Re-gearing for supercharger

[harvdog42]

Hello everybody,

I just registered and would like to start right in with a question. But first some background. I have a '79 standard and finally got my supercharger mounted and running on the bike. I'm drawing through an old Harley Kehien carb and compressing the mixture with an old Drouin centrifugal supercharger I bought from Ebay awhile back. The supercharger is blowing into a plenum. I'm getting about five lbs. boost which definitly increases power. The whole thing runs darn good believe it or not. My problem is gearing. The extra power from the boost can be felt most when the engine RPMs are lower. There must be a way of changing the gearing in these beasts! Or is there?

Jim

[sixtysix]

Only way I know of is chain conversion, a V-Max or old Venture gear should be the same but not sure if those ratios would be better or worse. Somebody here used a V-max rear end I think, try the search function and see.

[uk1.1s]

Re-gearing

Heard of some potentials - not sure of the suitability for what you are trying to do.

1. Someone in the UK used to drag race an XS11 and re-geared with a Virago rear spoked wheel - using v. heavy duty spokes (probably spent some time respoking often too!

2. You can fit a Yam Diversion 900 wheel in too quite easily, although this may not be a US model...something like a 600 Seca but bigger with shaft drive. Check out the Dutch XS owners club site for pics of a few specials there. Most with a modern looking rear wheel there are using 900 Diversion conversions.

3. V-Max conversion was discussed on this site a few months ago and someone sent on a picture of a rear wheel in place.....but tyre clearance to the shaft was a problem. Never heard whether any major work occured after this to correct this somehow.

4. The best if you want to play about with the ratios I expect would be a chain conversion. Haven't seen this on an XS for real - just in photos, but usually includes some sort of out-rider bearing so that an elongated output shaft from the gear box (onto which the drive spokets fixed) is supported.

Good luck - I'd be interested to hear what you try to help the gearing

[Dennyz]

FYI Vmax rear drive

The Vmax rear drive I looked at was lower geared (higher ratio) then the XS. The Vmax rear tire is also smaller diameter which would also increase the effective rear drive ratio.

[Geezer]

Yamaha used the hell out of that rearend. I'm pretty sure all the older XS shafties used the same one. The easiest way to go would be a taller rear tire but there's only so much room there too. I once bought a parts bike that had an 18" rear from a 750 on it. I can't recomend that as I don't know if the 750 rear wheel is really up to the job. If you can't live with out trying, I have one you can have for shipping costs.

Geezer Tony