The Service Dept

THE SERVICE DEPT

JODY NICHOLAS

WHAT'S A LITTLE OIL?

I have a 1971 Honda K1 750 and have gotten conflicting answers on two questions. Maybe you could set me straight.

First, while riding two up, I noticed that the bike was burning oil when I would accelerate. This happened at highway speeds (60-70 mph). One person told me this was normal and another said I was going to have problems and this was a warning signal. What do you think?

Second, what is the story on the four-into-one exhaust systems for this bike? Some claim to increase your performance and horsepower, yet I have heard that all they are good for is to give you room to mount saddlebags and improve appearance.

Dan Streeter Tucson, Ariz.

Depending on certain conditions such as the mileage of your machine, the care it has received and the manner in which you ride it, the oil consumption should vary between a half and one full quart between oil changes, or about every 2000 miles.

After riding down the highway for a time at 60-70 mph, it is common to see some light blue exhaust smoke when the throttle is opened. It must also be remembered that some brands of oil emit more visible smoke when burned than others.

I would say that if your oil consumption is in the region of 1000 to 2000 miles per quart, you have nothing to worry about unless the engine is unusually noisy.

It is quite possible for a well-designed four-into-one exhaust system to increase the engine’s power marginally at some point in the rpm range. Another appreciated plus factor is, like you mentioned, more room to mount saddlebags, and a reduction in weight over the standard system using the four separate exhaust header pipes and mufflers.

A Siamesed exhaust system is inherently quieter than four separate pipes, but Honda has been working on the problem of noise pollution. The latest CB750 K2-series machines are quieter than the K1-series machines, and they were somewhat quieter than the first CB 750’s. This reduction in noise has been achieved by changes to the baffles inside the mufflers.

One advantage of a four-into-one exhaust system is that it runs hotter in the muffler than a four-pipe system. This extra heat helps reduce the condensation of water and acids inside, which could cause the muffler to rust out.

BREAK IT IN!

Two friends and I were having a discussion and developed three different opinions on the subject of breaking a motor in. Fm sure this would be important information for every motorcycle owner, and car owner for that matter, who’s concerned with the welfare of his engine.

One person says that break-in is unnecessary. All you need to do is change the oil on a four stroke. The other extreme is a long, slow, low throttle break-in. We would like to know why a break-in is necessary, or if it is. Also, what happens during the break-in? Your experience will be appreciated.

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The Tri-Power Menlo Park, Calif.

If a break-in period wasn’t beneficial to the life of a motorcycle, the various manufacturers wouldn't spend the extra money necessary to notify owners in instruction manuals and on the motorcycles themselves, would they? Breaking-in, or running-in, as the British say, is the most important portion of an engine’s life. The method used and distance covered during the break-in period varies according to the type of machine you’re talking about and the use to which it will be put.

Quoting from a recent model BSA twin-cylinder instruction manual: “Running-in should commence at one-third to half-throttle, and for the first 500 miles the speeds should not exceed those given on the ‘running-in’ label. Thereafter the throttle opening may be progressively increased as the mileage builds up, until at the end of the running-in period full throttle can be employed.

“If excessive speeds are used in the early stages, there is risk of seizure and other troubles, and in any case, until the machine has been properly run-in, it cannot be expected to give its best performance.

“Smooth throttle control and selection of the correct gear for the prevailing conditions will ease the work of the engine. In particular, avoid violent acceleration, and do not allow the engine to labor on hills in a high gear, when a change to a lower gear would ease the load. This ensures that all parts of the machine are properly run-in and are quite free.”

Breaking-in a machine is, of course, up to the rider. He can shorten or lengthen the life of his bike depending on how he treats it in its early life.

I recommend following the manufacturer’s suggestions for breaking-in a motorcycle, and for any internal combustion engine-powered vehicle for that matter. You see, an engine is made up of many closely fitting parts and bearing surfaces. If these parts are helped along during their mating process with adjacent parts, the surfaces will develop smoothly and friction, which is a major cause of heat, will be reduced.

Breaking-in a two-cycle engine is somewhat simpler and usually a shorter process than breaking-in a four-cycle engine because of the reduced complexity and number of moving parts. But in either case, it is a particularly good idea to let the engine warm up until it approaches its normal operating temperature before riding it hard.

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A four-stroke is more easily damaged if this precaution is overlooked. This is because a four-stroke relies on a film of oil to cushion the plain bearings often found between the connecting rods and the crankshaft, and to a lesser extent the camshaft and transmission bushes.

On either type of engine, the piston is the first moving part of the engine to heat up, and since it will expand more rapidly than the cylinder itself, it should be obvious why a warm-up is beneficial.

The reasons for breaking-in are many and valid. I believe in them.

THEY'RE THE SAME!

/ have a 1970 SI.350 which has the standard 33 blip 1970 engine. In 1971 this engine was changed to produce only 25 blip but lots more torque at lower rpm. I would like to convert my 1970 engine to 1971 specifications as low end torque is much more desirable to me than peak horsepower. Can you tell me what parts I will need to convert my 1970 engine?

Arnold Betbeze Soddy, Tenu.

You are mistaken in believing that there is such a difference in the maximum horsepower and amount of lowspeed torque between the 1970 and

1971 SL350 model Hondas. The power producing parts of the engines are identical.

However, the 1971 SL350 has slightly different internal gearbox ratios and the suspension system has been modified somewhat. Otherwise the two machines are identical. [ñl