sputtering carbs

[HurstRob]

 I have a problem I want to put to the resident VAlk enlightened experts. On a fairly regular basis the old gal will start sputtering and loosing power for no apparent reason. She acts as though there is  water in the fuel. I can turn it to reserve and it will clear right up and then back to regular tank and its fine. I wonder if I can be getting condensation in the tank because of the hot humid days and cool nights. I would be interested in all thoughts.
HurstRob

[BradValk48237]

Check the vent line on the tank...... if its not kinked then you are probably having petcock issues.....

I had to rebuild it twice...... fairly common

Brad

[Brian]

By going to reserve you pull from the bottom of the tank where the water would be. Have you run any techron or seafoam thru? I assume you are using the stock vacuum actuated petcock? I feel all the other mechanics here will ask these questions. I would think if this was happening all time I would suggest checking all the vacuum lines and the intake O-rings.

[Grandpa Bigbuck]

Sounds like you might have a split diaphram in the petcock. Easy and cheap fix.

[nogrey]

I have had this exact issue on both of my Valks. You have a bad petcock. I rebuilt mine twice and still had the issue. Finally replaced it altogether with a Pingle petcock. Problem solved.

[whitestroke]

Sounds to me like there is crud sloshing around in your fuel tank clogging the filter. Take it off and clean it out thoroughly. Might as well rebuild petcock if its never been done, also made sure all fuel lines from petcock slope down.

[Patrick]

Yep, what the fellas said. Whatever it is, it should be an easy fix. Pull the tank and clean it. Check and fix the petcock or replace it with a Pingle. Replace all the vacuum lines and caps if they haven't been done in awhile. Make sure to not kink the vent line when replacing the tank. Doesn't really take too long.

[98valk]

the org petcock diaphragm failed at 13k miles. put a new one in with a snubber in the vacuum line, now approaching 40k miles and still no problems.

[Ricky-D]

Seems to me a few missed the part where you say the problem clears up when you turn it to "reserve".

So all the comments about crud, sediment, or rust are misplaced.

My feeling, like some others have said, is that your petcock is bad.

Replacement would be the best course of action.

***

[whitestroke]

Ricky I've had clogged fuel filters that would make vehicle sputter, and when shutting vehicle down crud would fall off and upon restarting vehicle would run good till crud got sucked up to filter again. Since reserve sucks from a different area of the filter crud would fall off.
Regardless clean the tank and eliminate that possibility since it's coming off anyway.

[HurstRob]

Thanks for the replies. I rebuilt the petcock 5K miles ago but I bought two sets so I can do it again. I have run Seafoam in it about every other tank. One other thing; and the wife reminded me of this, it almost always happens on a full tank.

[Flrider]

Might as well be sure and take off the tank, take off the petcock as your are about to rebuild it.
You will be able to check a kink on the vent hose, check the screen that is inside of the tank for any crud and check for a dirty tank.

You will have peace of mind and you will know where the problem came from.

Keep us posted as to what the problem was.

[nogrey]

I didn't miss the part about switching to reserve. As I said in my original response, I had the EXACT SAME PROBLEM, exact being the operative word here, as in  same, identical, non-different problem. Switching to reserve always fixed it. I rebuilt the petcock, no joy. Replaced the pet cocky with a pingle, problem solved.

[longrider]

I am with tHe others on this one.  A Pet rooster problem only 5k miles after rebuild isn t right.   I've experienced the same.  When the diaphragms are being replaced we all twist the rubber nibs into the spacer.  This can result in a tear so small it can't be seen.  I now use a little silicone grease on those nibs and they require very little effort to get in.  Should then last a long time

Warren

[olddog1946]

Heading to Inzane 13 my petcock went belly up about 230 miles out from La Crosse, while I had a rebuild kit with me I didn't want to work on/around a hot motor and limped it in (20-30 miles at a time).
When I arrived I had BigBF rebuild it using the factory kit and I saved the cheapy one. I didn't ride it after the rebuild, until the end and I headed out to Illinois to see my sis. 23miles down the road, spit and sputter and died. I had purchased a new petcock from Big Mike for my next door neighbor, so I pulled the rebuilt one and installed the new one. Went to Ill. without any problem, then while there, same thing happened...this time I put the original back in which worked fine all the way back to Wa. state..
Took the new one and put it in my neighbor's bike (his originally had no reserve) and the new petcock had no reserve,,,,,,,,,,,made no sense... In checking the old one everything worked as it should while off the bike, the only thing different was the screen/o-ring. I put a new o-ring and screen on the old petcock, re-installed it in the tank and he's been using it since. I now have the new one as a spare.

My point to all this is:  Remove the screen and o-ring and mount it on the petcock, then install into the tank. This might take care of your problem.