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1974 Triumph Trident Troubles

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Trident troubles

Q: I recently bought a 1974 Triumph Trident T150V, which I have had no
problems with up until a week ago. Returning home from a run it began missing
at 3,000rpm through all the gears. Initially I thought it had sucked in
moisture through the air cleaner when I got caught in a major downpour of rain.
I limped home, cleaned and dried the air filter, and replaced the spark plugs
for good measure, but this did not rectify the problem. It didn’t have any
problems starting, but as soon as the engine hit 3,000rpm it once again began
running rough. Then, without warning, the engine completely cut out and has not
sounded like it even wants to fire since. I unhooked each lead, inserted a spare
spark plug and cranked the bike over, but there is no spark at the plug across
any of the cylinders. I presume I have a coil, Boyer ignition or battery
problem but do not know how to test these components in order to isolate the
source of the problem. I would be appreciative if you would be able to shed
light on my current predicament. — Kere Cookson-Ua/via
email

A: There are
several ways to test all these components, so let’s start from the simple and
move on to complex. Boyers can be sensitive to voltage, so make sure your
battery is up to snuff. Turn the headlight on and make sure it stays bright for
at least a minute. If you have a multimeter you can check the voltage. It
should stay at about 12 volts for that time. Then make sure you are getting
power to the Boyer ignition. The kill switch on the handlebars is known to get
corroded and stop the bike from running. In addition, the ignition switch can
get corroded, too. I’m assuming you still have a positive ground electrical
system. Make sure you have a good ground, both from the battery to the frame
and from the Boyer. Try running a wire directly from the negative side of the
battery to the white lead on the Boyer. Check for spark as you did before. Any
luck? You’ve already tried the cranking test with a spare spark plug, so we’ll
move on to a test that bypasses the pickup coils. Disconnect the two wires that
go to the stator plate on the timing side. Pull all three plugs on your Trident
or pull the plug wires and use new plugs in the sockets. Ground all the plugs
to the engine. Turn the key on, then touch the two leads from the Boyer box
together. If you have a spark at all three plugs then the pickup plate is
faulty. Sometimes, due to vibration, the wires will fracture inside their
insulation on the plate. If you don’t get a spark, it could be that you have a
bad coil. Since the coils are in series, one bad coil can keep the rest from
working. Try bypassing all but one coil and repeat the previous test. Do that
for each coil. Did you get a spark? If you did, one or more of your coils is
bad. If you get no spark after trying all the coils, you probably have a bad
Boyer ignition. The only way to test the black box is to substitute a known
good one in it’s place. I’m betting you find the problem is in the ignition
switch or the kill switch. MC 

Published on Aug 6, 2013

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