Bad misfire
Bit of a puzzle to me, this one. The XT has been laid up for 3-4 weeks while I got the stuff to rebuild the rear wheel. Sunday I got it all together and had a successful test ride. Monday I set off to work and at the first junction it backfires and dies. I assumed it was running out of fuel, switched to reserve, restarted, and refilled at the next opportunity. Work and back, all fine. Tuesday, work and back (25 miles) all OK. This morning, it seemed fine until I switched on the headlight in a bit of drizzle. Within half a mile it had started misfiring, backfiring and losing power big time. I switched my route to side roads away from the traffic and it stalled. It restarted fine, and idled away like nothing was wrong, but when I got going it could barely pull 20 mph in 2nd, with a really bad misfire and a lot of banging from the exhaust. It had no problem idling, but as soon as it was asked to do work it misfired badly. I was about to head for home when I decided to turn off the headlight. Within a few seconds the misfire cleared and it ran like a good'un, and I decided to head for work again. It got me there with no further problem - another 6-7 miles with the headlight off.
My first thought was a blocked jet, but the fact that reducing the electrical load seems to have corrected it makes me think it's electrical. But what? There's plenty of juice in the battery to start it, so it's not a dead battery. But I can't think of any way that turning on the headlight should make this happen. Anyone got an idea?
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