I rode to work this morning, a 43 mile trip one way, with no problems.  However on the way back I was going about 55 and the engine starts to bog down.  I give it some throttle and it picks back up but starts to die again.  Then it completely stalls.  I coast to a stop try and start it and it just turns over and over.  I turn the petcock back to prime, wait a few seconds and try to start again.  It starts, pretty slowly idling at about 900 rpm but slowly picks back up until it is normal again.  I turn the petcock back down to normal and take off.  About 5 minutes down the road it happens again.  This time I put it on prime and leave it and travel the rest of the way home no problems with it on prime.

Does this mean my petcock has gone bade, or the vacuum line from the carb to the petcock is leaking?  Anyone have this happen to them before?  Any suggestions are appreciated.

I think it means you're out of gas.



(OK - I had to get a cat into this thread somehow. Its my job.)

Did you try reserve?

Prime takes gas from the reserve level. Tank is 4 gal (5 gal 2001+). On either, about 1 gallon is reserve.
You may think you have lots of gas, when you have a gallon left and need to be on reserve.

Your description is exactly like running out of gas. I just did that a couple days ago. With cold weather, lots of warming up and short rides (half a mile) I was getting 40 miles to a gallon and had to switch to reserve with about 100 miles on the trip meter.

I've got a 2004 so a 5 gallon tank.  I filled it the night before at the station just around the corner from me.  I went to work 43 miles and made it about 5 miles down the road before it died the first time. unless I;m getting a ridiculous 9 mpg I think I still had fuel. 

I just checked the tank and it looks like I have only used 1/4 of a tank.  I'll take it to the station tomorrow morning and top off to see exactly how much I have used.  Any other suggestions?  It was pretty cool in the morning.  Now when I say cool I mean cool for Florida.  It was in the upper 50's.  And when I left in the afternoon it was in the lower 80's.  I'm not sure if this would really affect my issue.

Thanks.

I was too impatient.  I just topped the tank off and put a total of 1.4 gallons in.  The trip say 87 miles giving me a grand total of about 60 MPG!  Great milage but it doesn't help me figure out why it stalls if it is not on prime.

Also a new symptom.  When I started it to go to the station just now it started fine on prime.  I switched it to normal and started to put on my gear.  As I was gearing up it started to putter.  I reached over and put it back on prime and it came right back to life.  I'm wondering if the vacuum hose is pinched somewhere like between the frame and airbox...

Good testing.
Yes - vacuum line pinched or it came off. Were you doing any work on your bike?
OR could be the main line from the tank to the frame petcock. There is a line for main (ON) and the line for reserve, which also is used for prime.

So check fuel lines from tank. and check vacuum line.

If reserve works, it is the line from the tank. If reserve doesn't work, it is the vacuum line.

If vacuum line is good and it is the petcock, I have extras. Just replace it. Do not give in to the "vacuum petcocks are bad" because about all bikes use them these days. They work. and like any part, one can go bad once in a while so just replace it.

Thanks Adidasguy.  I sincerely doubt the actual petcock has gone bad.  As far as I am aware its only a gate valve and a diaphragm.  As long as the diaphragm hasn't torn there really isn't anything that can go wrong with it. 

I haven't done any work on it in the past month or so, and I rode it Saturday and Sunday with no issues so it must be something clogged pinched or vibrated loose.  I will pull the tank off and do some testing on Saturday.

I'll post back when I find the culprit.

Thanks

You should be able to check all lines without taking the tank off.

OEM fuel lines can be stiff and hard. Might be a time to replace the fuel lines.

I use the surgical clamps to pinch the fuel line then take it off of the petcock. I then stuff a plug into it. That's when I'm working on it and need to take the tank off. I never remove the lines from the tank petcock.

Now what you can do is use clamps. Remove the frame petcock only because it makes it easier to check. Remove the main fuel line. With a cup or rag at hand, remove the clamp and see if fuel comes out. If none, then it is clogged or pinched. If fuel comes out, then time to check the vacuum line.

Here is my 1992 showing a clamp on a fuel line. Do this and you can pull the fuel line. Then release the clamp with the fuel line over a cup and see if fuel flows.

