Tech Corner

Technical Q and A for classic motorcycle maintenance and repair.

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Keith Fellenstein

BSA diagnosis

Q: I recently purchased a 1968 BSA Firebird Scrambler. It took many tries to finally get it started. When it finally did start, there was a loud backfire through the mufflers. The next kick got it started for good, but it wouldn’t idle down very far. Thinking it was probably stale gasoline, I rode it for a few blocks to check out the clutch, brakes and transmission. All seemed fine, except for a tendency to die when the throttle was released. Long story short, it died right after I returned.

The next day, I tried starting it again. It wouldn’t fire. Thinking it was the battery, which was very weak, I installed a new battery with a full charge. Still, there was no spark at either plug when cranking it with the ignition switch on. I removed the points cover to see if there was anything obvious that would cause this. Much to my surprise, it had an electronic ignition. I don’t know the brand, but I’m guessing it’s a Boyer. Now I’m really stumped. I know it must have been properly installed as the engine did start and run. Where would you suggest I start in diagnosing the problem? For what it’s worth, the white wire to the Zener diode is disconnected. The diode is mounted to the frame under the fuel tank, but the wiring schematic shows the white wire is not used on the 1968 Firebird Scrambler model. The polarity is correct, with a positive ground, unlike many that have been wired incorrectly. Any help you might be able to give will be greatly appreciated. There aren’t any BSA mechanics in my area! —John Botts/Ponca City, Oklahoma

A: You can easily test for spark with a Boyer. First, pull a spark plug and lay it on the cylinder head to ground it. Next, disconnect the trigger wires from the unit under the points plate. With the ignition on, touch the ends together. Every time you touch the trigger wires together you should get a spark. As for the wire to the Zener being disconnected, look around under the tank or seat to see if someone installed a different regulator/rectifier like a Podtronics. If you have one of those installed you disconnect the Zener diode, as the Podtronics device does the work of both the rectifier and the voltage regulator. I’d also check to make sure the rotor under the pickup plate is tight on the camshaft end. If it is loose your timing becomes erratic at best and your bike becomes unstartable at worst. MC


Keith Fellenstein

Hard starter

Q: Why is my 2002 Triumph Bonneville so hard to start? If it has not been started for a few weeks, it is a gorilla to start. The carbs have been re-jetted to a 130 main, a 42 pilot jet, with the needles using two shims. I have replaced the spark plugs and charged the battery. What is the problem? — Rick Romanesque/via email

A:  Your 2002 is different from the old Triumphs I’m used to working on, but since I recently had one the same age through my shop for a similar issue, I’ll take a shot at it. The one I worked on had sat for three years without being run, so the carbs were completely gummed up. But worst of all, and not found the first time, the petcock filters inside the tank had totally disintegrated, allowing all kinds of junk to come back in and clog the just-cleaned carburetors. Once the petcock was replaced and the carburetors cleaned (again), the bike started and ran as it was supposed to. So check your fuel flow through the petcock and the quality of the fuel flowing through the petcock, then make sure that all the carburetor passages are clean, including the fuel enricher/choke. MC


Keith Fellenstein

Cool runnings

Q: I have a problem when checking the cooling level in my coolant tank. I suppose when the bike was new the tank was more or less clear and any color of coolant could be readily seen. Over the years, the plastic has degraded to the point where the coolant is nearly impossible to see. In order to check the coolant level, I have to get down on all fours to view the tank and shake the bike so the coolant can be seen moving. At 70 years of age, this is hard to do. I could simply install a new tank if one is available, but is there anti-freeze out there that is not yellow in color? Any suggestions? — George W. Miller, Jr./via email

A: I have this same problem with a number of plastic containers, from coolant tanks to batteries, and there is no easy fix that I can see. What I do that helps me to see the level is find a way to shine a strong light from behind or beneath the container and let that illuminate the fluid level enough to see. If there is no way to get a flashlight behind the tank, maybe one of those thin, flexible lights can be snaked up behind the tank. Good luck! MC


