Topic: 750 stalling - what am i missing.

[Shtonecb500]

I trailered a bike to my buddy in Georgia drove through like 18 hours of rain and it was exposed, when I got there the bike was stalling and dying after running for a few minutes. The petcock seemed to have really #$%*ty flow so it was replaced, replaced the gas tank lid entirely for better flow as well....I took an air compressor and blew into the old tank lid and tapped it with a screwdriver, and flow would get better...thats what made me replace the lid. Everything about it screamed fuel related.

My buddy just sent me a message and said its still doing it....it fires up, runs strong, then stalls out and needs a full choke to fire again and limp home.

Idk what to tell him at this point.

I wanna tell him to sell the damn thing...its #$%*ing nuts to me i had it running good and 18 hours of wet weather seemed to #$%* me royally.

Anyone near Valdosta, Georgia who does service calls?

[ekpent]

Is it a 1976 or older CB750 with round top carbs for starters. I remember reading about your trip.  Still has points or electronic ignition ?

[HondaMan]

If opening the gas cap lets it run again, the air vent in the cap has probably corroded itself shut (or nearly so). This is fairly common today on the 50-year-old gas caps.

[Shtonecb500]

Is it a 1976 or older CB750 with round top carbs for starters. I remember reading about your trip.  Still has points or electronic ignition ?

it is a 75/76 with round top carbs, i replaced all electrical components and has electronic ignition.

[ekpent]

 Sounds like the gas cap is not an issue if you replaced it with a good one and have tried running it with it cracked open to make sure. One thing to check if fuel related is that all the vents are clear. The four float bowl vents and the two where the rubber hoses run off the carbs by the 2 and 3 carb.
  Be nice to know if its still running on all 4 cylinders when its pucking out. Simple as touching the header pipes with a wet rag for a 'sizzle test'. Might help to isolate the problem somewhat.

[Shtonecb500]

Sounds like the gas cap is not an issue if you replaced it with a good one and have tried running it with it cracked open to make sure. One thing to check if fuel related is that all the vents are clear. The four float bowl vents and the two where the rubber hoses run of the carbs by the 2 and 3 carb.
  Be nice to know if its still running on all 4 cylinders when its pucking out. Simple as touching the header pipes with a wet rag for a 'sizzle test'. Might help to isolate the problem somewhat.

i remember it firing only on 2 when i was there, im sure its doing the same thing. Next time he has time to take it out ill have him try and test the headers.

[newday777]

Sounds like the gas cap is not an issue if you replaced it with a good one and have tried running it with it cracked open to make sure. One thing to check if fuel related is that all the vents are clear. The four float bowl vents and the two where the rubber hoses run of the carbs by the 2 and 3 carb.
  Be nice to know if its still running on all 4 cylinders when its pucking out. Simple as touching the header pipes with a wet rag for a 'sizzle test'. Might help to isolate the problem somewhat.

i remember it firing only on 2 when i was there, im sure its doing the same thing. Next time he has time to take it out ill have him try and test the headers.

Bad plugs and bad plug caps can cause that from being wet, as well as bad plug wires or a cracked coil.

[ekpent]

Sounds like the gas cap is not an issue if you replaced it with a good one and have tried running it with it cracked open to make sure. One thing to check if fuel related is that all the vents are clear. The four float bowl vents and the two where the rubber hoses run of the carbs by the 2 and 3 carb.
  Be nice to know if its still running on all 4 cylinders when its pucking out. Simple as touching the header pipes with a wet rag for a 'sizzle test'. Might help to isolate the problem somewhat.

i remember it firing only on 2 when i was there, im sure its doing the same thing. Next time he has time to take it out ill have him try and test the headers.

If 1 and 4 and or 2 and 3 as pairs are not firing then its time to look at ignition problems possibly.

[Airborne 82nd]

Pull the plugs out put them back on the coil wires. Then ground the plug to the engine. Do the same thing with the 1 or 4 plug and compare spark. Best if done in the dark. If they are the same then forget about spark and move to gas. If they are NOT the same I would be trying to dry everything out.
Wash down the 2-3 coil and coil wires along with the control wires and ground with contact cleaner remove the plug caps and spray them down good. Nip a 1/4 inch off each wire. Then spray down your electronic ignition. Make sure the cleaner says safe for plastic on the can.
"My buddy just sent me a message and said its still doing it....it fires up, runs strong, then stalls out and needs a full choke to fire again and limp home." How long does it run on all four before it does this? Does the 2-3 cut out real fast or does it sputter for a little bit  This could be heat related. How long does it have to sit before it fires back up on al four? The main thing stay on one thing fire until you know it is good then move to fuel or air. do you have pods or stock?