There is now no spark on the 1984 ST110.
The only history I have to offer is: The engine was running beautifully, I'd removed the shrouding to paint the parts two days ago. With the dipstick holder off I plugged the oil "hole" oil and started the engine to fine tune the carb. The plug blew out and splattered the oil inside the compartment. I cleaned it up, put the filler tube back, taped it in place with a wad of paper to keep it from hitting the starter gear ring. Started it and it started instantly, ran perfectly at high and low speeds. I removed the battery and started prepping the shrouding, then I removed the brake pads, insured all was right and put it back together.
Today I put the shrouding back on, Put it in neutral, connected the battery and tried starting it but the engine only turned over and it turns out there is no spark. I checked all the electrical connections thinking maybe oil had become a problem in a plug but after removing the ignition switch & seeing there was no oil on it and spraying all the connections with deoxit, there still is no spark.
There is a wire running to the coil which is kept from ground by a phenolic looking spacer, there is a bluish wire coming from the ignition switch which connects to that wire, with a spade lug. There is no 12V voltage to this wire but perhaps that is normal, the junction does short to ground. With the volt-ohm meter I found the body of the coil is shorted with this wire.
There are two wires coming into a plug by the starter. on the mating side of the plug are two power diodes in reverse parallel with the common tip connected to a single wire plug. This plug runs under the starter & into the engine. Both of the diodes appear to be working in that each when tested separately, in place, show a forward voltage and none with the probes reversed.
I'm stymied, I can't figure out what could have happened that there is no spark whatsoever in that I didn't do anything electrical at all while I dealt with the brakes & while paint was drying on the parts on the paper in the garage. Spent 4 hours today trying to get a spark but nothing.
I know there is a safety switch below the seat, maybe another somewhere that is open? There is the 30 amp fuse, are there any others that may be open?
How do I hot-wire it to exclude component failure like the coil or internal wiring?
Edited by KA1J, October 19, 2016 - 06:47 PM.