The Service Dept
THE SERVICE DEPT
JODY NICHOLAS
MORNING OILER
I have a 1965 BSA 250 which is really giving me a headache. When / start it up in the morning, it belches clouds of blue smoke out the exhaust pipe. This smoking continues for a couple of minutes, and then stops.
If I start the bike every two or three days, it doesn’t smoke, but if I let it sit for a week or so, it smokes. Do you have any suggestions?
Robert Bailey Miami, Fla.
This condition is most often caused when the non-return valve on the feed side of the oil supply sticks open, allowing oil to drain past it into the crankcase.
The non-return valve on your ma-
chine is located under the large nut on the right-hand side of the crankcase at the front. Remove the nut and you will find a spring and, at the other end, a ball bearing. This ball bearing fits into a seat which must be smooth in order to shut off the oil supply when the engine isn't running.
When the engine is started, engine oil pressure causes the spring to compress slightly, allowing the ball to lift off its seat. If the spring becomes weak or corroded, incomplete sealing will result and the crankcase will become filled with oil, which causes the smoking. If in doubt, replace both the spring and the ball.
SILENCE IS GOLDEN
/ have a 1970 BSA 650 Thunderbolt. / wish to put a set of megaphones on it and run the megaphones with the tips on, but with the baffles out. What size main jet should 1 replace the stock main jet with? Is there any danger of damaging the valves, pistons, etc? 'The bike is completely stock.
Mike Wilke Montgomery, Ala.
Installing a set of megaphones with the baffles removed would be one of the worst things you could do to your machine. Not only would your low and mid-range acceleration suffer because of
the reduction in exhaust back pressure, but the increase in exhaust noise would bring your presence to the attention of the populace and the police, and would make you popular with neither!
The motorcyclist is just now becoming an accepted part of our society, but one man with a noisy machine can undo the work of 10 riders with quiet, legal machines. It’s the kind of exposure we don’t need.
BALANCE FACTOR
I would like you to answer this question / have about my 1967 Norton Atlas. I am going to balance my crank (have it done, actually) after getting the cylinders bored 0.010 oversized. Ij l change the Atlas balance factor oj 84 percent to that of the Commando's 52 percent, will vibrations be reduced at any point in the rpm range? I realize the Featherbed frame doesn't help the situation much.
Beter McGowan San Francisco, Calif.
The balance factor used in any motorcycle engine is largely determined by the method of mounting it in the frame, as well as by the design of the frame itself.
A vertical twin engine, like a Single, is very difficult to balance, and a large capacity, long-stroke unit like the Norton Atlas is even more difficult. In fact, one of the main reasons for the design of the new Commando was to help alleviate most of the Atlas’ heavy vibration.
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In this respect, Norton has been very successful. Except for a period of heavy vibration below 2000 rpm, the Commando is one of the smoothest large capacity machines available. This vibration at low engine speeds is successfully damped by the Isolastic engine mountings, as is the vibration higher up in the rpm range.
Changing the balance factor of your Atlas crank to that of the Commando would most probably result in such a “shaker” that it would be very uncomfortable to ride, and difficult to keep the accessories bolted on. The balance factor was carefully worked out by extensive testing at the factory, and I seriously doubt that it could be improved upon very much.
After having your machine bored, take the crankshaft, connecting rods and complete piston assemblies to the balancing shop and have it checked and, if necessary, rebalanced to the factory’s specifications.
AN OIL COOLER?
I will be buying a large Twin shortly (probably a Norton or Triumph), and it would seem to me that the nicest thing I could do for my engine would be to install an oil cooler.
A question remains in my mind, though, as it seems that this might upset the manufacturer’s scheduled tolerances and expansion rates.
The bike would be subject only to occasional winding road enthusiasm and two-up touring. It can expect loving care, not stoplight racing.
Bill Rogers Fallon, Nev.
