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JOE MINTON

Tired CB400

I am currently restoring a 1975 Honda CB400 Super Sport, but when it comes to the choice of tires,

I am at a loss. I’d like to install a set of modern tires, but would today’s tires cause problems with yesterday’s frame and suspension technology?

Don Crosthwait Ogden, Utah

It is conceivable that you could have a problem if you fitted tires that were very wrong for your particular motorcycle. Your CB400 was developed using tires with a round cross section. Those tires, in turn, were designed for use on relatively narrow rims. If you were to fit a set of low-aspect-ratio, oval-cross-section radiais onto the CB400's narrow rims, well, there is a good chance that the bike would become unstable at high speed.

Fit a set of premium-quality biasply tires that have the same shape and size as the originals. Bridgestone, Continental, Dunlop, Metzeier and others make such tires.

Still, even these tires may develop enough adhesion to give your stock suspension trouble. You may find that your CB400 will move around a bit if you ride it hard with very sticky tires, especially if you haven 7 refurbished the bike's suspension. To fully take advantage of modern tires, you 'll want to make sure the rear shocks and fork springs are up to snuff.

California pipes

I recently purchased a used, 1986 Kawasaki Ninja 600. I live in New York state, but the bike was originally sold in California. The guy then moved to New York, stored the bike for a few years, then sold it to me. Now comes the burning question: Are the exhaust pipes unnecessarily restrictive in order to meet California anti-pollution regulations? If so, is there an easy way to “unclog” the pipes, or do I need to invest in a new set of pipes? Nobody around here seems to know any of this.

Dave Wiedrich Holcomb, New York

The only difference between a 1986 California Ninja 600 and those sold in the rest of America was the charcoal canister fitted to California models. The canister traps gasoline vapors that would otherwise go into the atmosphere via the fuel-tank breather, and feeds them to the engine instead.

Normally, the presence of the canister has no effect on performance. However, if you overfill the tank to the point that gasoline runs into the canister, your engine will run very rich until the gas in the canister has evaporated into your engine.

What’s damping do?

Recently, I purchased an incredible bargain, a 1 984 Yamaha FJ 1 100 with 2500 miles on the clock. So, I have this beautiful sporttouring bike in my stable. My one problem? What the heck is this damping business all about on the front end? When I got the bike home, I found the two damperadjusting knobs in different positions! I consulted with my racing friends and still don’t have a clue. My local Yamaha shop wanted to take the fork apart to see if the dampers were working. Do these things do anything? If so, how do I adjust them?

Jack O'Riley Delano, Maine

The knobs adjust the amount of rebound damping in the fork legs. The higher the number, the more rebound damping you 'll get. Increased damping slows the rate at which the front wheel will return to its normal position after it goes over a bump. The nature of the road, the speed of the motorcycle, how you 're riding (charging or cruising) and your own preferences about ride qualities will ultimately determine where you set the damper knobs. You may find that you 'll want them in one position for traveling on the interstates and another when riding hard. Light damping (lower number on the adjusters) will give the better ride when cruising on a smooth highway. Heavier damping generally gives more control when one is charging down a twisting, bumpy mountain road.

Unfortunately, the actual damping value of each adjustment position is effected by the fit between the Teflonimpregnated bearing located at the bottom of each fork tube and the slider it rides in. A loose fit will reduce the damping effect because of fork-oil leakage past the bearing. This leakage can be so great as to render the damping adjusters completely ineffective. If you cannot tell the difference between the lowest and highest damping positions, your bushings are probably loose and need to be replaced. Both fork legs should be adjusted to the same damping number, assuming, of course, that the damping of each fork leg is perfon 11 ing correcti y. ©