[technicalities]

[TECHNICALITIES]

GORDON H. JENNINGS

NOTHING brings quite so much anguished uncertainty into a motorcyclist’s life as the process of breaking in a new bike, or a rebuilt engine. If one follows the book, the business takes forever; and if one does not, there is the nagging thought that the machine may be ruined forever.

Actually, I do not believe in “breakingin” a motorcycle at all — or at least, not in the usual way. When you get right down to the bare essentials, the prolonged breakin should not be necessary. If the manufacturer has made the machine to correct tolerances, only the piston rings will require any bedding in at all, and this process can be completed within no more than 20 miles. In fact, if the rings are not seated within 20 miles, they will very likely not seat at all until perhaps the 2000-mile mark. Slow, gentle running will not seat the rings. The job can only be done correctly by giving the engine short bursts of full throttle, followed by coasting with the throttle closed. The full throttle bursts will create enough gas pressure to force the rings out hard against the cylinder walls, and bed them in before the cylinder has a chance to glaze; and the coasting with the throttle closed will pull oil up past the rings to

lubricate the upper cylinder. The fullthrottle/coasting process should be repeated about a half-dozen times.

Apart from the rings, there should be no need for “running-in” anything. No modern bearing (either ball, roller, needle-roller or plain-metal) requires any wearing-in, and modern seals, if they are not installed “dry” will do whatever sealing job they are capable of right from the first turn of the shaft.

The only parts in an engine that might benefit from a long break-in are the pistons. In any touring-type engine these are installed rather tight, to stop piston-slap when the engine is cold. Indeed, some have so little clearance when cold that they are virtually a press-fit in the cylinder when hot, with only the film of oil on the piston skirt preventing metal to metal contact. Obviously, any high spots will tend to gall against the cylinder wall, and if this galling is really severe, the cylinder will “pick-up” bits of aluminum from the piston. If this occurs, you may as well strip the engine and rebore, because once a bit of aluminum becomes embedded in the cylinder wall, it will continue to pick up other bits from the piston and the piston will very quickly become badly scored.

The other place where a break-in will do some good is in the brakes. Rarely will a new lining make full contact with the drum; instead, you will find that there are high spots that make all of the initial contact and only after the lining has worn enough to remove these high spots will you get full contact. Now this would create no problem except for the fact that hard braking when the linings are new will con-

siderably overheat the high spots and cause them to glaze over. The glaze that forms, being relatively hard and slick, will not wear away for some time, and while it is there, you will not get much performance from the brakes. Moreover, because the brakes will then require so much pressure to deliver any stopping power, more glazing will form as the high spots wear slowly away and the end result is that the brakes will never quite be right until the linings are replaced — after which the average rider will do the same thing all over again.

Obviously, you will have to use the brakes to bed them in, but hard braking from high speed must be avoided. All things considered, it is probably best to find some lightly-traveled road and spend some time in repeatedly braking from, say, 50 mph down to 10 mph. Give the brakes a rest periodically, to cool them. After an hour of this, the brakes should be bedded sufficiently for normal traffic, but they should not be used really hard until 250 to 1000 miles have been traveled — depending on the brake lining.

So, seen in this light, the break-in period is actually a time for bedding in brake linings and smoothing high-spots from pistons, and there are better ways of doing both than simply riding slowly for 1000 miles. Brake bedding-in I have explained (or at least my own system); piston breakin I hasten by running the engine quite fast, but at a relatively light throttle. The important thing to remember here is that it is piston expansion that will cause trouble, and piston expansion is a function of heat. Heat, in turn, is related to throttle, and you will do far more damage running up a long grade at 50 mph under full throttle than can be done whistling down the other side of the mountain at 70 mph with half to 3/4ths throttle applied. Therefore, you may feel safe in turning the engine fairly briskly, but throttle openings should be very light initially (except for the bursts needed to seat the rings) and increased gradually as miles accumulate. There is no fixed rule as to the rate of increase; it varies from make to make, and even between different examples of the same make and model. Some sensitivity on the part of the rider is required, if only enough to perceive that a tight engine stops with a thump; where one that has its pistons at the correct tolerances coasts to a halt more gradually.

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I feel reasonably confident in predicting that it is only a matter of time before motorcycles will follow automobiles in the abandonment of any break-in period. Many, if not most manufacturers give no break-in instructions beyond simply cautioning against long periods of full-throttle, full-speed running for the first thousand or so miles. Racing engines, of course, require no running-in, and I rather expect that the 3 to 6 miles one finds showing on the odometer of a new motorcycle includes some distance devoted to bedding-in rings for the customer. I suppose it is still best to follow the owners manual’s recommendations regarding those first miles, if for no other reason than that it gives you an arguing point should anything go wrong. However, I do think that most motorcycles would get on very well without manualprescribed break-in procedure. It seems to me far more important to re-torque head bolts, set valve clearances, etc., after things inside the engine have had a chance to settle. Also, that first oil change is exceedingly important, because the first oil supply the engine gets will very quickly gather up micro-particles of metal buffed from the rings and cylinder walls as the rings bed-in, and there may be some grit assembled into the engine.

IN OUR March, 1965 issue of CYCLE WORLD I held forth at length on the subject of road-racing leathers, and as always when I do things like that some sort of trouble follows. It seems that I completely overlooked Langlitz Leathers, which was not a good thing to do as they will make lightweight, tight-fitting leathers to order — indeed, all of their leathers are custom tailored and you can ask for (and get) anything you like. Langlitz’ order blank includes a very complete measurement chart, and there is little doubt that they can make them to fit. There is even a measurement for crotch-to-neck length up the back while seated. For road racing I would suggest that anyone ordering leathers from Langlitz also give the same dimension, because the extreme crouch adopted in road racing will leave you with too much material in the front of the suit. I would also recommend a nylon lining in the areas of elbows, knees and hips, as the nylon is slippery and will prevent skin “burns” inside the leathers. It is possible to get scuffed quite severely without tearing the leathers, as the leathers will momentarily “stick” to the pavement when you hit, and your skin keeps moving inside. A small patch of nylon cloth will minimize the damage.

In any case, my apologies to Langlitz, and to the two different chaps (who were wearing Langlitz leathers) at my last road race who told me what a jerk I was to have overlooked the obvious. Perhaps I should stick to my slide-rule and forget about the fall fashions.

RECENTLY, WHILE FLOGGING a motorcycle hard, it occurred to me that one of the instruments that would be useful on a motorcycle is an oil temperature gauge. This is a standard fixture on most highperformance air-cooled engines, and it does give one a good index of heat level in the engine. A cylinder head temperature gauge would be a good thing too, but I have not seen that used on a motorcycle either.