Boxerworks.com

On Thu, Mar 8, 2012 at 4:49 PM, Alex <alexgoodhart@ymail.com> wrote:


In building a 1974 R90S I am seeking advise of former racers/ cafe etc. I will be using a set of very light Kuma Magnesium 5 spoke wheels similar to Morris. The fork is a reworked R100R with Gold vale and linear springs for my weight. I know lighter is better but not sure which way to go. If I use the stock 4 piston calliper's from the R100R I will need custom 285 mm rotors to work with the 5 bolt hub of the r90s wheel and the 25 mm Axel. This will weigh more but give strong braking?

Another option would be to use the g/s 320mm conversion that uses one of the same calliper's and a adaptor to hold the calliper as well as an adepter to move the flat 320mm rotor to fit. This would be lighter I think not sure how good a brake?

The last option would be to use the stock R100R spoke wheel with stock R100R rotors and callipers. This wheel with rotors weights about the same as a snowflake with rotors.

My goal is to retain the nibble feeling of the stock R90S but with better braking and handling. Frame has been extensively braced. Motor is 1050 cc twin plug 9.5:1 336 cam can run Dellortos or round Mikuni?

Any feed back from someone who has done mods would help.

You are the first person who accused the R90S of being nimble.

Charles is running Dels on his 1070 with good results.

How far along is this bike? Do you already have the wheels? If so, the R100R wheel and the mag wheel will not make a set, at least visually.

Will you be willing to share with us the bracing? How did you brace the front, near the head tube?

Chuey

I'm not sure just how much ability/money you have, but here's what I'd want to be able to do:

Unsprung weight = Bad

Really good brakes = Good

Modern calipers are designed to work with very thin rotors. Those rotors weigh a fraction of what old style rotors weigh. Modern Brembo Goldlines would be fine; no need to go with independent 4 pad calipers or anything, but a radial master cylinder would be nice. Bracketry for the calipers wouldn't be difficult, but disc carriers could be.

Of course, the easiest and most common way to accomplish this is to put an entire modern front end on the bike.

Of all the mods/upgrades/yada yada/ I've read for hotting up airheads, I've not seen one for testicles.

ME 109 wrote:Of all the mods/upgrades/yada yada/ I've read for hotting up airheads, I've not seen one for testicles. :mrgreen:

Some may have gotten those as OEM parts.

vanzen@rockerboxer.com wrote:

ME 109 wrote:Of all the mods/upgrades/yada yada/ I've read for hotting up airheads, I've not seen one for testicles.

Some may have gotten those as OEM parts.

Yes, but like all performance parts, they get old.

Where did you get the Kuma wheels? Never heard of them for Motorcycles let alone airheads.
If they are very light, how light? Can you get weights?
There are K bike front ends that will fit on an Airhead quite easily. Might be a more cost effective route if you want better brakes, suspension, etc. They come up on eBay every once and a while for cheap. If you already have most of the parts, my hats off to you.

Duane Ausherman wrote:You are the first person who accused the R90S of being nimble.

He said "nibble". That must be a technical term describing that sideways chatter in tight turns.