Sprocket set up

[Blake73]

Im currently in the build process of my bobber.
Was just wondering what everyone was running sprocket size wise. Motor and rear wheel.
Currently running 21inch front, 18inch rear. Wheels.
Would like to have a good amount of highway time but dont want a total nugget down low.

 

[gggGary]

Stay with the 17 on the front IMHO 32 is about the minimum you want to go on the rear.

 

[pamcopete]

Here is a Excel spreadsheet that yields RPM vs MPH for all combinations of wheel size, sprockets and gears. Use the yellow pull downs to select the values you want. Instead of wheel size or diameter or circumference, this spread sheet uses rolling distance of the rear wheel. Roling distance is the distance that the bike moves forward for one revolution of the rear wheel. It is more accurate than diameter or circumference of the wheel because a motorcycle tire has an infinite number of circumferences due to its circular cross section.

http://www.amckayltd.com/xs650revs.xls

 

[5twins]

I agree with Gary, don't go any smaller than a 32T on the rear. Personally, on an 18" rear wheel, I prefer a 33T, just one tooth smaller than the stock 34T. That's how the European models came geared and I think they got it right. That gearing matches this engine's power output quite well.