The Service Department

THE SERVICE DEPARTMENT

JODY NICHOLAS

TUNING FOR TOURING

I now own a ’67 T100R, 500-cc Triumph. I wish to do extensive touring with two up and I thought a conversion to a single carb would make life a lot easier.

Does the T100C single carb manifold bolt directly to the T100R head? The dealers around here seem to be at odds about this.

I intend to use a series 376 monobloc with a 190 main jet, along with a 50 tooth rear sprocket.

Will these changes result in a reliable 60-mph tourer with a load of about 250-300 lb.? (That’s both riders and luggage.) Will there be a need for a timing change from the T100R specs?

R.J. Mills Vancouver, Canada

The conversion to a single carb will certainly make your bike more tractable, and should also improve the gas mileage somewhat. The T-100C intake manifold, 1968 or later, will bolt directly to your cylinder head, so installation should be a simple matter. Your choice of carburetor is a good one, but you may have to experiment with the main jet size to get it “spot-on.” Even identical machines often require main jets of different sizes to perform perfectly.

The 50-tooth rear sprocket sounds just about right for your use as it will allow the engine to develop more usable torque at lower road speeds, and you’ll still have no fear of over-revving in top gear. The standard final drive ratio of 5.4:1 is good for a light to mediumweight rider, but the machine gets sluggish in a hurry as the weight is added.

There is no need to alter the ignition timing from standard unless you will be traveling in Mexico or elsewhere where the gasoline is generally of a lower octane rating than is available in the United States or Canada. Even with a compression ratio of 9:1, your machine should run reasonably well <?n regular gas if it isn’t allowed to get too hot.

"KAWASOSCILLATION"

Recently my Kawasaki Mach Ill’s front end began oscillating from left to right, with each oscillation increasing in amplitude until the bike flipped over. I now have two less teeth, numerous cuts and bruises, and the expensive task of repairing my cycle.

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I have experienced this same type of oscillation (some people refer to it as speed wobble, I think) at higher speeds with every bike I’ve ever had, but was always able to get rid of it by either braking or relaxing my grip on the handlebars. This time I was only traveling at about 62 mph and, try as I may, I just couldn’t stop it.

I have examined the front end, but I cannot find anything to indicate a possible cause. The preceding day I had added an extra 2 lb. of air to my tires; could this possibly cause it? If so, why didn’t it happen the same day when I was driving at about 105 mph?

What causes this type of wobble, how can it be prevented, how can it be stopped in such severe cases, and have you heard of any other Mach Ills doing this?

Kenneth R. Wiedenhoeft San Francisco, Calif.

The problem you mention is not, unfortunately, an uncommon one in today’s high-performance motorcycles. Any number of things can cause a high-speed oscillation, and, thankfully, many can be corrected by the average rider who has a basic knowledge of his machine and plenty of patience.

Beginning with the front of the machine, you must make certain that the front forks are adjusted properly at the steering head. If there is too much play in the steering head bearings, a condition as you reported is most likely to develop. The bearings must be tightened down quite tightly, and then backed off slightly until the forks turn freely from side to side, but with no back-and-forth movement.

The next item that should be checked is the swinging arm shaft for excessive side-to-side movement. If tightening the nut on the end of the shaft doesn’t cure the problem, new swinging arm bushings are in order. Because of the loads imposed on these bushings by such a powerful engine as the Kawasaki’s, they should be checked regularly.

Another item that is often overlooked, or more often taken for granted, is wheel alignment. The Kawasaki has reference marks stamped into the swinging arm to aid the rider in adjusting his chain, but they are not always perfectly aligned with respect to the front wheel. Even though the rear chain is running perfectly true with the countershaft and rear wheel sprockets, there is a possibility that the two wheels are not running in alignment. The simplest method of aligning the wheels is by using an ordinary piece of string, stretched along the outside edges of the tires. Make certain that the front wheel is pointing straight ahead, and if possible get somebody to hold the bike upright, off the stand. You might find that the notches don’t quite line up, but unless the swinging arm is bent, you should be pretty close. Increased chain wear will most likely be negligible, and handling will be improved.

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Increased tire pressure is recommended by practically all tire manufacturers for sustained high-speed riding, and you’ll probably find that a couple of extra pounds of pressure in the front tire will make the bike handle better at low speeds. I don’t think that the extra 2-lb. pressure had anything to do with your accident.

The Kawasaki Mach III has a larger percentage of its weight on the rear wheel than do most other large-capacity machines, and 1 have heard similar complaints from other riders regarding oscillations at different speeds. An additional hydraulic steering damper might help matters somewhat, but I’m inclined to believe that there is no certain cure.

OVERGEARED ROAD MACHINES

I recently bought a 19 70 CB 450 Honda, and plan to do some touring this summer. However, the stock gearing bothers me.

At 75 mph the engine turns 6800 rpm. I would like to change the stock gearing so that the engine turns only 6000 rpm at 75 mph.

Maximum torque occurs at 7500 rpm and maximum horsepower at 9700 rpm. Would the change in gearing hurt the performance badly? Also would the change hurt clutch and valve life?

Craig F De Pauw San Francisco, Calif

Most new motorcycles sold for road use come with overall gear ratios that are matched to the capabilities of the engine’s power. Often times raising the gear ratio will put the cruising speed too far below the engine’s torque peak, and necessitate excessive gear shifting to pass or maintain speed against head winds. At 6800 rpm, the Honda 450 is quite comfortable; running the engine at this speed will do no harm, and you will have better throttle response than with the higher gearing.