I've got a clear piece of tygon tubing running from my petcock to the carb header, so I can check the status of the fuel at any time. I'm not sure if this is linked to the stalling issue, but every now and then I'll get a huge air gap between the petcock and the bottom of the fuel line (before it curves back up and goes into the carbs). This isn't normal, right? The only way I can see this happening is there's an air leak at the petcock somewhere.
It's probably normal for your fuel tube routing and length, but not the way it came from Honda.
The tank to carb fuel flow is gravity fed. So, the only pressure in the fuel line, comes from the fuel volume in the tank and the height difference between the carb's float valve and the highest level of fuel in the tank. The difference in fluid height creates "Head pressure". This head pressure gets lower as the fuel level decreases in the tank.
The carbs are vented and the float valves are at the top of the float chamber. The fuel level in the carb's float bowl chamber is always lower than the float bowl valve tip and seat. When the float valve opens, air can go back into the fuel line from the carb's bowl chamber, as fuel trickles into the carb float bowl chamber.
The stock fuel line routing allows these small bubbles to rise to the fuel tap and bubble up into tank, keeping the fuel line relatively clear of large bubbles. Honda routed the lines so there was a constant "fall" of liquid along the entire length of the fuel line. This allows the fuel to accumulate at the bottom of that small tube vessel and air to rise and occupy the top of it, where the fuel tap is. Bubbles can be trapped by long lines that loop down and back up to the carbs. If the lines are long enough and the amount of air excessive, the force of the bubbles trying to rise back to the top of the fuel level surface in the tank rivals or exceeds the head pressure force attempting to let gravity feed fuel to the carbs.
The result is a stoppage or reduction of fuel flow to the carbs. When the carb bowl level drops below that of the pilot jet tube, the pilot systems starves for fuel and the mixture leans out, causing loss of power.
Complicating the matter, is the saddle hump in the fuel tank, and the stand pipe, which is used before "reserve" is selected. Fuel on the far side of the hump stays on that side, unless there is fore and aft motion of the fuel in the tank, which sloshes it over to the other side, where it can feed the fuel tap inlet. Also, the head pressure into the stand pipe becomes lower as the fuel level in the tank approaches the height of the stand pipe.
The short of it is that your long loop of fuel line may well be causing your loss of power.
This assumes you have adhered to and addressed the normal tuneup/maintenance schedule for the bike.
Cheers,
