She won't start!

[Mitchapalooza]

Okay Gents,

Weird deal here and I'll try to keep it brief.
Before an 800 mile trip recently, I changed out the air filter, oil/filter, plugs, timing belts, final drive fluid, risers, grips, etc.  After all the changes, the bike ran great (although it developed a slight decel pop for some unknown reason).  Not the worst I've heard by any means, but annoying nonetheless.  
I took my trip with no issues and that was two weeks ago.  Since then, I haven't rode a whole lot but have pulled it out at least a few times.  I rode yesterday to work and back with no issues.  
Today, I get on and turn the petcock from off to on.  Sometimes I turn it off, sometimes I don't.  I get a few miles down the road and the bike starts losing power and sputtering like its out of fuel.  Switch it to reserve and it picks up and runs fine for the last half mile.  
I get on to go to lunch and get two miles down the road and she dies.  I pull off and check the tank - empty.  Had girl bring me a half-gallon of fuel (it had been sitting in the garage for a little while for the mower but is less than 1.5 months old) and I put that in.  Turned it to "on" and she started up fine, though a few hundred yards from the house, she started sputtering/popping again.  I'm thinking, maybe it wasn't as much fuel as I thought, so I put two gallons of fresh fuel in.
It started a couple of times after some effort, though unless I kept the throttle engaged to 1K RPM, it just dies.  Now, it won't start at all and the battery is run down.  I left it on the charger and took my cage back to work.  Not sure what could be the issue.  I checked the fuel lines and as far as I can tell without taking the tank off, all is well.  Fuel exhaust line has no kinks.  Took switch off petcock to evaluate and that looked okay.  Tried choking it (which I NEVER have to do) and nothing.  Doesn't smell rich like its flooded and there is no apparent leak with 2.5 gallons in the tank.  Tried "on" and "reserve" - same deal.  
Any ideas where I can start when I get home?  I planned for a long weekend of riding and this is screwing with my mojo.  I have never touched the carbs, though I ride pretty regularly (don't use any additives) so it's never been an issue.  With the recent popping, I can't help but think there is a bad vacuum line or something. Any advise or help in the Fort Worth (TCU) area is much appreciated!

Thanks
98' Std "Fast Black" Valk w/ 36k miles

[sandy]

First: Charge the battery and try again. The coils need 9.6 V to fire the plugs. You mentioned timing belts so I assume you have a lot of miles on her. The petcocks give trouble like you describe. Don't charge with a conventional charger unless you limit the time you charge it. Use a smart charger made for motorcycles. The popping could be due to you not getting the carb intakes properly lined up and there is an air leak on the carb intake. Do you have any discoloration around the intake runners where they meet the head? This is the O rings being bad. Let us know.

[Chrisj CMA]

A vacuum leak is a likely suspect for the popping but not the fail to start, especially since it worked ok yesterday.  Sounds a little like the diaphragm in the petcock is leaking.  If you still have the original petcock, you are a tad overdue for it to go south.  If there is gas dribbling out of the weep hole at the bottom of the fuel valve, well case close the valve is the problem.

Some of the things you describe can be related to the alternator getting weak, but with only 36K on it, that would not be expected at this time.

I would look real good at the petcock, run a couple vacuum checks on it.  1. Un hook the fuel line and see if it flows gas...It shouldn't in any position without vacuum.  2.  With it on pull some vacuum (even just sucking on it like a straw) disconnect the vacuum line to the vacuum port and attach a clean line that you can apply some suction with.  If it flows gas while on "on" and "reserve" but not on "off" with vacuum so far so good.  You also want to see that the vacuum doesnt bleed down.  If you can apply some vacuum, plug the line and it stays flowing gas and doesnt bleed down real fast, then you pretty much ruled out the petcock.  

Failure to perform as above and its probably your culprit.

[JC]

I had the same problem myself on more than one occasion.

Go back to the last work done, when you pulled the tank. I'm guessing the fuel line is not flowing downhill or has a minor bend/kink or a petcock issue. If you fill the tank completely you probably won't have an issue till you get down to a couple of gallons again. I also found that it seemed to occur more on hotter days and on long rides where the bike was pretty warm, almost as if it were a vapor lock.

Decel popping is most likely a vacuum leak, or the intake runners could have an o-ring going south or need re-torquing.

[Patrick]

When you mentioned that the 'fuel exhaust line' is not kinked, I'm assuming you mean the vent line.
So, as hard as it is to diagnose an issue on such a forum, I'm also thinking its the petcock if its an original.

[big poppa pump]

Experienced something similar about a couple of weeks back. Bike acted like it was running out of fuel and just died. Luckily I was only about a mile away from home and I somehow managed to get it back home with plenty of stops and starts. Turned out to be a bad petcock diaphragm. Luckily I always keep a couple of rebuild kits in my spare parts drawer and took me less than an hour to pull the gas tank and fix the issue.

