Stumped. Intermittent poor running issue

[fasterdammit]

As initially described in this post, my bike has begun presenting a peculiar issue when running. Basically it feels like it's either drowning or can't catch its breath. Even in neutral, when I open the throttle, the engine just isn't spinning up like normal, and it even has a bassier note to it. I thought something was amiss in the fueling - so I had the carbs cleaned, and I replaced all the fuel lines & drained the tank (in case there was some water in the fuel).

Rode it to work today and it was fine, until I was almost to work. My trip was some city roads, some backroads, a good freeway blast at ~80mph, then into the city. And the problem started right back up as I got stuck at a light for a couple cycles. It would run at idle, but as I went to give it gas, it just wouldn't rev like usual. And then when I went to get moving, I had to give it a ton of throttle and feather the shit of the clutch ... like I was towing something with it.

I checked the plugs (fine) but haven't done anything with the coils or wires. I was considering swapping to California Cycleworks' high-volt 2v coil kit anyway, but I don't know if this is the issue or not (and I'd rather throw money at the fix first, before an upgrade). Could it be that the ignition system is fine while it's cool, but once everything is warmed up and hot, it just throws the towel in?

I'm stumped. I'm not even sure where to start at this point, because I thought it was fueling-related. Your consideration and input is as always greatly appreciated.

[Tamburinifan]

Blocked tank ventilation? Try open tank when it happends again.

[fasterdammit]

Blocked tank ventilation? Try open tank when it happends again.

hm ... I'll check. That'd make sense now that you mention it; I just filled it last night, and most of my miles were at a good clip, so the fuel was moving. It wasn't until I was just shuffling along in traffic, stuck at lights, that it started giving me trouble.

Thanks. Having something to check beats standing around, scratching my head and swearing ...

[fasterdammit]

Ok, I think I'm closer to the issue. When I went leave the office, the bike wouldn't turn over - because it was hydrolocked. It tried, but it just couldn't spin the crank even have a revolution. So I put the bike in 2nd or 3rd gear and rolled it backwards about 4m. (I figured if it wouldn't go forward, maybe I could spin things in reverse and flush out the cylinders). Then it fired right up, no sweat.

So, I figure either a float is getting hung up or just simply isn't doing its job and too much gas is getting into the cylinders. The would explain why freeway blasts are fine, but idling and walking along in city traffic causes problems.

And since I'm only good at screwing a carb up, I took it to the voodoo witch doctor at my favorite shop for them to iron out. But at least I think I'm in the neighborhood of the issue ...