Service

SERVICE

Foul play

Paul Dean

I need some technical advice regarding sparkplugs for my '93 Honda ST1100 with 10,000 miles on the odometer. The owner’s manual specifies an NGK CR8EH-9 plug for regular riding, but I can’t get more than 3000 or 4000 miles on them before they begin misfiring under a heavy throttle load or above 5000 rpm. Only a fresh set of plugs cures the problem. The bike is otherwise in good and standard condition, and uses no oil.

This problem could be related to the fact that I ride the bike to work every day in heavy traffic. I assume Honda designed the ST as a high-speed sporttourer intended for extended highway use, but I hardly ever get it above 5000 rpm. Sometimes, if the misfiring hasn’t progressed too far, I can “heal” the problem by riding above 5000 rpm on the open road for a while. But it always returns when 1 revert to my usual riding pattern. An inspection of used plugs reveals darker-than-usual color as evi-

dence of their being too cold for my usage. The owner’s manual mentions a colder plug, a CR9EH-9, but not a hotter one. What are my options?

Marcos Agosti Caracas, Venezuela

Although the ST1100 does not have a history of fouling sparkplugs when run at lower rpm, the symptoms you describe indicate that your bike is suffering from just such a condition. A nr’ I gather it is doing so on all cy linde* A weak spark or an excessively rich fuel mixture would he the most logical causes, hut the odds are astronomical against all four of your ST's curbs or both of its ignition coils developing the very same symptoms at exactly the same time. The 3000-foot altitude at which you ride will tend to make the carburetion a bit rich, but not enough to cause sparkplug foulingunless it is combined with the slow riding you routinely do for long periods in heavy traffic. Under those conditions, the heat of combustion at lower rpm might not be sufficient to keep deposits from accumulating on the plugs ' insulators.

The first thing you should do is check the condition of the air-filter element; it is not scheduled for replacement until the 12,000-mile mark, but it could be clogged just enough to contribute to the fouling problem. And also verify the ignition timing; a retarded spark can lead to incomplete combustion and subsequent plug fouling. If the air filter and the ignition timing prove to be all right, then-and only then-switch to an NGK CR7EH9 plug, which is one heat-range hotter than your ST's stock plugs.

Cattywampus cruiser

1 really love my new Suzuki 1400 Intruder, but it has one very strange characteristic that three Suzuki dealers say they don’t understand: If I take my hands off the handlebar at just about any speed, the bike immediately leans to the left and then starts turning slightly to the left. This never happened with my 800 Intruder. It takes so little pressure on the right handgrip to keep the bike going straight that you don't notice the problem until you take your hands completely off the bar. 1 discovered this in the first week of ownership, so it isn’t the tires, and the dealers say it isn’t alignment. It’s not knowing what the problem is that bothers me more than the actual characteristic. 1 will appreciate any advice you might be able to give me.

Dick Brown South Colby, Washington

Three things can cause a bike to steer one way or the other when the rider takes his hands off the grips: 1) the rear wheel is not in perfect left/ right alignment with the front wheel; 2) either or both of the wheels are not perpendicular to the ground when the rest of the motorcycle is perfectly verdeal; and 3) by a quirk of its design, the bike caries more of its overall weight on one side than on the other.

Your dealers have told you that the alignment is correct, but I don 't know how they checked it or whether they were referring to alignment as l described it in Example 1 or Example 2. In either case, the alignment needs to be verified by a more sophisticated method than just eyeballing it. And if alignment is found to be the culprit, the problem then should be referred to the U.S. distributor, American Suzuki, since this would seem to be an error that occurred during the bike ’s manufacture.

Interestingly enough, the last 1400 Intruder l rode also steered very slightly to the left, and my check of wheel alignment with a straightedge revealed no disorder of any kind. I also have observed this kind of slight “pull” to one side on numerous other shaft-driven bikes over the years; when no wheel misalignment was found, I concluded that the symptom was the result of Example 3.

It 's not entirely uncommon for a bike to weigh a bit more on one side than the other, largely due to the engine; designing a bike so the weight of its many engine and driveline components is distributed evenly from left to right often is virtually impossible. One of the more notorious cases was the BSA Twins of the '60s and early '70s: They had so much more weight on one side than the other that the front wheels were designed to be laced off-center to help compensate for the left-righ t i m bala nee.

If, as you say, this slight pull to the left doesn 't bother you, I suggest you just forget about it. Rectifying the problem could prove more difficult than living with it.

Speed king

Would you please explain to me how you come up with the top-speed figures in your road tests?

Here's the reason I'm asking: I have a 1992 Suzuki Katana 750, and in the 750 shootout you published in that year, you listed the Kat's top speed as 139 mph. Then, in the September. 1994, test of the Honda CBR900RR, you said its top speed is 158 mph. Well, during a recent roadrace school at Road Atlanta, I was clocked at 157 mph on the back straight on my Ka tana, which is perfectly stock except for a Vance & Hines SS2R exhaust. Please explain, because I know that a CBR is faster than my Katana, even with my bike’s modified exhaust.

Mike Cressweil Woodstock, Georgia

The top-speed figures we publish are each bike 's actual performance numbers. They re clocked with a stateof-the-art, high way-patrol-approved radar gun on a three-mile-long, flat stretch of asphalt that's only a few hundred feet above sea level. The gun is recalibrated before each day's use, and every bike makes several runs in each direction to compensate for any ambient wind; if there's a significant discrepancy between the speed in one direction than in the other, the numbers are averaged.

Under those conditions, 157 mph on your 750 Katana is completely out of the question, with or without a Vance & Hines silencer. On the other hand, most of Road Atlanta's back straight is a long, steep downhill that's the fastest part of the track; so, with a good, strong run off the previous turn, your Katana would probably go considerably faster than 159 mph.

But not 157. / have to believe that the person who was clocking bikes on the back straight that day either inadvertently gave you someone else 's speed or was using faulty equipment. Your tach holds the truth: If it was not hovering right at its 12,500-rpm redline at Road Atlanta, you were not going 157 mph.

Boyer boo-boo

In your November, 1994, Service column, you printed a letter from a reader who advised the use of Boyer electronic ignition systems on older British bikes. That was a useful piece of information, but you forgot to give the name and address of the company that sells the ignitions, and I haven’t been able to find one around here. Can you tell me where or how can I get these ignitions? Jeff Weisner Duluth, Minnesota

Sorry for the omission. Quite a few companies are currently importing the British-made Boyer ignition systems into this country, but most of them sell only to dealers rather than directly to the public. You should be able to buy a Boyer ignition through any British bike shop worth its salt. E3