Quick background. I have completely rebuilt this bike excluding opening the motor. The fuel pump has been removed and switched to gravity fed. All new fuel lines, new fuel filter and new petcock. Not a vacuum petcock though. Carbs also rebuilt and synced. Bike runs great most of the time.

So I took the bike on the highway to test its 70 mph speed. I got the bike up to speed but after less than 30 seconds it started struggling. I gave it more throttle but no help. I pulled in the clutch and the bike died. I pulled over and waited and it restarted without issue. I got off the highway staying below 50 mph.

Next time I ran the bike with the petcock on reserve and drove it around town doing between 35 - 45 mph. After about 40 minutes the bike started struggling again and died. I waited and again it restarted with out any issues.

I drove to a gas station and put in 4.5 gallons of gas. It never restarts immediately after stalling out. I would assume it is a fuel issue. I have already replaced spark plugs and tested coils.

So my question is this. Did I run it too low on fuel? Could my lines/petcock/filter be clogged already? Or is it likely that my gravity feed setup is an issue?

 

Why did you replace the petcock in the first place ? if it failed due to crap in the tank , is this still an issue ? Certainly sounds like fuel starvation to me . Also check your fuel cap breather , maybe an air lock stopping fuel flow . Good luck

 

That has been an issue a few times with a plugged breather tube with these bikes.

Try running it with the fuel cap open and see if it dies again. The breather may be blocked and causing a vacuum lock in the tank.

 

I replaced the petcock because the seals dried up inside. So if you rotated it to on or reserve it would leak out of everywhere. The tank was also rusty crap. I replaced the tank with a non rusty one and put in the new petcock.

Ok, so I am new to the bike world. Fuel breather cap/tube? Do you mean where you fill the bike with fuel? No way I'm riding around with that off. You have to mean something else. I did replace the fuel filler door thing with a used one because mine was all kinds of messed up.

Is there any way to test this piece without me riding the bike?

 

If your old was rusted , there is probably ****e through the whole fuel system , lines carby etc . Next time it dies , undo the cap an see if you can restart .

 

I replaced the whole system LOL. New lines/petcock/filter/tank and rebuilt carbs. I didn't run the bike with the old tank/petcock/lines/filter. If it is the breather cap how do I fix that?

 

There are 4 tiny screens under where the float valve needle rides. Did you get those?

Edit 1 per carb 4 total.

 

There is a breather tube that runs from under the tank into it. It lets air in the tank to replace as the fuel volume as the level drops. If that's plugged, the bike stalls. The harder you run the engine, the quicker it stalls. Popping the fuel cap lets air in, so if it doesn't die, you know you have a vacuum lock in the tank due to the breather being plugged. You need to run the bike with the cap open as a steep in the trouble shooting process. You may need to siphon some fuel out of the tank to drop the level to where you feel safe ridding with the cap open.

 

PMCG - I believe I replaced the screens. Can't remember it was years ago when I rebuilt the carbs.

TimBucTwo - You lost me LOL. You say there is a breather tube that runs under the tank into it. What is it? I understand the whole vacuum theory. I don't have any external lines on my tank except the one that feeds fuel out of the petcock. Is there supposed to be another line somewhere? I thought you guys were saying the filler cap was the breather vent setup.

I don't feel safe riding around without a cap on it because I am learning on this bike. Not dropping it when I ride makes me happy. I am completely green on bikes. I restored this one and am learning on this one. If I get rid of it I'm probably out of the bike world.

 

Ride it again, when it dies pull over and open the tank straight away.
You will hear a swoosh sound as air races back in(that is if your tank breather is blocked.)