Petcock not working in PRI

Ok, now I am confused. I have my engine running on the ON position then begins to sputter. Switched it to RES, but nothing. Put back in PRI to start bike, but no fuel flows. There is plenty of gas in the tank. As long as I keep the fuel level above the RES section (over .8 gallons roughly), fuel will flow easy on PRI. Once below that, no fuel flow on PRI. Do not understand because it should flow from the lowest part of petcock. Please help. It gets frustrating when I need to keep gas level high to ride. Thanks.

 

You ALWAYS will have a half gallon or so that you can't use, because the petcock is NOT at the bottom-most part of the tank. If it were there, you'd suck in every bit of water, dirt, etc..... that would settle there.

So if you're that low on fuel, you need to go fill up. If you think that you're still way too full, then you'll have to drain the tank, remove the petcock, and see if the screen tower is clogged .

You may also need to do a rebuild of the petcock. While you're doing that, check the vacuum hose from the manifold boot and make sure that you don't have a crack or separation, and are therefore sucking air.

dave F

 

Are you saying that you normally run the bike on prime all of the time?

If so, thats ususally a case of a failed petcock as dave already said.

However, that also means that all you are missing out on is the reserve if i understand what you are saying correctly.

The tank on your bike is not all that big, therefore you shouldnt be expecting that much range anyhow.

More importantly, If you ARE indeed always running it on prime, I would recomend turning it to the "on" position when you park it or installing an inline fuel shutoff that you would close when you park. This will prevent gas filling the crankcase in the event of the carbs failing, which can even lead to a fire and burning your garage/house down. Not fun stuff.


Good luck!

 

Are you saying that you normally run the bike on prime all of the time?

If so, thats ususally a case of a failed petcock as dave already said.

However, that also means that all you are missing out on is the reserve if i understand what you are saying correctly.

The tank on your bike is not all that big, therefore you shouldnt be expecting that much range anyhow.

More importantly, If you ARE indeed always running it on prime, I would recomend turning it to the "on" position when you park it or installing an inline fuel shutoff that you would close when you park. This will prevent gas filling the crankcase in the event of the carbs failing, which can even lead to a fire and burning your garage/house down. Not fun stuff.


Good luck!

 

I never run my bike on prime more than a few seconds just to get the carbs full. I run it on ON and when it drops to where i need to switch it over to RES, no fuel flows. When my bike is off, I check to see if I get any flow at that level with the petcock on PRI and I do not. It does not even flow fuel with about a gallon left in tank. Just not too sure what it may be. I had the petcock off about a month ago and found no problems. I did not have the money to rebuild it yet.

 

FYI, you really shouldnt have to even run it on prime normally, just after you have had the carbs drained.

Weird part on the reserve, I would check for a clogged passage on the reserve "circuit."

 

My 650 was doing the same thing!! Started sputtering when running on ON or RES, but when I would put it to PRI it ran fine. I thought it was a bad or clogged petcock, turned out to be a slit/crack in the vacuum hose going from the back of the petcock to carb boot #2.

Check it out! Might be an easy fix!!

 

I will check to see if there is a clog. There is no crack in the line. Petcock works fine when in the ON position.

 

Your petcock should NOT have any gas flow when:

1. set to ON or RES
2. the bike is NOT running.

You SHOULD have flow ANYTIME that you have the petcock set to PRI

If there is no flow on PRI, you have either:

1. a clog
2. someone opened the petcock and put it back together in correctly.

If the diaphragm is ruptured, you may/may not get flow at ON or RES, but you WILL still have flow at PRI.

Why? Because ON and RES are both vacuum activated. BUT, the PRI setting is a straight-through, non-vacuum route.

You also should not need to 'fill the carbs for a few seconds on PRI" before starting the bike. If you're doing that, then there's some other issues, as well.

Dave Fox