I have an edelbrock carb(I checked their site already no luck) fmf titanium slip on muffler, highflow filter, and the bike will have the high comp piston....

IS there anywhere I can look that will tell me what jetting and set up to go with, seeing the specific set up I have.

Thank you in advance.


Gearing calc:

With a 15t you cant run the factory case saver, but some aftermarket ones do fit.

As for jetting, each bike is different, each altitude is different, and there is no universal answer. Edelbrock for the R specs 15-12 clicks from full rich for a good range.

I'm running 15-42 on mine, and it's pretty much right for my riding.


I have 15/45 and mine is still revving hi at 90mph, I would guess 15/40 or 15/42, I would be going taller but my first gear low speed in tight trails would require too much clutching, I ride 50/50 on-off road, if I only road street I would have 15/40, since big thumpers don't really like to rev hi or need to.

I have 15/40 gearing, I also have pretty good power to push it. If you're running the 650R, this is a good setup, don't know if the L can push them. My bike still pulled pretty good above 85mph, but the loss at low speeds, 15 to 45mph, I don't like. If you're running in the 50-60mph range most of the time, and just want a short burst to 100+, I'd run 15/42. I lost my motor last week trying to keep up with the sportbikes, I wouldn't run it more than a mile or two over 100mph. I had two extended high speed runs, the first netted 119mph, and the second netted a fried lower rod bearing at 106mph!

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