I'm having a problem with a 2000 500e. It runs ok on prime but starves for fuel with the petcock on ON. I have a clear fuel  line and can see the amount of air in it grows as the bike runs for awhile. It gets to the point where I can see air being sucked into the carbs. Then idle goes down and stalls at cruising speed. When on prime the fuel line stays full. Bike info....Dynojet stage 3, washer 3rd groove, 134 main, 40 pilot, k@n lunchbox. I haven't opened up the petcock yet but what else could cause this?

nothing else

Search for "fuel starvation". The gas cap vacuum vent, carb breather line, etc, can cause those symptoms.

Do you have an inline fuel filter?

Quote from: Big Rich on September 05, 2014, 07:39:20 AM
Search for "fuel starvation". The gas cap vacuum vent, carb breather line, etc, can cause those symptoms.

Do you have an inline fuel filter?

Not fuel filter or cap vent as he said prime works. I suppose the vent line to the petcock could be suspect but he didn't say it was running bad (vacuum leak)

No inline filter. I opened up the petcock. Diapghram seems fine, no holes, except maybe a little flat around the edges. If air leaks in when on vacuum it will affect how much the diapghram opens right?

Could jetting have anything to do with it? I'm really not sure if the problem was there before rejetting as I didn't have a clear fuel line then

I'm thinking the fuel starvation problem was there only its now more noticeable as its using more gas

O-rings and diaphragm would be my bet.

o-ring only stops fuel when bike is off and a bad diaphragm (or no vacuum to petcock) stops fuel when bike is running.

Quote from: ace50 on September 05, 2014, 08:35:27 AM
o-ring only stops fuel when bike is off and a bad diaphragm (or no vacuum to petcock) stops fuel when bike is running.

You learn something new every day. So, diaphragm lol. Unless the vacuum line is clogged? No leak, but no vacuum to the petcock.

Quote from: JAS6377 on September 05, 2014, 09:06:26 AM

Quote from: ace50 on September 05, 2014, 08:35:27 AM
o-ring only stops fuel when bike is off and a bad diaphragm (or no vacuum to petcock) stops fuel when bike is running.

You learn something new every day. So, diaphragm lol. Unless the vacuum line is clogged? No leak, but no vacuum to the petcock.

I really doubt you do.
How can the vacuum line get clogged?
If it was off it would run like crap.

You really doubt I learn things?

I'm just throwing out options. I agree. If it was off and exposed to the atmosphere, yes it would run like crap. But if it was pinched or kinked, the vacuum to the carbs would still be intact.

If I'm wrong, I'm wrong. Simply say so without being snippy.

Edit: If I read into your post wrong, I apologize. It just seemed to me that you were being a little more abrasive than necessary.

Well I thought I had it licked. I saw this post about widening the restrictor plate in the petcock.      http://gstwins.com/gsboard/index.php?topic=61682.0 . So I opened it up, expecting to drill the plate. I found black sludge was blocking all the holes. Ran some carb cleaner through it till it came out clear. And a LOT of black stuff came out. Problem solved?! Nope, air is still making it to the carbs. Now I'm moving on to the tank mounted petcock to check the filter. If I understand correctly, on prime fuel is drawn from lower on the tank, hence lower on the tank mounted fuel filter. Could be up higher is clogged? Doesn't make much sense. Usually the lowest point would be clogged but we'll see. Stay tuned.

One more thing I should add. When I replaced the fuel line to the carbs with clear I definitely made it shorter. Instead of the dip it made under the stock airbox I fitted the lunchbox and ran it directly under it and to the carbs. So there's definitely an altered route from stock. Anyone see this as a problem?

Ok problem solved. It was low on fn gas! See a friend has been riding it. And after I rejetted I told him to turn the trip meter to 0 when he fills up to see what kind of mileage it gets. Which he did. And when it was having problems I got it with only 60 miles on the clock, so I figured there was at least half a tank full. When I took the tank off to check the filter (squeaky clean btw) it felt very light.
So apparently stage 3 Dynojet cuts mileage way more than I thought. Does that sound right? 60 miles to get to reserve?!

60 miles to reserve is awful.  I would still point to the frame petcock for the source of your issues.  The diaphragm seems to fail once the fuel pressure drops as the tank is emptied.

I'll have to verify he completely filled it. I do know the issue was there after I cleaned the petcock and disappeared when I filled the tank. The fuel line stayed full after pushing it to 8k. I hope someone else with dynojet stage 3 sees this and chimes in with their mileage

Most folks around here stay away from the dynojet kits.  Seems easier to get consistent smoother results with a combination of bigger genuine mikuni jets and shimming the jet needle up.  It also avoids the need to modify the slides.  That said, I can't speak from experience myself, just from watching others frustrations.

Back to the petcock issue, with your clear fuel lines, it seems like you've already confirmed that you have a problem with the petcock since you have air getting in the fuel line at the frame petcock in some scenarios.  Seems like this should never happen as long as there is fuel in the line from the tank to the frame petcock.