Here's another thought.  The RYCA has a pretty tight belt clearance situation:
-- the top and bottom of the belt when it gets close to the drive pulley
-- at the swingarm if you are using one of the RYCA modified swingarms and an old-style 4.00-18 tire like my Avon Speedmaster.  There is a very narrow range where the axle is forward enough to not overtighten  the belt when you hit a bump, and rearward enough to not rub on the swingarm.

If you install a pulley that is a 1/3" larger diameter, 1/6" (approx .017") larger radius, this would complicate the issue.

You'd need a longer belt maybe.  I'd be surprised if there is a 1/2" longer belt available.

Drifter wrote on 10/12/12 at 07:57:46:


I have the measurents at home....I will post the part number and dimensions when I get home.

There are industrial belts available in different lengths, but you'll pay a premium for them.

The savage belt has 133 teeth.

next size up is 135, then increment in 5's.

Gyrobob wrote on 10/12/12 at 12:17:57:

One toothlength * cos(angle between countershaft/axle line and belt)

That is close but not 100% accurate for reason too lazy to type.

Who makes the belt?  Gates?  Kelly Springfield?

I measured the new pulley....and calcuted the diameter of the stock pulley so I don' have to take mine off.

The 25 tooth pulley has a circumference of 347mm as measured with a cloth tape, and the calculated diameter is 110.45mm.  If I calculate the reduction from 25 tooth to 23 tooth it provides a circumference of 319.24mm, and a diameter of 101.61mm.  This makes an increase of the new pulley radius of 8.84mm (0.1738").....or just a tad less then 3/16".

The pitch of the teeth appears to be 13.88 mm - so getting a belt with 2 more teeth would lengthen the distance to the rear wheel by the distance of one tooth (13.88 mm or 0.54")....so the longer belt would move the rear wheel back (0.54" - 0.1738" = 0.3726")....or about 3/8".
(Update:  I just read a following post where the tooth pitch is 14mm and not 13.88 as I calculated....and I suspect the difference is the diameter of the belt on top of the hub....or the innacuracy of the cloth tape).

I measured the hubs on both the stock 23 tooth and the 25 tooth, and it is necessary to remove 0.368" from the front of the hub and 0.183" from the back of the hub.  I checked my measurements as it was hard to get a good reference point with the calipers I have....and the to distances checked within 0.045".....so that is my accuracy error and when I get them machined I will take both pullies.  I have a friend that thinks he can machine it on a lathe....it will take carbide bit inserts and from what I have read.....it takes a few of them.

Dave said, "I measured the hubs on both the stock 23 tooth and the 25 tooth, and it is necessary to remove 0.368" from the front of the hub and 0.183" from the back of the hub."

Do you really have to remove about a 1/2" from the pulley hub area from side to side?  That would seem to be asking for some variation in keeping the pulley perfectly perpendicular to the axis of rotation. I suppose, though, if the pulley is a tight fit on the spline, this won't be a problem.  I'm just curious as to why kawasaki thinks there needs to be so much more contact area on the spline.

That's going to be some really hard metal, I think I might rough it down with a grinder first and then give the carbide cutting tools a try to take the final few hundredths off. Since it goes on with a nut, you should be able to fix small spacing errors with shims, better to not need them but looks like it should work.