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Troubleshoot Ignition Problem

Barry

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Montreal, Quebec, Canada
Howdy y'all,
I'm looking for help finding a fault in my ignition system on my 1984 Nighthawk 750S.

Brief history of bike:
A couple of summers ago I bought it through Craigs.Bike ran pretty good. Idled a little rough. There was an intermittent skip to the firing cycle, and I had to play with idle set screw to keep it running (turn it up when cold, back down when hot). Overall, it got me around, though I felt it was low on power.

This summer I decided to do a thorough carb job. Bought an ultra sonic bath. Cleaned carbs.
Put them back on bike, fired it up. Bike literally ROARS to life. A completely different beast from before. But despite the apparent liveliness of the engine, the aforementioned skip was happening with every cycle, rather than every few cycles. I checked the exhaust pipes. #4 remained stone cold. Using an induction timing light, I get strobe on all four cylinders.

Then I have to do some renovations around the house for a month. No time for bike until this week, and now I'm incredibly frustrated. The bike will not even cough or sputter. It cranks just fine, but that is all. The exhaust stinks of gas, the spark plugs are wet with gas.
When I try my induction light, it does not light up on #1 or #4, and is very inconsistent with #2 and #3.
It has been raining like crazy the past month, but the bike is under a carport, so while damp, not getting directly hosed.
I'm figuring there could be a short somewhere, but I'm not sure how to go about pinpointing it.
I've applied the very scientific method of wiggling all the wires. No effect.

I used a multimeter to check the coils. They are both within spec.
Then, this is where I begin to get confused. Here's what I've done:

Connect meter between leads on first coil (#1, #4), turn ignition switch to 'start' position. Meter jumps to 9.5 volts, then drops to 0 within 3 seconds. I thought this should be 12 volts, and don't know what to think about the drop. I can repeat this consistently.

Connect the meter to leads on 2nd coil. With ignition on, meter jumps to and remains at 9.5 volts for as long as the switch is on.

I move to the spark unit. Check pulse generators. They are within spec.
I decouple the wires leading to the spark unit, check input voltage there. It measures 12.something.
I obtain a second spark unit (from a scrapyard), plug it in, no effect on my measurements.

And so here I am stuck. It's like 12 volts go into the spark unit, but only 9.5 come out, why the voltage drop on circuit to the first coil?

I don't know what to check next. Any suggestions?
thanks
B
 
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