View Single Post
Old 04-09-2012, 04:51 AM
Motorized Bicycle Elite Member
Join Date: Jul 2010
Location: CA
Posts: 1,754
Default Re: what did you do to your motor bike today?

Got close to putting the 47:1 ratio 6 pulley 2 jackshaft 3 belt to a test, but it got dark and will line up the pulleys better and see next time.

I looked at the approximate ratios as it goes Centrifugal clutch pulley about 2 inch to 10 inch top 1st jack shaft. This makes a Reduction of 5.

From that live jackshaft top across to a 2 inch pulley and on downward to 2nd lower jackshaft with 4 inch pulley. This makes a Reduction of 2.

From that live jackshaft back the other way across to a 2 inch pulley and back to the 10 inch drive pulley mounted on the rear wheel spoke for drive tire 26 inch diameter. (discounting the tire diameter just yet) This makes a Reduction of 5.

Approximate 5 times 2 times 5 equals 50 Reduction total. The more exact pulley sizes I recall I checked gave the ratio of 47:1.

Now if I were to want to switch from parade speed that the 50:1 makes about 3.5 to 5.5 mph with 2200 rpm to 3500 rpm, I’m looking at swapping the 2 inch pulley that goes to the 4 inch pulley reversed. This will be a gearing up of 2 then. So call it a divide by 2. With the other two ratios left the same as a pair of 5’s then, 5 times 5 equals 25. 25 divide by 2 equals 12.5 which make 14 to 22 mph with 2200 rpm to 3500 rpm. I’m going to want about twice that at a 25:1 ratio for 7 to 11 mph for some good hill climbing speed for dirt bike off roading.

Brain $^%U, an ahhha … all I need to do is take the 4 inch pulleys out and replace with a 2 inch pulley an extra to have around. Then 2 inch to 2 inch does neither gearing up or down. Then I retain 25:1 that I will have to see how it handles with the centrifugal clutch trying to get up to speed without heating up the clutch too much between to idle at 1750 rpm getting going 2000 rpm to 2200 rpm where the clutch shoes to be solid on the bell housing.


Last edited by MEASURE TWICE; 04-09-2012 at 04:57 AM.
Reply With Quote