Oil coolers are becoming increasingly popular on both racing and road machines. Several accessory manufacturers are now marketing them at reasonable prices, and the installation on a machine such as you are considering is a relatively easy job.
When riding double on long, high speed trips in the summer, it’s conceivable that the oil’s temperature could reach an unsafe level. As you probably know, the BSA and Triumph three-cylinder machines come equipped with an oil cooler, which should tell us something!
We did some research on the subject beforethe article “Oil and the FourStroke” appeared in the Jan. ’71 issue of CYCLE WORLD, and found that the hottest we could get our Honda CB750’s oil to run was 230 degrees F, which is less than Honda’s recommended maximum of 244 degrees F. This reading was obtained at freeway speeds with an ambient air temperature of 100 degrees, but without the use of an oil cooler.
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I’m under the impression that a vertical Twin runs somewhat hotter than the Honda Four, and that high speeds in the summer could raise the oil temperature to an unsafe level. The addition of an oil cooler couldn’t do your machine any harm, unless you run it in very cold weather without blanking it off, which would keep the oil from getting up to operating temperature.
WHEEL ALIGNMENT
/ am in urgent need of information on wheel alignment. On a Honda CB450 '68 model, there is a spacer normally installed on the right-hand side of the front wheel. This spacer is approximately 'A in. thick. If the axle is turned around and the spacer is installed on the left-hand side:
What effect would it have, going down a straight road7
What effect would it have, going into a right-hand curve?
What effect would it have, going into a left-hand curve?
Would the effect be predictible?
Would the effect be dangerous?
George C. Mennecke St dwell, Okla.
Ideally, the back wheel of a motorcycle should have its centerline directly behind the centerline of the front wheel. Although most motorcycles are designed this way, there is one notable exception. The 1967 BSA 650 models were altered from previous models by changing the 0-degree tilt aspect (in the vertical plane) of the front wheel. This was done because the machines had more weight on the left-hand side of the motorcycle due to the clutch, primary chain and alternator. When the rider let go of the handlebars, pre-1967 models had a tendency to turn left, and changing the vertical aspect of the front wheel (tilting it slightly to one side by slightly offsetting and boring the axle holes) tended to balance out the machine’s inherent imbalance, and reduce the tendency to pull to one side.
Switching the Honda’s axle and spacer from the right to the left side would, of course, offset the front wheel VA in. to the right. 1 can’t understand why anyone would want to do such a thing on purpose, but if the axle and spacer were incorrectly installed, I don’t think the handling characteristics would be altered drastically. In fact, a person not familiar with the handling characteristics ot the CB450 might not be aware that there was anything wrong at ali.
I would recommend that you leave the spacer on the right-hand side and not be anxious to experiment with what the designers had in mind. They were pretty close!
CABLE REPAIR
/ own a 1968 BSA 650 Twin and am having some control cable problems l hope you can help me with. Original replacement cables are very rare and expensive around here, and since I can get all the parts l need, I would like to make my own. The trouble is that I can't get the ends to stay on the clutch and front brake cables. Idease tell me the correct way to fasten the ends to the cables.
Scott Foster Knoxville, Tenn.
Most cable ends are supplied with one end of the hole going through them slightly countersunk. This is to allow the inner cable to be unbraided and spread slightly, and also to allow a place where the solder can collect.
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When placing the end on a cable, the inner cable should be perfectly clean and free from oil. Thread the inner cable through the small section of the replacement end, cut it off just slightly longer than you want it, and spread apart the wires of the inside cable.
Dip the inner cable in a bottle of tinner’s fluid momentarily, to aid the flow of solder, and use a soldering iron (not a propane torch or other flame which might make the cable brittle) to heat the new cable end. The solder should flow into the countersunk hole without having to touch the solder to the iron.
Be sure to use acid core solder, and when the solder has cooled, use a file to remove the excess material and any strands of the inner cable that may be sticking out past the edge of the new cable end. If you have made a good solder joint, and if you keep the cable well lubricated, it should last you a long time. föl
