Topic: Engine starts and will run for @2-3 minutes then bog

[CB750 SS]

Guys, I having an odd issue with my cb750. It will start and idle easily....drive down the road then die. Wait 5 minute and it will start again....limited power.  (Dyna s w 3 ohm coils). I've had everything apart and I'm chasing my tail. It's as if I'm draing the coils and they are unable to recoup quick enough to support driving for long.  Once off, it recoups and I can start it again.  Do coils go?

[Patrick]

Is your petcock open? Is there a kink in the fuel line? Clogged vent hole in the gas cap? Sounds like it is having trouble delivering fuel. It gets there, but slowly. So it runs out of gas until it catches up. Did you have the gas tank off recently? You could have kinked the gas line. Take your gas cap off as soon as it happens and see if that cures it instantly.

Try a few things and come back.

Patrick

[Bowswell]

Gaz cap...open it and run

[CB750 SS]

Genius. I'll try that tomorrow and let you know. Thx

[scottly]

Guys, I having an odd issue with my cb750. It will start and idle easily....drive down the road then die. Wait 5 minute and it will start again....limited power.  (Dyna s w 3 ohm coils). I've had everything apart and I'm chasing my tail. It's as if I'm draing the coils and they are unable to recoup quick enough to support driving for long.  Once off, it recoups and I can start it again.  Do coils go?

There have been many accounts of Dyna s ignitions failing when warm.. 

[brewsky]

Charging system working?

It could be running on battery power till it runs down and dies.

[CB750 SS]

Charge was my initial thought too.  I replaced the stator field coil and charge is now strong.

[CB750 SS]

I tried to run it with out the gas cap on and no change.  Runs for 2-3 min.....then wont rev....then dead.  Wait 2 minutes and it runs again.   I also rerouted the gas tank vent hose. So it's probably not gas related. Coils? How does one test?

[lucky]

What year is the bike?
Has it been sitting?

[jamesb]

Have you changed the fuel lines. My friends bike was doing what yours is doing and he replaced the fuel lines and the ones he used where to soft and they would collapse and cut off the fuel. Let it set for a few and it did it again. Turned  out it was just the fuel line he used.

[Don R]

When it is dead, check the fuel line to see if it has flow. There have been problems with inline filters too. They look fine but resist flow.  Check the petcock to see if the screens are plugged. Does it have spark?

[Don R]

And believe it or not, does it have enough gas? It's happened before.

[zipper]

It sounds like the bike runs, uses up all the fuel that's in the bowls of the carbs and then dies off. That should cover 2-3 minutes of running.

Did you check the petcock? See if the flow of fuel coming out of the petcock is satisfactory, something in it could be clogged up. Are all fuel lines attached correctly? Any fuel leaks?

[zipper]

One last thing, check if all the electrical connections to the coil are attached correctly. If these aren't perfect they become troublesome when the engine starts to warm up.

[CB750 SS]

Interesting.  The bike is in the final steps of a total rebuild. So everything is clean and new.  I'll pull the pet cock tomorrow and check the filter. The inside of the tank is one of the few things I haven't cleaned.

[lucky]

Interesting.  The bike is in the final steps of a total rebuild. So everything is clean and new.  I'll pull the pet cock tomorrow and check the filter. The inside of the tank is one of the few things I haven't cleaned.

I bought a aftermarket petcock recently that would not flow any fuel at ll.

[CB750 SS]

Gents, I cleaned the peacock and replaced a couple sparks plugs.  She's running pretty well now. I just need to sort the airscrews and put some miles on her. Thx for all your help!!!!