(See first picture. Attached pictures are not in-context but at the end of  the message)

In reality, I would have unbolted the petcock so it is easier to work on it. If I am removing the tank, I'd remove both fuel lines using the clamp then stuff a rubber cap - like you stick on the end of a line - only a small one and stick inside the fuel line. Then I can pull off the tank. I don't like removing lines from the tank petcock - too hard to do and easy to pull the brass nipples out of the petcock. Once a tank is off, then I would remove them to put new lines on. I make new fuel lines a few inches longer so there is more line to lift tank off or work on things.






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you couldnt have mentioned this a few weeks ago addy!!?? ... (thwap!) ... but yeah!! .. thanks for the hot tip now!! i will use this!! 

Here you can see how I like to make the fuel lines longer. It makes it so easy to lift up the tank or do other work without accidentally pulling off a fuel line.


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Thanks guys, when I rebuilt the engine a few months ago I added my own extra long fuel lines like adidas has.

So I removed the lines (reserve and normal) from the petcock and both let fuel run out rapidly, so I can rule out the tank petcock.  Is it a good idea to pull the petcock off, switch it to ON, remove the line that goes to the carbs, and suck on the vacuum line to simulate the engine applying a vacuum?  Or will I get a mouth full of fuel?  Is there a better way to make sure the petcock is functioning properly?

Suck away!
Put a hose on it and gently suck. It shouldn't require a lot of suction. Use a long clear hose - if fuel comes out you'll see it before you drink it.

Did you check the vacuum line all the way back to the carb? You said a 2004+ model so that would be to the right carb (89-00 it connects to the left carb). There is a wad of hoses there for emissions. Anyone of them could have come off or a "T" broke.

Keep in mind the vacuum opens the valve. If the diaphragm was torn, gas would go into the right carb and you'd be running rich and wasting fuel. If you remove the vacuum line, there should be no fuel in it. Sucking you should be able to open it and fuel flows.

Another possibility is the diaphragm is stuck closed for some reason. Sucking will open it and then it may be OK.

3rd is there is no vacuum to it. I tend towards this. The vacuum line could be pinched or came off the carb.

See the vacuum line from the right carb? It goes lots of places. To a T. Then to the vacuum operated switch. and other places. Not simple like the older carbs where it only went to the petcock.

Anyone of those lines could be off. A "T" can be cracked or broken. Or the lines to the vacuum operated switch could be broken. There is a vacuum reservoir under the tank that also connects to this line. LOTS and LOTS of places to lose the vacuum if anything goes bad.

Might be time to lift off the tank and check everything.

Yes its a 2004 so there are a wad of vacuum hoses on that right side.  It looks real ugly so when I put the carb on i tried to tuck them behind the frame, but now I can't see them without removing the tank.  Thats my next step.  If one of those "T" is broken where can I get some.  I remember looking at the ACE hardware store over by me but they didn't have any that went down that small.

Thanks,

They should be easy to find. You might have to look in the garden sprinkler area. I recall just about any hardware store having them that size - used for sprinklers, refridge water lines, stuff like that. Check all departments: plumbing, garden, automotive, etc. Car place probably has them: windshield washer line T's.

Tucking them all up may be the problem. Those things have to go where they want to go. Probably a line was tucked in a tight bend and now has bent itself closed. That could have happened suddenly.

I think we're getting close to solving your problem! 

Yes we were

I pulled the tank off and followed the vacuum line.  It got wedged between the airbox and the engine, but I didn't stop there.  I pulled it out of where it was stuck and continued tracing it up to where it enters the carb.  It was kinked twice up by the first "T".  I unkinked it and trimmed the line a bit so it fits better without being kinked.

Its storming here a bit and it's not supposed to quit until Saturday evening so I'll I won't know for sure if it is fixed until then, but I'm fairly certain we got it.

Thanks guys!

So I took the bike on another 86 mile trip to and from my office with no issues.  That confirms it was a pinched vacuum line! Thanks for all the help guys!

Congrats, glad you can ride again! Thats always the best feeling.