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Paul Dean

Just for the hill of it

Is there any way I can retune the engine on my 1993 Kawasaki KX250 motocrosser to give it more midrange power? It sometimes gets me into trouble when I’m hillclimbing. It either delivers way more power than needed or it bogs out and leaves me screwed in the middle of a hill. Keeping it in the powerband is pretty tricky; and when it falls off the bottom end of the powerband, I’m done. Are there any carb or exhaust changes that can give the KX a more even powerband? The bike is all stock, and the elevation here is 5000 feet (if that matters). I’d like to keep the bike if I could make it more like an enduro bike. Scott Nye Evansville, Wyoming

If hillclimbing is your preferred activity, you don’t want less power; you simply want to make the power your KX already produces more controllable. So, you don’t want to detune the engine to typical enduro-bike specs, which could reduce the power output enough to greatly compromise hillclimbing ability.

You can, however, gain considerable engine tractability without a loss of by installing additional flywheel weight on the KX's small ignition rotor. I know of two companies currently making weights that attach to the stock rotors on most popular motocross engines. One is Steahly Off Road Products (9950 SE Bull Run Rd., Corbett, OR 90719; 800/8002363), whose weights thread onto the rotor end of the crankshaft. The other company is A-Loop Offroad (3911 Norwood Dr., #G, Littleton, CO 80125; 303/791-0035), whose weights are welded onto the rotor. Both companies offer weights in different sizes so you can fine-tune the engine’s overall flywheel effect. I suggest you call and ask which weight they recommend to suit your needs.

There are pluses and minuses with each type of auxiliary weight. The ALoop style is more foolproof, since it can’t accidentally come loose; but you have to send your rotor to A-Loop to have the weight installed, and if you want to convert your KX back to motocross trim, you have to buy another rotor. The Steahly method allows you to remove the weight if you wish, or to have more than one size weight without also needing separate rotors; but because they thread on, there ’s always a chance they might come loose.

Either way, try solving your problem with flywheel weight before attempting any other retuning of the engine.

Bucks up, power down

Could you please explain why, after nearly $3000 worth of engine work on my 1995 H-D Low Rider, I still can’t keep up with my friend’s 1400 Intruder, whose only modifications are a jet kit and pipes. It’s especially frustrating in the midrange and top end, and I even have five transmission speeds to his four. 1 still prefer my Harley for its comfort-I’m 6’2”-but it’s hard to watch him pull away through the corners on roll-on acceleration. We have nearly identical displacement, 1360cc on the Suzuki compared to 1340cc for my Harley, so what’s the story? Mark Murphy Aptos, California

You included no specifics about the modifications to your Low Rider’s engine, so I can 't assess its impact on performance. But $3000 worth of engine work doesn’t guarantee anything besides a reduction in your bank account. Even though the Harley aftermarket offers a practically unlimited selection of performance equipment, the net effect of an engine hop-up can be disappointing if the individual pieces are not selected judiciously and with a specific goal in mind-more midrange power or top-end-power or the broadest powerband, etc. Harley riders often make the mistake of installing the hottest cam, the biggest carb, the loudest pipes and the trickest heads, only to end up with an unsatisfactory boost in performance.

Also remember that the Intruder has a much more modern engine design than the Harley. Its overhead-cam, three-valve-per-cylinder, twin-carb, light-flywheel engine was designed from the outset to offer snappy V-Twin performance. The Harley engine design, while one of the most beloved powerplants ever built, is based on 1930s technology and has some performance limitations as a result.

Still, for $3000, your H-D Low Rider shouldn 't just run with the 1400 Intruder; it should run away from it.

Tires for torts

I own a ’94 Suzuki GSX-R750 that has a 3.5-inch-wide front rim and a 5.5inch rear. Would there be any disadvantage to fitting a 120/60-17 tire up front in place of the stock 120/70-17, and a 190/50-17 in the rear in place of the stock 180/55-17? I’ve called Suzuki, Dunlop and Yoshimura, but all I get are lawyer-rehearsed answers. Can you give me a “straight” answer? I promise I won’t sue you. John LaRusso Ú.S. Armed Forces, Germany

Mavbe you haven 't gotten the right answers because you haven’t asked the right questions. Such as, which brand and model of tire do you intend to use? What kind of riding will you do with this setup-fast street riding, canyon carving, actual roadracing? Without this kind of information, no one can give you a definitive answer.

I can, however, tell you about the phvsical changes that will occur. The lower-profile tires will lower the front axle approximately 12mm and the rear axle 4mm. This will steepen the steering-head angle by about 1 /¡-degree, effect a 6 or 7mm f/4-inch) reduction in front-wheel trail and slightly quicken the steering. The 190 rear tire is intended for a 6-inch-wide rim, so your

5.5incher will pinch the sidewalls in slightly and alter the intended tread contour The overall effect of this swap is hard to predict, but, depending upon your selection of tires, there is likely to be no detectable improvement in handling and some perceptible loss of it.

If it were my bike, I wouldn’t do it. And I wouldn 't sue me, either.