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Twenty questions

Modern or current motorcycles are of good quality. However, many good design features have disappeared. Could you explain the following: 1) What ever happened to the quick-detachable rear wheel that could be removed without disturbing the chain or sprocket? 2) What is the reason for short mudguards (fenders)? The street machines of 25 years ago had good splash protection. 3) Why do manufacturers categorically refuse to provide fully enclosed chains? 4) What is wrong with kickstarters? They are simply lighter, and cheaper than electric starters. If someone is too weak and wimpy to crank it up, they should not be riding. 5) Why are Japanese bikes so heavy? 6) Why are so-called perimeter frames so in vogue? 7) Are cast wheels better, or are they just cheaper to manufacture? 8) Formerly, sport/touring bikes had large wheels for good handling ( 19-inch front, 18 rear). Now they have small wheels. Why? 9) According to P.E. Irving’s Motorcycle Engineering, a small cross-section tire does better with respect to resisting deflections to the side than a wide one. Why, then, are fat crosssections now in vogue? 10) Why are smaller gas tanks popular? 11) If the manufacturers must put on cast wheels, what is the reason for the ox-cart look? Isn’t the snowflake look of the BMW circa 1978 better?

12) Why did fork boots disappear? They kept out dirt and water. Is it fun to disassemble the forks to put in seals?

None of my buddies know any of these answers, either. Perhaps you could come up with some good ones.

P. Scott

Knoxville, Tennessee

Good questions, but YOU 'd better be careful: If you put your tongue any further in your cheek, curmudgeon detectors everywhere may start ringing. But for some brief answers:

l) Quick-detachable rear wheels on Japanese bikes died with Suzuki's true-enduro bikes. They are convenient, somewhat heavier than the standard design, and simply haven 7 been a priority on recent street bikes, perhaps because tire repair is less called for these days.

2) Short fenders are simply a styling concession. Also, not that many modern motorcyclists ride much in the rain.

3) Fully enclosed chains make wonderful sense from an engineer's point of view, but their styling has never been accepted. Also, the ones that have appeared often leaked, and bizarre as it may seem, that may have been less acceptable to riders than the oil spray from a normal chain.

4) Nothing is wrong with kickstarters except that the majority of motorcyclists no longer want them.

And if a bike already has an electric starter, the addition of a kickstarter would add cost, weight and complexity for something that would serve only as a backup.

5) Japanese bikes aren 7 heavy in proportion to their power. A Japanese 450 makes at least as much power as a Triumph 650, and weighs roughly the same. By that standard, a Suzuki GSX-R is exceptionally light.

6) Twin-spar frames, such as on Yamaha's new FZR1000, are simple, strong and direct structures, and as such are good frame designs. Other types of perimeter frames employing small tubes may have less to be said for them, but they certainly are popular. Sales appeal is often a consideration in motorcycle detail design.

This was as often true in the British era as it is now.

7) Cast wheels are stiffer and require less maintenance than spoked wheels. More importantly, they can be used with tubeless tires. But spoked wheels are a more efficient structure, and can be lighter than cast wheels. As for cost, we're not sure which is less expensive to make, but economy models in a given range usually have spoked wheels.

8) Larger-diameter tires generally offer better stability on rough or unpaved roads. Australian motorcycle journalists, who frequently have to deal with bad roads, are not fond of bikes with 16-inch front wheels. But on well-surfaced highways, 16or 17-inch wheels can offer an excellent compromise between steering effort and stability.

9) Irving is right: Narrow tires are less deflected by bumps than wide tires. Wide tires may offer other benefits that make them attractive, such as longer life or softer allowable rubber because of their greater overall surface area. But some motorcycles on the market would handle better with narrower tires than they now have.

10) Smaller tanks are popular because they look good, and because not everyone wants to ride more than 100 miles at a sitting.

11) Beauty is in the eye of the beholder, and more spokes may or may not improve the appearance of a cast wheel. Functionally, the threespoke wheels currently used in GP racing are among the lightest cast wheels ever made.

12) Fork boots disappeared because mol ore vele bu vers like the look of shin v chrome more than of black rubber. Modern fork scrapers do a fair fob of protecting fork seals in unbooted forks, and the manufacturers realize that most motorcycle owners don't ride a new bike long or far or often enough to create fork-seal life problems. And in the end, more fork seals are probably lost due to landings from wheelies than to simple wear.

BSA clutch slip

I have a problem with my 1969 BSA 650. It has new clutch plates, but if I adjust the clutch cable to where it’s supposed to be, the kickstarter slips and the engine won’t turn over. If I loosen the cable to where the engine will turn over, I can't put it in gear. It’s been to two mechanics who can't figure out what’s wrong.

Ed Verville

Lakewood, New York

It seems as though the clutch pushrod inside of the transmission mainshaft is out of adjustment. To remedy the problem, back off the clutch-cable adjuster up on the handlebar until the cable has maximum slack. Now, down on the primary case, remove the big inspection screw that gives you accesss to the pushrod adjuster in the center of the clutch pressure plate. With a socket, loosen the locknut on that adjuster; then remove the ratchet and pass a straight-blade screwdriver through the center of the socket, into the adjuster screw. While holding the screw firmly in place, back off on the locknut several turns. Now, adjust the free play by turning the screw inward (clockwise) until you feel it just make contact with the pushrod, then back off on the screw a quarterturn. Cinch down the locknut as hard as you can by hand, then tighten it with the ratchet. After you adjust the free play in the cable, the clutch should work properly.

If it does not, then something in the clutch mechanism has been installed improperi y or is not the correct part. Considering that you have already had two "mechanics" fail to diagnose the problem, the easiest solution ultimately might be to take the bike to a BSA/Triumph expert.