[Mitchapalooza]

Sandy, I'll have to check the battery with a meter when I get home to see if the charge worked.  In my eyes, it should not have worn down that quickly after attempting to start for <5 minutes or so.  I know they need juice to properly start and I haven't checked the battery since I bought it.  I have it on a MC trickle charger now.  Only 36k miles, but I am the cautious type so I went ahead and did it - fairly easy job.  I know virtually nothing about the carbs on the Valk.  It is not something I've had to tackle yet, as it ran perfect for a number of months prior to the "big maintenance".  There's no discoloration around the intake runners, however there was some oil around the base of a couple (dried on there since I bought it and after I cleaned it up with steel wool, I have not noticed anything of the sort).  Not sure if this is what you mean by discoloration.  It could just need new vac hoses, o-rings or a good carb cleaning.  

Chris, I believe it is still the original petcock and it could very well be the culprit.  I noticed no gas dribbling from the weep hole, but will have to look closer.  Doubt it's alternator as well, too soon for that.  
You're saying that without the main fuel line (front of petcock) attached, it shouldn't leak gas in any position with the vac line still attached?  I'll have to play with it shortly.  If the petcock is the culprit, would you recommend rebuilding it, replacing or going with some other option?  Thanks and I'll let you know what I find.

JC, the last time I pulled the tank was a few days before that 800+ mile trip a couple of weeks ago.  That being said, I doubt that my work is the culprit since this was 1K miles ago.  However, the decel popping didn't begin until after said work.  The only thing I can think of is vac leak in one of the lines that developed after I worked on it, or the air filter (OE Replacement) didn't seat correctly somehow.  With a dozen screws and a tight fitting housing, I can't see how that's possible.  I
I did notice some oil under the air filter when replaced sitting between the intakes, but cleaned it up with a shop towel.  *Not sure what this may be indicative of, as it wasn't much and I'm not sure if that's normal  

Patrick, yes, you are correct that I meant the vent line.  Thanks for the input.

BPP, I'm hoping it's not the petcock, as I don't have any rebuild kits in sight (nor have I done one before)!  Something I can pick up at a MC shop or Stealership?

[Chrisj CMA]

Yes indeed you should be able to unhook the fuel line and vacuum line like you are going to remove the tank and even in the ON position there should be no gas flow.

If the petcock is bad, I would (I did) replace it with a manual Pingel (no diaphragms)

You will be shocked at how loose 12 of the 18 intake runner clamp screws are if you have never tightened them.  that right there is a cause of popping sounds

[9Ball]

Some of the problem might be that some crud from the bottom of the tank (when you ran it to empty) might have plugged your jets.  I'd inspect the interior of the tank when you work on the petcock to make sure it is clean.

You didn't say that you removed the airbox, but if you did perhaps one or more of the rubber intakes isn't fully seated.  You should check with an inspection mirror to see that all is OK.

Good luck with the diagnosis...

[signart]

I had the same problem myself on more than one occasion.

Go back to the last work done, when you pulled the tank. I'm guessing the fuel line is not flowing downhill or has a minor bend/kink or a petcock issue. If you fill the tank completely you probably won't have an issue till you get down to a couple of gallons again. I also found that it seemed to occur more on hotter days and on long rides where the bike was pretty warm, almost as if it were a vapor lock.

Decel popping is most likely a vacuum leak, or the intake runners could have an o-ring going south or need re-torquing.

There you go, the problem starts when you pull the tank. Go back there.

[Skinhead]

Are you able to drain fuel from the carb bowls?  If you open the drain screws and don't get fuel, check/replace vac line to petcock, or may need to install cover kit.

[NITRO]

I had two petcocks go bad on my Interstate in less than a year. Sounds just like what you're dealing with. The first time I was able to limp to my destination by filling up every 50 miles. The second time it failed on our way to dinner in north Carolina. That time she died and wouldn't fire up again.

Changing the petcock is pretty simple, you just need the rebuild kit and some patience.

[big poppa pump]

http://www.ebay.com/itm/321322333100?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

Always keep a couple of them around.

[heavyd]

If the gas can for your mower is neglected as bad for mine, I would suspect some crud to come out of the bottom of the can, could plug things up.

[Skinhead]

If the gas can for your mower is neglected as bad for mine, I would suspect some crud to come out of the bottom of the can, could plug things up.

I would think the screen in the tank has a finer mesh than the opening in the Jets and would catch any debris (I could be wrong), but you raise a good point in that the screen itself may be clogged with debris.  Again, if you can't get fuel to drain from the carb bowls, that is a pretty good indicator of where to look next.  No gas=no go.

[Valkjerk]

Although I haven't experienced this problem yet, thanks to Big poppa pump for the link. I ordered one since I have two Interstates in my stable.