Service

SERVICE

Paul Dean

Fuel infection

A friend of mine has just purchased a Suzuki TL1000S and is having some problems with the engine sputtering and spitting when idling and at low speeds. The symptoms clear up, however, when the bike gets up to speed. He has checked with the local Suzuki dealer, and they claim they don’t have any solutions to his problem. In some recent issues of various bike magazines, I think I recall reading that Suzuki was aware of this problem and that the solution was a matter of remapping the electronic fuel injection or something of that sort. Since the dealer couldn’t help him, can you?

D.L. Barlow Benicia, California

Since the date on which you mailed your letter, American Suzuki has issued its entire dealer network a service supplement that describes, in great detail, the proper procedure for tuning the TL1000S. This procedure includes, among many other recommendations, two critical steps in tuning the electronic fuel injection: getting the throttle bodies in perfect synchronization, and accurately adjusting the throttleposition sensor. Suzuki representatives

claim that if this procedure is closely followed, any carburetion-er, make that injection -glitches in the TL’s engine performance will be minimized. Notice that they said “minimized not “eliminated.” In some cases, they > explain, the engine might not have the same seamless, surge-free character as some other bikes might, even if the procedure is followed to the letter. The TL is in a high state of tune, with huge throttle bodies and racy cam profiles; depending upon atmospheric conditions and normal production-line variations between individual models, any given TL1000S might exhibit a slight bit of midrange surging, but most should run cleanly.

Dyno-sores

I have a question about dynamometers. After careful break-in of my ’97 Honda CBR900RR, I took the bike to a well-known high-performance shop to have a Vance & Hines 4-into-l racing exhaust installed, along with their CBR kit that includes jetting, air filters and airbox modifications. They also installed a shift kit at the same time. Before working on the bike, the shop ran it on the dyno and got peak readings of 91 horsepower and 55.6 foot-pounds of torque. After the modifications, the dyno showed 99.9 peak horsepower and 59.4 foot-pounds. Compare this to Cycle World's, test of a stock 900RR, which showed 113.7 horses and 65.3 foot-pounds of torque.

I understand that these readings were taken on two different dynos and that, as such, those dynos will give different readings; but a 22.7 horsepower difference in stock trim seems an unusually big discrepancy, as does nearly 10 foot-pounds of torque. Even after the modifications, my bike still made 13 horsepower and 5 foot-pounds less than your testbike. Could you please shed some light on this for me?

John R Perry Windsor, California

The question here is simple: Is your CBR900RRs engine much less powerful than normal, or is its power being measured on a dyno that gives readings that are much lower than normal?

With the limited information you ve supplied, I can’t offer a conclusive answer. I don’t, for example, know what kind of dyno the shop in question is using. All of our tests are conducted on a Dynojet rear-wheel dynamometer, and the horsepower/torque numbers it yields are reasonably comparable to those produced by the same models of motorcycles that have been tested on other Dynojet units. If your shop is in fact using a Dynojet, that particular dyno could have a software or calibration problem that is producing low readings. Or, the dyno room may not be adequately ventilated, or their chassis tie-down method may be allowing excessive slippage between the rear tire and the dyno roller. And if their dyno is one manufactured by someone besides Dvnojet, low readings could be characteristic of that type of dyno. All of which illustrates why comparing results from two different dynamometers is guaranteed to produce more futility and confusion than anything else.

Actually, your dilemma can be resolved quite easily. Just ask the shop to let you see the dyno results of other stock bikes they’ve tested, then compare those numbers to the ones we’ve published in Cycle World. If their numbers are consistently lower than ours, the difference in dynos is the obvious cause. But if their numbers are comparable to ours, you ’ll then know that something is not right with your 900 ’s motor.

Radical radials

My 1996 Suzuki Katana 600, which still has the stock 17-inch tires, uses a 3.0-inch-wide rim on the front and a 3.5-inch-wide rim on the rear. I want to try radial tires on it, but all the bike and tire manufacturers have always cautioned against doing so because radiais require wider rims. Dunlop and Metzeler, however, with their new D205 and MEZ2 sport-touring radiais, respectively, now have radiais in the 110/80 front and 140/80 rear sizes that correspond to my stock tire profiles. Will these tires work properly on my Katana? I think they would, but I’ve gotten conflicting answers from everyone I’ve asked. Robert Piszkin Oceanside, California

They indeed will work very nicely, having been designed for narrow-rim bikes just like yours. But as far as sizes are concerned, Metzeler recommends a 150/70ZR17 MEZ2 for the rear of your 600 Katana instead of the stock 140/80 size. This same recommendation holds true for Pirelli, which-with its MTR03 front and MTR04 rear Dragon GT series-also makes narrowrim radiais. The 110/80 front tires will work on a rim anywhere between 2.15 and 3 inches wide, and the 150/70 rears are suitable for rims between 3.5 and 4.5 inches in width. O