I *think* I read this somewhere but want to make sure. While riding today nd after a while of doing do, it started to sit and sputter. So i went from On to Pri and it came back to life.

Thinking I was just low on fuel, I filled it up, put in back on On and got maybe a mile down the road and again, it spit and sputtered. I had to put it back on Pri to make it home.

So what's the deal here? Blocked tank vent?

PRI or ON, gas still comes out of the tank and gas goes in. So not a tank vent.
If unsure, ride with gas cap not locked down.

Most likely vacuum line to the frame petcock from the carb. Check that out. Could be pinched or your frame petcock might be going bad.

If older carbs, east to trace. Just one line from the left carb. If newer carbs, there's lots of farkled up hoses for the vacuum and it originates on the right carb then goes through a bunch of T's and goes lots of places before getting to the frame petcock.

Quote from: adidasguy on October 05, 2012, 10:32:12 PM
PRI or ON, gas still comes out of the tank and gas goes in. So not a tank vent.
If unsure, ride with gas cap not locked down.

Most likely vacuum line to the frame petcock from the carb. Check that out. Could be pinched or your frame petcock might be going bad.

If older carbs, east to trace. Just one line from the left carb. If newer carbs, there's lots of farkled up hoses for the vacuum and it originates on the right carb then goes through a bunch of T's and goes lots of places before getting to the frame petcock.

Follow up.....

put the bike in the chock and let it run with the switch in the ON position and the tank cap open and it eventually would seem to run low on fuel. It would idle fine but when I would throttle it, it would bog down. Switching over to PRI and it would not do this. So I swapped out the petcock and the fuel line while I had it all apart and all seems fine now.

Any idea on what went wrong with the petcock?

Sounds like the petcock diaphragm was damaged. No vacuum means no fuel in the 'ON' position.

Hmm.....Ill take it apart and check it out

Ok, so I took it apart (carefully) and took pics of everything. The only thing I could see was a tiny orifice in the plastic between the gaskets that was blocked. If i put it to the light I could not see through it. After blowing air through it I could see clearly through it. Everything else looked good but here are some pics for anyone else interested

http://sdrv.ms/RgZI1r

Sounds like that blocked passage was likely the issue.
My bike did that when I first got it. Rode the first few months on prime, the rebuilt the petcock.

Yeah. I was leaving it on prime and most time it would be fine. But every so often the damn carb bowls would flood and leak fuel out the back of the carbs

Even if left on prime, if the floats are set properly the bowls should not flood. Are you sure the petcock was the only issue?

Quote from: GI_JO_NATHAN on October 10, 2012, 07:49:55 PM
Sounds like that blocked passage was likely the issue.
My bike did that when I first got it. Rode the first few months on prime, the rebuilt the petcock.

mos of my gs were like this. if bike was a keeper, id replace the defective petcock with a pingle.  if not she usually stayed on prime or i sourced a good one second hand, or got a decent deal on an OEM

Quote from: RossLH on October 10, 2012, 08:34:20 PM
Even if left on prime, if the floats are set properly the bowls should not flood. Are you sure the petcock was the only issue?

I wont rule out the floats but right now Im not tearing everything back apart for the one millionth time to check them. Since the mofo runs, let it run.

Quote from: weedahoe on October 10, 2012, 09:31:51 PMI wont rule out the floats but right now Im not tearing everything back apart for the one millionth time to check them. Since the mofo runs, let it run.

No need to, just use the good old clear tube method.

True. Thanks for the reminder.