Originally Posted by
SoFarKingSlow
Thanks for the reply. It would run for a second or two and I would get a hot spark for a second or two. I agree that a bad ground is a likely culprit. I had the bike completely disassembled and changed the battery, key switch, coil, starter relay, piston and rings...so there was lots of things that had been unplugged and messed with. I ohmed all the grounds, as well as the coil and pulser and stator. I even pulled the left case off to make sure the pulse looked good and that water hadn't snuck in. The only thing left was the CDI. I didn't think it was likely because the trike was supposedly running before it sat for a decade. CDIs that plug into the 1985 250SX are really hard to find and really expensive. I got a cheap one from Ebay and spliced the new style connector to the old bike. There is a great thread by ps2fixer with a pinout chart for multiple years. After all that I got no spark... I happen to have a junk 1994 TRX250 and I tried that as a shot in the dark. It fired right up and ran like a champ.
Lesson learned: CDIs go bad.