Service

SERVICE

How low can you go?

I own a 1994 Honda XR650L dualpurpose bike. Although I am 6-foot-1 and can put both feet on the ground when astride the bike, I can’t help but feel that the overall handling would be greatly improved if the bike were about 2 inches lower. Is there any way to accomplish this without spending a small fortune on a new shock and fork springs?

David Walicek Yoakum, Texas

You mentioned neither your weight nor the aggressiveness of your riding style, both of which are important factors to consider when addressing this problem. But, unless you ’re well up into the 200-plus-pound range and ride your XR650L like an off-duty supercross star, dropping the ride height a little more than an inch is an easy job that involves no expense whatsoever. You can lower the front ride height by simply sliding the fork tubes up through the triple-clamps about an inch. And you can drop the rear as much as an inch and a half by backing off the preload on the shock spring. Just make sure the front wheel doesn’t hit the inside of the front fender when the fork reaches the end of its travel, and that the rear suspension isn’t so lightly preloaded that it bottoms out over every bump it encounters.

I think you ’ll be pleasantly surprised at the difference in handling when the XR-L is lowered just an inch or so. Al> though it will be more likely to bottom on big whoops and jump landings, it will turn more quickly and easily, and be noticeably more maneuverable in tight quarters. It also will allow you to get your inside foot on the ground more easily when making slow, sharp turns on steeply cambered surfaces. If however, you feel that the bike is still too tall, lowering it farther will be a much more expensive proposition. No question is dumb if you don’t know the answer, and it sounds like there ’s a lot of people in your neighborhood who fit that description. On Hondas and all Japanese motorcycles that use dipsticks, the oil should be checked by just sitting the dipstick > atop its hole with the bike in a perfectly vertical position on a flat, level surface. Do not screw the dipstick down into the hole or you ’ll get a reading indicating that the oil level is significantly higher than it actually is. I have a ’98 Harley-Davidson Heritage Softail Classic and am interested in increasing its horsepower output to cope with the high mountain passes that are common here in the West. Most riders and H-D shops suggest a change in the stock air filter, carb, cam and pipes. I’m interested in an increase in power, but not at the expense of having a louder machine. How can my Heritage Classic’s horsepower be increased while still maintaining a near-stock level of exhaust noise?

Paul Dean

Engineheads unite

Can’t you people get it right? In all of your articles, you invariably talk about a bike’s “motor.” But in truth, a motor is a means of accomplishing work that draws upon an external source of energy-such as an electric motor, which requires a battery or an extension cord. The means used in motorcycles (and in cars, planes, ships and some trains) are self-contained, internal-combustion devices properly called “engines.” I’d expect a magazine of your stature to know better. Craig I. Sherman

Boulder, Colorado

You are absolutely correct. But any engineer worth his pocket protector knows that over the past half-century or so, the use of the word “motor ” to describe an internal-combustion powerplant has been deemed perfectly acceptable and often even preferred. Besides, did you happen to notice that the transportation devices under discussion in this magazine are called motor cycles? Just look at the names of the companies that manufacture them: Honda Motor Co., Kawasaki Motors Corp., Yamaha Motor Corp., Suzuki Motor Co., Harley-Davidson Motor Co. None of these companies is in the electric motor business, but they all make motorcycles. Go figure.

Dipping the stick

This may sound like a dumb question, but I’ve not been able to get a consistent answer from anyone: When checking the oil in a Honda CB1000, should the dipstick be screwed down or just dipped in? Eric Kahn

New York, New York

The ABCs of GPzs

I recently took my 1995 Kawasaki GPzllOO into the local dealer for a major service. Mostly, I wanted to make sure the valves were correctly adjusted. When I asked the mechanic what he had found, he said that two valves were loose and two were tight, so he just swapped the shims and they happened to be just right. I think the valves were better before he did this, though, because the engine doesn’t seem as strong after this latest service. I’m not that smart, but I wonder how valves get too tight. Can shims actually tighten up? Paul Hargis Sierra Vista, Arizona

Shims themselves don’t tighten up, but a valve can change its clearance in any of several ways. The clearance increases when the top of the valve stem gets worn down or slightly flattened due to the constant impact of being banged open, or when the shim and/or the cam lobe wear sufficiently. Conversely, the clearance decreases when the constant impact of the valve slamming closed against the valve seat causes the head of the valve and/or the seat to become slightly recessed. This allows the entire valve to be positioned slightly closer to the cam or tappet when it is fully closed.

Your belief that the engine ran better before its most recent valve adjustment indicates that your mechanic may have botched the job. His explanation of the serendipitous, two-fortwo shim-swap business also smells a bit fishy. If he’s a really good, conscientious mechanic and you explain your concerns to him, he’ll recheck his settings. If he’s not, well...

Stealthtail

Paul B. Holden Providence, Utah

If you re looking for the best combination of power and quiet, it ’s tough to beat SuperTrapp mufflers. They suppress exhaust noise by forcing the escaping gases through the thin spaces found between special discs stacked at the end of the muffler. By either adding or subtracting discs, you can quickly and easily change the tuning of a SuperTrapp for a high degree of muffling, a high degree of performance, or just about anything in between those extremes. In addition to bolt-on mufflers, SuperTrapp also makes entire exhaust systems, one of which (part No. 62878062) is a 2-into-l style specifically designed for the Heritage Classic.

Gimme a brake

My question is more technical than service-related: If all other things remain equal and a bike’s brake mastercylinder piston is reduced in diameter, will there be more or less braking force for any given amount of pressure at the lever? Thank you in advance for your answer. SPuglisi

Posted on America Online

There would be more braking force at the front wheel, but the lever would have to travel farther to generate that force. If you apply, say, 50 pounds of force on the lever, and the mastercylinder piston has an area of 1 square inch, the total force exerted on the brake fluid (and, as a result, on the brake-caliper pistons) will be 50 pounds per square inch. If the lever pressure remains at 50 pounds but the master-cylinder piston area is reduced by 50 percent, down to one-half square inch, the total force on the brake fluid will be doubled to 100 pounds per square inch. But when the area of the master-cylinder piston is cut in half it will displace only half as much brake fluid. Consequently, the lever would have to move the mastercylinder piston twice as far to engage the caliper.

Obviously, any actual increases or decreases in master-cylinder piston diameter are not as dramatic as this hypothetical example; but even when the changes are smaller, they still deliver the same kind of proportional results. □