Keith Fellenstein

Norton luggage rack

Q: I’m trying to find a sissy bar and luggage rack for my 1975 Norton Roadster, to no avail. It could be either of the two or a combination sissy bar/rack. It doesn’t need to carry much weight, either. The items I’d carry are an extra helmet and rain gear. Any suggestions? — Mitch Zyman/Merrick, New York

A: There are a couple of options, one of which we did an article on a couple of years ago. Here’s the link to that one. Also, check out Andover Norton’s website accessories page. Scroll down a bit and you’ll find their luggage racks. MC


Keith Fellenstein

Under pressure

Q: I just bought my first Harley-Davidson, a 1979 Sportster, after years of owning Japanese bikes. Reading the OEM service manual about changing the oil, the manual mentions the possibility of “the oil pump losing prime because of trapped air” after draining the engine oil. “After 1 minute if the oil light doesn’t go out, loosen the oil pressure switch with engine running and let 2-oz drain from the threaded connection.” After speaking to a few Harley mechanics in the area, I’ve been told not to worry about it. I just hate the thought of the engine running for a minute without proper oil pressure, and loosening the oil pressure switch is a chore. Am I making too much of a deal over it? Will the air work its way out by itself? Is there an easier way to remove the air? How about a tee between the oil pressure switch and the oil pump with a petcock? — Ted Chris/Horn, Florida

A: I can’t claim much experience with Harleys, so I’d defer to the actual Harley mechanics and the service manual in this case. You’d be surprised at how little oil is needed to keep the plain bearings happy if the engine is not pulling a load, so even though a minute without oil pressure sounds bad, if you’re not revving the engine it’s probably not as bad in practice as it sounds. MC


Keith Fellenstein

A stuck clutch

Q: I’ve just come back to using my Triumph Silver Jubilee after several months away and it starts just fine, but the engine lurches and stalls when I pull in the clutch and try to put it in first gear? What’s wrong? — Larry Dodd/via email

A: Your clutch plates are stuck together from sitting, and when you pull in the clutch lever to separate them, they don’t. It’s a common problem with old Triumphs, and it has an easy solution. Pull the clutch lever in and use the kickstarter like you were starting the bike. Do this a few times with the key off and the plates should free up quickly. If they don’t, do the same thing but with the key on, starting the bike with the clutch pulled in. That should break them loose if the first method fails. The long term cure is to ride more. Another thing to check if your bike has been sitting is the oil level. Often the oil will end up in the engine sump, which presents problems of its own. It usually only makes it hard to start the engine due to oil drag on the crankshaft flywheel, but in extreme cases, it can force the primary oil seal out of its seat. That’s not a problem on your bike, as the primary side isn’t a separate oil bath; it shares engine oil and ventilation with the crankcase. Once you have the bike started, it’s a good idea to open the oil filler cap and make sure you have good oil return to the tank. I usually briefly close the return pipe with my fingers to force a little oil into the rocker arms. Don’t rev the engine any more than necessary to keep it running until the return side of the oil pump has had enough time to empty out the sump. This usually takes a couple of minutes, at most. You can ride it, just don’t give it the beans until the sump clears. MC


Keith Fellenstein

Shifting issues

Q: I own a Norton Atlas with a single carburetor and magneto ignition. Lately, when I shift from first gear to second, it goes into second and then as I open the throttle it jumps into neutral. When I press down on the shift lever again it will go into second gear. I should also mention that I am having some clutch issues. The lever pull is very hard and the gearbox is a bit loud when shifting gears. What should I check first? — Mike LeBlanc/Moncton, New Brunswick, Canada

A: My first guess would be worn gear dogs causing your bike to jump out of second gear, but if it stays put when you push down on the lever it may be that the shift plunger that holds the gear cam in place is not doing its job. If it has been a few years since the gearbox has been renewed, now would be a good time to pull the guts out of the gearbox and inspect all the components for wear. Gear dogs get rounded off over time, bushings wear and mainshaft and countershaft bearings wear, too. The plunger that holds the shift quadrant in place gets rounded off and doesn’t provide a positive lock between gears. Bringing the gearbox back to specifications should give you more precise and steady gear changes. MC

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