Gear Ratios

[TwoJugs]

I am looking to try some different gear ratios for 1/8 mile drags. I want to gear it down for better hole shot and use more gears. I see 13 - 14 - -15 - tooth motor sprockets for sale. I have a few wheel sprockets on the shelves too. Any rules on changing motor sprockets, minimum sizes? Advantages to uping the wheel sprocket instead. I know the bike now had an 18 tooth drive gear. It just about hits the case cover support and clutch rod. It was running 1/4 miles. Most bikes I see only use 3 gears in the 1/8. Being a smaller motor then most I am looking to use more gears to help the run. Anyone played around witrh gearing?

 

[pamcopete]

TwoJugs,

Here is an Excel spreadsheet that shows RPM vs MPH for all combinations of gears, sprockets and tires.

XS650 Revs and Gears

Click on the yellow cells to reveal pull downs to select your values.

 

[TwoJugs]

Nice info Pete. Thanks. Took a while to figure out what I was looking at but very useful once I got it down. Too bad the pinion values didn't go lower for my ap. I see smaller front gears available and I think a swap there might be easier to do than change rear sprockets while testing and tuning.

 

[pamcopete]

TwoJugs,

OK. I added 13, 14 and 15 to the front sprocket pull down.

 

[TwoJugs]

Great! Now I need to dig through the axle sprockets and see how many teeth they are. If you can help me with my timing, jetting, tire pressures and launch revs I might be able to get down the track in style.

Thanks Pete.