Technical Q and A for classic motorcycle maintenance and repair.
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Q: I just bought a 1974 Triumph Trident T150. It’s very clean and has been in storage since 1988. It had 5,925 miles when I bought it. It has a Boyer ignition and I had it running well; it would start in two to three kicks. Recently, I rode it about 20 miles at 55-60mph, and as I was getting close to my destination it was losing power and seemed to be pinging. On my return trip, after about five miles it really started to lose power and ping, and at a stop I had smoke from the left side and it seemed really hot. I pulled the plugs when I got home and they were in good shape, but seemed loose. Now I can’t kick start the bike. If I bump start it it will run, but it quickly begins to lose power and pings. Do I need to decarbonize it or should I overhaul the top end? - Ken Rowan/via email
A: I had a similar problem with my Trident a couple of years ago. I thought I had the timing set perfectly, and went out for a ride. Everything went well for about seven miles, then I started losing power and the engine started pinging. I limped home and checked the plugs to find the two outer plugs were showing they had been running extremely hot and the middle plug had burned the center electrode down to the ceramic. I double-checked the timing only to find it was severely advanced. I put in new plugs (after making sure I hadn’t burned a hole through any of the pistons), and immediately reset the timing to the correct advance. This was shortly after I installed an electronic ignition, and all I can think is that I didn’t have the rotor tight enough on the timing cam. I haven’t had any trouble with it since.
In your case, the first thing I would check would be the timing. With a Boyer, battery condition is important, so make sure your battery is fully charged. Check the timing after the engine has been off for a while; the timing case fills up with oil as the engine runs, and after a few minutes oil will start to come out of the hole where you view the timing marks. The timing marks are behind the Triumph patent plate on the right-hand side of the engine. You unscrew the two top screws and slightly loosen the bottom screw. When you push the patent plate aside, you’ll notice that the bottom screw is longer and comes to a point. This is the pointer that lines up with the timing marks when the engine is running. For best results, hook your timing light to a separate 12-volt battery, not the battery of the bike you are timing. This keeps any voltage fluctuations in the power supply from affecting the timing strobe. Clip the trigger probe to the right most plug lead and start the engine. Throttle the engine up to 3,000rpm. Using the strobe, observe the pointer in the timing case and the timing line on the alternator rotor. There are two lines scribed into the alternator rotor, A and B. The B line should line up at 3,000rpm. If it doesn’t, you will have to adjust the timing by moving the pickup plate mounted inside the points cover, up and to the right of the timing mark inspection hole. Moving the pickup plate counterclockwise will advance the timing, and clockwise will retard it. MC