The stock vent setup has a restrictor in it and also "rollover" valves which are a form of check valve. This works OK with the pump because it will pull the gas out of the tank.

Any restriction on a gravity system will cause problems and if there is even a slight vacuume in the tank the gas will not flow

The tank vent is very small. They do have a tech article about drilling it. The pingel is a much nicer and higher flow than the stock.

The stock vent system and petcock will freely flow more than twice as much fuel than the engine can possibly use. I've tested it.

I had a similar problem when I went pump-less a bout 2 yrs ago I would be on the HWY and it would start starving for gas at, But it wouldn't do it all the time. So this last winter when I had the bike apart for paint I cut the pick up tube down and re attached the screen, haven't had a prob sense. a I also went with the Kuryakyn 8309 vented gas cap.

texasscott1 wrote:
The stock vent system and petcock will freely flow more than twice as much fuel than the engine can possibly use. I've tested it.

Just to make sure I understand(I'm pretty sure i do ). You are confident..ie..IYHO... that I could put one or both of the plugs back into the cap if I wanted, and probably suffer no side effects(I saved them)....I still have my roll over valve installed on the regular vent line.
I'm in complete agreement regarding the flow capacity of the stock petcock. I only had to forget to turn the fuel off just one time, before removing the fuel line at the carb, to notice that
I can see the value of the Pingle for the single pinkie operation...plus the added conversation potential when the weather becomes a slow topic

SKWEARpeg wrote:
texasscott1 wrote:
The stock vent system and petcock will freely flow more than twice as much fuel than the engine can possibly use. I've tested it.

Just to make sure I understand(I'm pretty sure i do ). You are confident..ie..IYHO... that I could put one or both of the plugs back into the cap if I wanted, and probably suffer no side effects(I saved them)....I still have my roll over valve installed on the regular vent line.
I'm in complete agreement regarding the flow capacity of the stock petcock. I only had to forget to turn the fuel off just one time, before removing the fuel line at the carb, to notice that
I can see the value of the Pingle for the single pinkie operation...plus the added conversation potential when the weather becomes a slow topic
After thinking about all this I would have to agree provided all is in good working order or removed like the roll over and the one I've been reading about located on the inside of tank supposedly on the vent tube.

"Iron sharpens iron" That's what I love about RSC

On mine with 3/4 tank the stock petcock with the stock vent system will flow about 26 ounces/minute from the petcock. That's with a hose held level with the petcock and gas draining freely. It will drain a little faster with the cap off but as you can see from what the needle and seat allows to flow that's more than enough.

When I had the pump installed and the float level set correctly the most that would flow from the needle and seat with the bowl off and the float at full drop was 12-13 ounces/minute which doesn't seem like much until you realize it amounts to about 6 gallons/hour. Without the pump I set the float level to duplicate that flow and found I still had to set the level a little higher.

The lower running level experienced with gravity feed is the reason for the starvation issues at high speed. The level in the bowl seeks a certain level according to demand (speed). It's more difficult to find the same running level that is experienced with the pump when running pumpless.

I've had to drain a full tank before into a 5 gallon container and it doesn't take long. I always leave the cap on so nothing can fly in there.

texasscott1 wrote:
On mine with 3/4 tank the stock petcock with the stock vent system will flow about 26 ounces/minute from the petcock. That's with a hose held level with the petcock and gas draining freely. It will drain a little faster with the cap off but as you can see from what the needle and seat allows to flow that's more than enough.

When I had the pump installed and the float level set correctly the most that would flow from the needle and seat with the bowl off and the float at full drop was 12-13 ounces/minute which doesn't seem like much until you realize it amounts to about 6 gallons/hour. Without the pump I set the float level to duplicate that flow and found I still had to set the level a little higher.

The lower running level experienced with gravity feed is the reason for the starvation issues at high speed. The level in the bowl seeks a certain level according to demand (speed). It's more difficult to find the same running level that is experienced with the pump when running pumpless.

I've had to drain a full tank before into a 5 gallon container and it doesn't take long. I always leave the cap on so nothing can fly in there.

You may have mentioned and I forgot, but was this testing with the stock 2.0 needle and seat? The increased volume from the 2.5 and 3.0 should compensate for some of the flow loss from going pumpless with the 2.0.

The testing with the pump installed was with the stock 2.0 seat. Pumpless I was running the 3.0 grizzly valve.

Even with the Grizzly valve under gravity the float running level will be much lower than with the pump installed. The pump can supply a lot more fuel when the float valve first starts to open than the Grizzly valve can with gravity feed.

If you're a tinkerer and want to test this then before removing the pump hook up your float level tube and start the engine. With the choke all the way in make a note of the fuel level and then pull the choke all the way out. Mine drops 1-2 mm's with the choke out and stays there. I can also feel the pump speed up slightly to keep up with the demand.

After the Grizzly valve is installed and the level is correct check the level change between normal idle and with the choke pulled out. The level will drop a LOT more before the valve is open enough for gravity to keep up with demand.

Even after I raised the float level quite a bit with the Grizzly valve mine would still suck the bowl dry at 95, 4th gear full throttle. I thought about leaning the main out but the plugs are just right and it pulls hard.