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SERVICE

JOE MINTON

Smoke signals

I own a 1985 Kawasaki 454 LTD which has two problems that have me stumped. The bike had 5700 miles on it when I bought it and now shows 12,800 miles. Shortly after I purchased it, I noticed a little dark smoke from the right cylinder’s exhaust. I took the bike to my dealer and had the valves and timing chain adjusted, carbs synchronized, and plugs, oil and filter changed. The bike still smoked. I returned it to the dealer and he could find nothing wrong with the bike. The compression on each cylinder was within 10 pounds of each other and the bike ran fine. I have not noticed any excessive oil or coolant loss. The smoke is not that noticeable in day-light, but it’s embarrassing after dark when sitting in traffic and the car lights behind me reflect off of the smoke, making me look as if I’m engulfed in a cloud.

The other problem just occurred recently. The bike runs fine when the engine is cold, but after running for about 15 minutes, it develops a bad miss upon hard acceleration anywhere in the 5000-to-7500-rpm range.

George L. Lewis

Huntington, West Virginia

The symptoms you describe lead me to think that you have two different problems. The smoking is probably due to oil getting into the combustion chamber. On the other hand, the miss is more likely due to a fuel! air mixture problem.

Oil smoke is less noticeable in sunlight than it is when illuminated by headlamps. This is due to the difference in color temperature of the light sources. Smoke from an overly rich fuellair mixture would be more noticeable in daylight and less so at night. If the smoking is worse when the engine is hot and idling (or when coasting with the throttle closed), then the cause is almost certainly oil related. The source of the smoke is most likely poor oil-control ring seal or leaking intake valve-guide oil seals. A compression test will not reveal these problems.

Modern engines generally use lowtension oil-control rings, which will

sometimes fail to seal, especially if the engine is run too gently during breakin. My experience leads me to recommend that you hone the cylinders and replace the piston rings. Break-in should include about 10 full-throttle accelerations from 30 to 60 miles per hour in top gear. This will place pressure on the ring!cylinder interface without creating enough heat to damage either one. It is this pressure and scrubbing effect that will seat the rings. You should also replace the valveguide seals.

Your second problem (the high speed miss) may be due to a clogged air filter. Air filters will become restrictive when they have collected enough dirt. When that happens, the restricted filter will cause the fuellair mixture to become too rich at full throttle and high rpm. It is also possible that the engine is now passing so much oil that it is missing at full throttle. If the miss is due to oil, the bike will leave an obvious wake of blue smoke.

To BB or not to BB

I would appreciate help in finding a source for tapered-roller fork bearings and races for my 1979 Yamaha XS650SF. I would like to change from the stock, old-type BBs that wear out so quickly.

I certainly hate to impose on your vast knowledge of sources, but have no choice. The local Yamaha dealer has the personality of linoleum, and

says there’s no such thing as taperedroller bearings for my 650.

Sam Sherrill Madison, Mississippi

You can get tapered-roller steeringhead bearing sets for your Yamaha XS650. In fact, they are available for most earlier Japanese motorcycles that were originally fitted with loose ball bearings. Your dealer can obtain these from K&L Supply Co., 1040 Richard Ave., San Jose, CA 95050; 408/7276 76 7. K&L does not sell to retail customers.

I strongly recommend tapered-roller steering-head bearings. The loose ball bearings do wear rapidly and that wear can result in a dangerous wobble. A set of tapered bearings will probably last the life of your bike, provided that you lubricate them with light chassis grease and re-apply grease every 20,000 miles or so.

Correct adjustment is critical to the stability of your bike. Set the bearing preload so that the front end is free to turn from side-to-side but does not have any detectable looseness or free play.

I first wrote about replacement tapered-roller steering-head bearings 10 years ago. There have been thousands of sets sold since then. They've been advertised many times. Given that wear is such a problem with ball-type steering bearings, I thought that every service department would know about them by now. 0