Jump to content
Sign in to follow this  

XR 200 sprockets and gearing

Recommended Posts

What is stock gearing on a 1990 XR200. Do all 200's use the same front sprocket. Also on the subject of gearing how would you figure out final gearing change when going to an 18" rear wheel and a trials tire. I think bicycle racers have a formula to figure how many inches each crank revolution is. Just thinking. Nearing the end of my 200 weight reduction project will post pics soon. Thanks.

Share this post


Link to post
Share on other sites

I have some bad news on your weight reduction program; a TT weighs about a pound more than a 18" knobby and more than that compared to a 17" knobby, also the 18" rim is heavier than a 17".

Stock gearing is 13/47, simular overall gearing with an 18" TT would be 12/47.

If you want to be more precise answer you should calculate counter shaft revs per mile for each combination of tire and gearing. Just a little arithmetic: start by measuring the tire rolling circumference. Roll the bike, with you on it, one tire revolution and measure the distance the tire traveled, divide by 12 to convert to feet, and then divide into 5280 to get tire revs/mile. I have 874rev/mi for my IRC 100/100x17 and 810rev/mi for my Dunlop 803 4.00R18.

Calculate the final drive gear ratio by dividing the counter shaft teeth into the rear sprocket teeth. 47/13 = 3.62 and 47/12 = 3.92. multiply these ratios times the tire rev/mi to get countersahft revs/mi. Comparing countershaft revs per mile for the different combinations shows 47/13 with a 17" to be 3,164 and 47/12 with a TT to be 3,175. Very very close, only 0.3% difference. This so close that you won't be able to tell riding the bike, except the TT will feel like less power because more traction feels less exciting.

Share this post


Link to post
Share on other sites

Thanks Chuck

I kind of got there but in a rather crude and less accurate method. I'm starting out with 12 / 48 cause that's what I have. My XR 200 weight reduction project is almost done and should be about 202lbs. wet no fuel. I tried to duplicate your project and take advantage of your research. your vast motorcycle knowledge is incredible. Thanks

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...