Motorcycle Repair: 1983 NightHawk - Starting issue, regulator rectifier, exhaust pipes

Question
Hi Chris
I purchased my Nighthawk and have been restoring it for the last 7 months, it’s all done, it runs great, but now I have an issue.

I can get the bike started first thing in the morning, like I usually do. Open the choke, turn the key on and press the start button. It starts just fine, but within a few seconds it starts running rough and the RPMs start dropping, if I try to twist the throttle it stops, if I don’t touch the throttle it still dies within a few seconds.
The problem is that I cannot get it started after that, if I try it within 30 minutes or more later it starts fine and runs great the rest of the day, including starting numerous times during the day.

Not sure if the colder weather (I’m in Japan) over night around the mid 30’s has anything to with it.

It has a fully charged battery that is about 6 months old, a new Regulator which I have tested and it’s putting out about 13.5 – 14 volts. I have checked the connections from the stator, the regulator/rectifier, CDI, Pulse generator, ignition coils and starter coil. Not sure what I should test, and when to test it.

Also I have checked for gas in the bowels by opening the draining screw, and there’s plenty of fuel in there.

The vacuum hose from intake 2 to the fuel cock is connected, I have a full thank, fresh oil and filter, the plugs are 7 months old with only about 2500 miles on them. They are not fouled, when I pull them out, they are of a light cream color, very clean.

Like I said, once I wait at least 30 minutes or more after it quits from the first start up of the day, it starts fine and runs great for the rest of the day.
What so you suggest I check or do first.

Any suggestions are very much appreciated

Thank you
Mario


Answer
Hi Mario.

 Did you do (or have done) a complete disassembly cleaning of the carbs?

 Have you checked to make sure that the exhaust pipes are seated and tightened down correctly to the heads?

 How about the timing and valve adjustment?  Are those set correctly?

 Mostly, it seems like the bike is starving out.  This could be a mixture issue.  If the caps over the mixture screws have been removed, then the mixture has been changed.  If you cannot get the mixture right through adjustment, you may need to replace the carbs with fresh from the factory, new ones.

Let me now what you find.
Good luck and ride safe.
FALCON