Author Topic: petcock mystery (Read 4775 times)

rupaulpierce · « **on:** June 28, 2016, 09:57:22 AM »

Keep running out of gas with plenty in the tank. It keeps taking just over 2 gallons, so I figured the reserve flow on the petcock was blocked. Opened it up, and it looks clean as a whistle, the original screen filter even looks good... with the bowl off, fuel pours out with both "on" and "res" settings.

evanphi · « **Reply #1 on:** June 28, 2016, 09:59:21 AM »

Check that the air vent in your gas cap is not blocked.

When it happens again, try opening your gas cap to get things flowing.

rupaulpierce · « **Reply #2 on:** June 28, 2016, 10:05:03 AM »

Tried that, didn't seem to make a difference, but i'll double check.

riffman12 · « **Reply #3 on:** June 28, 2016, 10:14:45 AM »

Quote from: rupaulpierce on June 28, 2016, 09:57:22 AM

with the bowl off, fuel pours out with both "on" and "res" settings.

are you talking about with the carb float bowl off?

Have you verified that fuel is flowing through the petcock with it disconnected from the carbs?

rupaulpierce · « **Reply #4 on:** June 28, 2016, 10:24:58 AM »

Quote from: riffman12 on June 28, 2016, 10:14:45 AM

Quote from: rupaulpierce on June 28, 2016, 09:57:22 AM
with the bowl off, fuel pours out with both "on" and "res" settings.

are you talking about with the carb float bowl off?

Have you verified that fuel is flowing through the petcock with it disconnected from the carbs?

No, I pulled the petcock bowl off to check the screen filter.

riffman12 · « **Reply #5 on:** June 28, 2016, 11:42:37 AM »

OK I think your petcock is a different design than mine.

With the petcock assembled, but the fuel line disconnected - does fuel flow smoothly out of the petcock?

rupaulpierce · « **Reply #6 on:** June 28, 2016, 01:00:44 PM »

Haven't checked, but not sure I understand why it matters. The bike runs fine with a full tank of gas.

rupaulpierce · « **Reply #7 on:** June 28, 2016, 01:02:55 PM »

Now that you mention the design, my petcock has two outputs... the only logical conclusion is that the res output is clogged, i'll ride it home on reserve and see if it runs out of fuel.

flybox1 · « **Reply #8 on:** June 28, 2016, 01:15:48 PM »

The dual outlet petcock on my 550 was quite corroded internally. It is easy to remove, clean and replace. Buildup needs to be cleaned out of the tunnels to the outputs.
Both should flow gas at the same time in main and reserve. They are both ON or both OFF as opposed to main/reserve.
One output feeds bowls 1&2, the other feeds 3&4.

rupaulpierce · « **Reply #9 on:** June 28, 2016, 01:22:05 PM »

Gotcha, so now I have no idea what the problem is. It runs fine with the tank full, so all four carbs must be getting fuel, so both outputs must be clear...

b52bombardier1 · « **Reply #10 on:** June 28, 2016, 01:30:52 PM »

Not necessarily that both outputs are clear. Two gallons of fuel is a stronger gravity fed push through any valve restriction. Less fuel in the tank might not have the force to get through a partial restriction.

Rick

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flybox1 · « **Reply #11 on:** June 28, 2016, 01:36:56 PM »

+1 ^^^
Decreased flow as the tank drains, indicates blockage in the output.

riffman12 · « **Reply #12 on:** June 28, 2016, 01:56:00 PM »

the reason I suggested to check for flow out of the petcock was

a) the reasons above. potential blockage in one of the petcock outputs

b) if it is flowing fine out of both petcock outputs, then it could be a blockage or a kink / routing issue in the fuel lines to the carbs that only shows up when there is less gravitational force pushing the fuel through the lines.

ekpent · « **Reply #13 on:** June 28, 2016, 02:31:42 PM »

Are you running any inline gas filters ?

rupaulpierce · « **Reply #14 on:** June 28, 2016, 04:57:06 PM »

Little gold inline filter. Petcock screen and filter look clean. Sure enough, ran dry on res on the way home, it's not flowing. I also went to and from a gas station and I'm only getting 30mpg.

ekpent · « **Reply #15 on:** June 28, 2016, 06:44:33 PM »

Some people have reported problems with inline filters. Is your fuel line routed correctly ?

flybox1 · « **Reply #16 on:** June 28, 2016, 07:13:31 PM »

"Correctly" meaning...fuel flows downward

rupaulpierce · « **Reply #17 on:** June 29, 2016, 06:54:04 AM »

Yeah it runs fine "on". It runs fine on "res" until it runs out of gas, same as "off". The res channel must just be plugged.

Scott S · « **Reply #18 on:** June 29, 2016, 07:52:24 AM »

It's also possible that the petcock handle is installed wrong. If you've ever had one apart, you'll see a rubber disc with four holes. On the back side of the handle is a groove. That groove routes fuel to the ON and RES circuits. The rest of the handle backside is flat. If it's installed incorrectly, you're actually turning the fuel OFF.
If you have the early style petcock with sediment bowl, they're cheap and easy to rebuild.

rupaulpierce · « **Reply #19 on:** April 12, 2017, 08:13:12 AM »

Finally pulled the petcock off the bike... PO had put a piece of inner tube over the whole surface with the copper tube poking through to fix the old gasket. FYI a common 7/8" o-ring is close enough to work as a replacement.

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DaveBarbier · « **Reply #20 on:** April 12, 2017, 03:26:45 PM »

This o-ring should either be buna-n or viton. If it's a typical o-run not meant for file then it'll swell and not seal and over time will disintegrate. Just making sure you chose the right o-ring.

rupaulpierce · « **Reply #21 on:** April 12, 2017, 07:34:13 PM »

Nope but it will work till I get a real one.

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754 · « **Reply #22 on:** April 12, 2017, 10:46:04 PM »

How much are you putting in the tank when you fill it?
hmmm you said 2 gallons..at that point its still 1/2 full and not on reserve yet.. if its a honda 4.

Don R · « **Reply #23 on:** April 12, 2017, 11:14:14 PM »

Beware of the inline filter also. I've had them act up on two different bikes. They look clean but won't flow without some added pressure. I blew into the tank last time, once I did I could see fuel flow into the filters and the bike started right up.

rupaulpierce · « **Reply #24 on:** April 13, 2017, 06:09:44 AM »

Quote from: 754 on April 12, 2017, 10:46:04 PM

How much are you putting in the tank when you fill it?
hmmm you said 2 gallons..at that point its still 1/2 full and not on reserve yet.. if its a honda 4.

I hit reserve yesterday, drove on reserve for a bit and filled it up, took just under 3 gallons.

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Author Topic: petcock mystery (Read 4775 times)