85 VF500F Petcock valve mod tech questions

So one day I was riding and my bike started dieing every couple of miles, and then after a few minutes starting back up again. I decided to do the petcock mod (Daugherty Motorsports - Tank Valve Petcock Modification) and it appears to work very nicely (gas comes out when it's set to the "ON" position, but not the "OFF" [duh]). I plugged the vacuum hole on the engine with a screw and the original washer, which appears to fit and seal well.
However, (here's the interesting part) when I started the bike, it had a lot of trouble running, and slowly died, and I couldn't seem to revive it. I ended up pulling off all the fuel line between the tank and the fuel pump (including the filter) and there was some gas in it.
Any ideas what I'm doing wrong? Could it die slowly because the vacuum port thing wasn't plugged properly? Air bubble in the fuel system? Bad gas? Not enough gas? Need a new filter? Stars not aligned properly for motorcycle maintenance?

 

Doing that mod increases the likelyhood that sometime a cylinder will flood with fuel when a carb float happens to stick open unless you always set to OFF when parked. Many fuel valves on VF 500s don't shut off fuel and leak constantly into fuel line.

In other words, it's better to have a working petcock than a free-flowing one.

 

I'm good about always leaving the valve off, and it's already done,

 

clean your gas cap.... i know it sound stupid . if the cap is dirty then air is not getting in and no fuel out . happen to me

 

Have you checked into Pingel Petcock valves?

 

I will try cleaning the gas cap! The tank does flow gas pretty well while it isn't attached to the bike but I'll give it a shot.

Never heard of them! Do they replace the entire petcock or just the internals?

 

Pingle makes a top notch product but unfortunately they do not offer a replacement petcock for the VF500F.

 

Alright. There's a metal valve between the petcock and the filter that I cannot remember the name for that I'm going to go clean out in a minute, and I got new fuel lines (they may have been 25 years old... rough shape). We'll see how it goes!

 

+1

That's usually the culprit. Let us know what you find out!

 

Well I put it all back together and tried to run it with the gas cap off first (more difficult than it looks because it won't give you the key back while it's off) but couldn't get it to flow any gas to the fuel filter, and then I ran out of battery. After I charge it today I'll try cleaning the cap super carefully and then give it a shot. Thanks for your help guys!

 

Hummmm..... you are running a fuel filter? Get that thing out of there and try it again.