1985 VMax Starving of Fuel

[schenckster]

Alright, I am about to lose my damn mind. My Vmax has been having this issue intermittently for the last year or so. I will be cruising then the bike starts to starve for fuel. I have noticed it only does it when the bike is warmed up, typically on the ride home from wherever I am going. Seems to happen randomly. Once it happens, I pull over wait 5 minutes start the bike back up go another mile, rinse repeat. Then next day, its like nothing ever happened and the bike rides great.

I have replaced the battery (voltage looks good), the fuel pump, the fuel lines, fuel filter, opening tank cap to breathe doesn't help, and preformed the shotgun multiple times.

When the issue occurs no fuel is being pulled from the tank, it just sits and clicks. You can visibly see a tiny bit of air coming from the fuel tank line into the filter, even when fuel tank is topped off completely. I had a thought that the fuel inlet could be clogged , but that doesn't explain why the next days it starts working again. Any thoughts?

 

[Fire-medic]

I'd check fuel lines/fittings for cracks/leaks. Something you haven't thought of yet is allowing in air. Try back-filling the gas line on the top of the tank with compressed air and see if you can see/hear any leaks.

 

[Ddalton71]

I had this happen on a different bike, 86 Radian, problem was debris inside the tank clogging the petcock screen. Leaning over on the kickstand the debris would slide away and when stood upright riding position it would begin to gather around it and starve the engine. Had to clean out the tank. I know it was a different setup but could still be doing the same kind of thing on the vmax. Just a suggestion hopefully you find the issue.

 

[MaxMidnight]

I would check that the breather is clear - when it is playing up, stop and undo the filler cap and listen for air being drawn into the tank. If not done within living memory also change the fuel filter.

 

[Fire-medic]

OK, what guitarist is gonna tell us what note is the string to clean the breather port?

 

[schenckster]

Well I removed the fuel tank and found the problem. The fuel tank main inlet is clogged/closed off. There was very little rust in the tank, only 1 spot with a 3 or 4 small dots of rust. I used compressed air to try and clear it but it didn't do anything. Got a guitar string and ran it into the main inlet and saw a small amount of debris lining the guitar string but not significant.

I also used compressed air through the fuel tank overflow inlet and found it takes about 15 seconds for the main inlet to let the pressure out. So it must be pretty bad.
It looks as through the bottom of the main inlet is sealed the the bottom of the tank, is that normal? It could be possible that the tank was resealed and it closed around the inlet but I'm not familiar with the sealing process and not sure if that's possible.