VT700 ignition issues

[shadowbob84]

Ok, first official post. I bought a 1984 vt700 for a couple hundred bucks a few weeks back. Didn't run, but the engine turned over when we jumped the starter so I figured it would be fixable. I bought the bike as a bobber project and most wires were removed the first week with the help of my trusty Clymer wiring diagram so I wouldn't remove anything vital (ignition, pulse generators, alternator, etc.). When we decided to put power to the old girl there was no spark. I tested the coils/wires and they were OK. Then I tested the pulse generator resistance. One had 420 ohms and the other was about 400. It was a little chilly (maybe 50 F) so I thought maybe the lower resistance was an effect of that. One question I have is: should there be battery voltage supplied to one of the coils? We tried this by splicing in a wire to the front cylinder coil. This gave a weak spark to the rear cylinder, but still no spark on the front. Next we swapped the spark boxes from one side to the other. Still had spark in rear, but none in the front again, so my spark boxes seem to be OK. I'm stumped at this point and any advice or encouragement would be appreciated. Any and all criticism will be tossed by the wayside.

Andy

[bpratt18]

I'd start with the simple stuff first. Did you replace the boots that clip onto the spark plugs? If it's an old bike, and they're the original ones, that could possibly be the issue. You can get them at your shop for a few bucks. You said you had to jump the starter, is the start switch not working? I was running through some electrical problems and I got a lot of advice directing me to look for a faulty ground somewhere, so I'd look for that too. Good luck, and congrats on the purchase, they're fun bikes!

[shadowbob84]

Didn't replace the boots, but resistance was within the limits that the manual provided.

[tubes_rock]

If I recall how those ignition boxes are wired, they control the spark by turning the ground to the coils on and off. I believe you'll find 12 volts on the coils all the time.

--Justin

[shadowbob84]

That sounds promising. Has anyone ever attempted a rebuild of the pulse generator(s)? With only used parts available and even those are expensive I may try this myself.