Technical Q and A for classic motorcycle maintenance and repair.
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 your subject.
1973 Triumph Trident Consistent Starting Problems
Q: Keith, I have a 1973 Triumph Trident. I am having a problem with consistent starting. I have tried tickling each carburetor and keeping the battery on full charge. It has a Boyer ignition. I have been told that the early Boyer ignitions for Tridents would sometimes fire erratically, causing problems. Does the position of the main jet in the Amal carb have any bearing on the problem? - Joe Worthy/via email
A: The Boyer electronic ignition is pretty reliable, but well-known for being sensitive to voltage. If your battery voltage is low, the black box sets the ignition to full advance. Since you keep your battery charged we can discount this possibility. That leaves timing and carburetion as the variables. Since timing is a lot easier and less messy than the carburetors, let’s start there. You’ll need a timing light for this, and for best results an extra battery to power the timing light. Since the Boyer is a wasted spark system, it doesn’t matter which plug lead you use to attach the timing light. I use the one closest to the viewport on the right side of the engine. Take the top two screws out of the Triumph Trident patent plate and loosen the bottom screw to let the plate rotate down. Notice the bottom screw is longer and has a point at the end. This points to the timing mark at the proper rpm. Start the bike (with difficulty, probably) and rev the engine to about 3,000rpm. At that speed the B mark on the alternator rotor should line up with the pointer. If it doesn’t, you’ll have to adjust the timing using the pickup plate under the points cover. The auto advance unit, or in this case the rotor magnets, move clockwise. To retard the spark you would move the pickup plate in the same direction as the rotor magnets, clockwise. To advance the spark you would move the pickup plate in the opposite direction as the rotor, counterclockwise. The main jet should not have any bearing on starting; it’s usually the idle circuit that’s the problem. The Amal Concentric carburetors are notorious for clogging their idle circuit, making starting difficult. You’ll have to dismount the three carburetors to clean them properly. Once the carbs are off the bike, clean them. Once the carbs are off the bike, read Amal Concentric Carburetor Overhaul on cleaning Amal Concentric carburetors. MC