Motorcycle Repair: GL400, vacuum leak, intents and purposes

Question
Hi Bill.
I just came across the site in an effort to help a friend rebuliing a Jap import GL400, which is for all intents and purposes a 400cc CX custom, not sure if you ever had any dealings with any of the models beofre.Nobody else, my self included has. Basically he has 2 problems I can see.
One : bike runs well (sweet as can be) for about a K then dies.
Two : It has blown a few sets of (used)plugs
(blown totally open circuit !)
Re: 2 the plugs he is using  D8EA's should he be using D8REA's ?  plugs look a little sotty (may be as a result of problem 1)
Re: 1 we Suspect
dodgey diaphrams and maybe also mis-adjusted slow jets.
We have by passed the tank using a container with a 6mm bore  hose,it fills the bowls as fast as the floats allow)
It has fuel in bowls when it konks out.
If you could shed any light on the subject I would be very greatfull

Cheers
Greg

Answer
Greg, Yikes! I hate the grey market questions! :>) No specs to speak of, but the stock plug is D8EA for the 500s. Might even need a D7EA in colder climates. They do NOT need R (resistor) plugs because they have resistor caps on the plug wires. Check the caps for resistance around 5k ohms.
You didn't say what year it is, but with the GL prefix, I hope it is an 83 model, which had a lot of the early gremlins fixed by then.
I would suggest a peek into the air cut valve diaphragms. If it is an 83 and has the vacuum operated petcock, look there, too. When they go bad, the fuel flow drops off AND there is an intake vacuum leak through the vacuum line source (carb or manifold). Check manifolds for air leaks, too. There is an O-ring to seal the manifold to the cylinder head, that may be flattened out and leaking.

Hopefully, this is the main source of issues. CX500s had bad stators and/or CDI boxes that were intermittent and can make your crazy looking for the source of shutdowns, like this. Okay cold, then shut down when they warmed up.
When it shuts down, check for spark immediately.

That's about all I can say about this little critter, at this time...

Good luck...

Bill Silver