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Q: My father and I are restoring a Suzuki T20. It’s all going great and we’ve had it running quite nicely. We have noticed that it isn’t charging the battery, though. We removed and checked the rectifier and that seems OK (resistance is only showing one way). We have had an ammeter in line with the battery and you can see the current draw as you turn on the ignition, then more as the lights come on, but when it’s running it doesn’t change. We have a Suzuki Hustler that’s been a temporary parts bike and removed the alternator off that to swap. With them both on the bench we tested the continuity of the coils and found the T20 only had one good pair to the Hustlers’ three! Thinking this was the fault we rebuilt the alternator. Now we can’t get it to run? The lights come on, but there appears to be no spark. We have checked and rechecked the connections, but wondered if you have any advice.
A: The old Haynes manual I’m looking at says the alternator has six coils, wired up in pairs. With the headlight switch off, only one pair of coils is used, for ignition and the brake light. If you turn the headlight switch on, the other two pairs of coils are connected in parallel to the original two for added current capability. From this I’d check to make sure the coils are switched together correctly. If they’re joined in series instead of parallel the output will be different. Find a way to test one pair of coils isolated from the rest of the wiring harness by jumpers to the regulator to see if you get a spark.