The fuel pump draws fuel from the tank, where with gravity it has to have fuel in the line to work.
In other words the petcock has to allow fuel to drain into the line.
The taller tube on the petcock impedes the gas from entering the line when the tank is low.
By cutting 1/2 in. off the tube you are removing that restriction..

dennyo2 wrote:
Flashback wrote

Follow the vent hose from the front of the tank back thru the bike, around the area of the swingarm pivot you will see a gizmo that looks a bit like a pcv valve you simply pull it off and replace with a piece of tubing that fits the hose..

Why is this necessary? The float valve will only let so much fuel drain into the bowl. It should have plenty of time to equalize IMOP. Is there something I'm missing?
Denny

It's not always necessary, but they do get restricted causing a vaccum in the tank...a pump can overcome a bit of a vaccum but gravity can't....

tanman968 wrote:
Ive read so many different ways to go pumpless. Some guys swear by things that other people say aren't necessary.

I have a 99 with a stock carb.

I just ordered a Grizzly float valve.

So I guess I want to know if someone has gotten away with just changing the float valve and leaving everything else the same as pre-pumpless?

I have and mine's also a '99. There has been no change to the venting on my bike. I still have the updated rollover valve installed. My float level is set to 5mm above the rear bowl seam with the carburetor on the bike.

If it hasn't already been mentioned I would recommend removing the small filter that's in the carb fuel inlet.

Scott B.

I had trouble with mine running dry untill I routed the fuel line just right. I put a short 90 degree hose from the petcock to a small filter, then went over the intake manifold and tight down the back of it to the carb inlet, cutting the hose as short as possible without kinking it.
Before doing this the carb would starve out at about 80 mph in fourth gear if held there for a bit. Since rerouting I havn't had any trouble.

I've got a 2006 Silverado, and using the Grizzly needle & seat, all
I did was remove the little sock filter out of the fuel inlet, where the fuel hose hooks to the carb. and run the line under the intake manifold on to the petcock. I didn't have to change my float setting or remove the rollover valve on the vent hose. I've had it on the interstate 75 mph for a 90 mile run and back without any problems.
Denny

Thom M wrote:
The fuel pump draws fuel from the tank, where with gravity it has to have fuel in the line to work.
In other words the petcock has to allow fuel to drain into the line.
The taller tube on the petcock impedes the gas from entering the line when the tank is low.
By cutting 1/2 in. off the tube you are removing that restriction..

I've read about doing this but I still don't understand how it will help. When I first installed the Grizzly valve I tested it with less than 1/8 tank and the petcock set in the regular position. While riding I realized I was getting low on fuel and the last 5+ miles to the house at highway speeds was with the fuel light on and the guage reading empty. It ran fine.

The standing tube in the tank is of a larger diameter than the carburetor fuel inlet and the gravity pressure in the tube will be the same as it is if the petcock were set in the reserve position.

If the normal petcock position is causing fuel starvation before it normally would I would suspect that the screen is clogging up around the sides. A long hose hooked to the petcock and held above the tank with some carb cleaner in it and a small amount of air pressure to blow it through, with the gas cap removed of course, should clean the screen. If not and a good fuel filter is already in place then I would just remove the screen.

Scott B.

Flashback wrote:
take the petcock out of the tank and cut a half inch off the tall pickup tube....

What was your experience with removing the petcock. Easy to remove and reseal? Any tips?

deadlion wrote:
Flashback wrote:
take the petcock out of the tank and cut a half inch off the tall pickup tube....

What was your experience with removing the petcock. Easy to remove and reseal? Any tips?

I never did it as I never paid any attention to the idiot light to begin with, I just posted it cause someone asked what could be done to get the light closer in sync...my own bike will run thru a little over 3.5 gallons and then it will sputter a bit and ask me to switch to reserve...I have at this point about 1.5 gallons left, I start looking for a station.......... I have gone a bit over 50 miles on reserve, but it gets kinda iffy by then.........

I installed the Pingle, it went easy even though Makcap made me nervous since his did not go as easy. I whipped out a rat tail file, and set a high power magnet next tot he hole with the tank upright on a portable work bench I laid under it and fired up the Drill with the rat tail file and 30 seconds later the hole was big enough.

The gasket should be trimmed PRIOR to installation as it is way too big. I did use the sealer supplied and it worked great, Went just as the instructions say. My tip being the rat tail file in the drill.

The gas is MUCh easier to turn on and off, I have gobs of flow, and when the light comes on I have about 3/4 a gallon left in the tank, and it WILL run it dry! I mean dry dry.

I used a rat tail file and held it backwards with a shop vac nozzle held next to the hole. Particles come out instead of in and the vac sucks them away. Like em so well I got one for both bikes.