Vapor Lock First Gen.

HI, I searched the forum but didn't find a definitive answer.

This was found in the "what gas u use thread." I am having same problem. Is there a fuel pump I can look at replacing on this rig? Water temp seems fine.

vf700f 1985.

 

Don't know about vapor lock-up being dependent on octane.

Several Things:
The first generation bikes are made to run on 87 octane. Any higher and you are just wasting money and possibly hurting your engine. In a nutshell, high octane gas contains combustion inhibitors so it will not ignite under high pressure and high temperature. The first gen bikes do not burn high octane gas thoroughly so it leaves carbon deposits on your pistons/valves.

Sounds like your fuel filter is the issue. I had the same problem after high speed runs (hwy traveling). I couldn't find the OEM filter so I put one right after the tank. Try removing the fuel filter(s) completely and see if that fixes it.

Make sure you only have one fuel filter (stock location is under the fuel pump) and if you put one in another spot, DO NOT put it between the pump and the carbs. I like to put it just after the main tank so I can look at it and replace it by just pulling the seat

Replace the fuel lines - especially the ones under the fuel pump.

In fact, I removed my fuel pump completely and now run straight from the tank to the carbs.

There is a fuel flow pump test in the manual. Basically you short the pump relay (don't short the wrong two wires or you will fry your pump) and measure how much the pump flows in one minute.

 

Thanks! I will look at this stuff.


EDIT:

It is not vapor lock. When it starts to die, I can park it for hours and it takes 3 minutes or so to get whatever the obstruction is out of the way.

down to 1/2 a tank. When near empty, I will check entire fuel system.

 

Sorry to double. It isn't vapor lock.

My rig quit running Sat night. Boo.

I took tank off, gas isn't brown (but that is the color of the shit that came out), and it was only a day old. There is rust in the tank or something. Now I need to replace fuel filter to see how far sludge got.

Also there is a small line in the front of the tank with a 90 degree bend in it, its that for vent?

 

sounds like it could be rust I would drain the tank best you can and take a look. If it is you can get most radiator shops to line the inside for you.

 

Thanks. I got a new filter for 12 bucks I will add that just cuz I I have it now.

Now I will call radiator shops