it usually doesn't on ours.. you can empty the tank by just temporarily putting vacuum to it. (as you discovered) On the bike the carb floats will stop the flow, and once stopped it will stay that way till vacuum is again applied.

 

ok so the petcock is good then. i guess electronics are next

 

well since you increased the jet size and it ran worse I'd think you might be running it too rich.

I have MIG exhaust on stock carbs and my bike runs fine. A bit lean, but not dangerously so and no major power issues. (runs better at altitude in the mountains where I like to be anyways, thus my taking a long time to put in the jet kit I purchased)

 

Just read through the whole thread. For what it's worth I would suggest that your issues are all in the fuelling. I spent time with mine, thinking that an intermitent stumble was electrical (it seemed to be when under load). Changed plugs that were sooty, checked leads, caps, coils earth leads.
My bike is similiar spec to yours but obviously running with Australian fuel and conditions. I had shimmed the needles after changing to Wileyco cans. Over time the misfire came back. My thoughts were that it was too rich.
Consulted one of our good local mechanics (looked for air leaks and checked my carb sync, all ok) who told me to drop the needle back down and go up one size on the mains - the reverse of what I had been thinking.
I did it even though I was sceptical. Beautiful! Fantastic result! What I had been thinking was a rich condition or electrical was in fact a lean misfire. In my desire to do the least possible work I had made the fundamental mistake of working in reverse to what FactoryPro say when jetting/tuning CV carbs - main jets first, then needle, then idle circuit.
A point to remember - from the factory Honda has jetted for leanest possible condition to minimise emissions.
Sorry for the long post, just trying to relate my experiences. Hope it helps in your thought process.

 

i'm done with screwing with it. ive got a friend with a wrecked superhawk, gonna get his carbs and put them on and see what happens. his bike ran fine before the crash.

 

Just printed all this for my mechanic. He's talented but young and we are chasing some gremlins. Performance is not one of them. 74 miles to the tank around town is crazy fast.

 

I'm thinking about a bad pulse generator, I'll check the peak voltage to make sure it put out enough, if it hits a wall in neutral and in gear at speed, it's ignition related, either loose pulse gen, clogged with steel shaving or dying unit.

 

I was thinking it could be something as simple as bad fuel. It burns fine without a load but when it really needs to burn under a load it stumbles.

Just talked to a mechanic and he says it sounds a lot like retarded ignition timing that could have been caused by simply bumping something.

 

How bout a clogged air bleed tube? Another member just experienced this and had stumbling around 6-7k rpms. Cleaned the tube and the problem was fixed!