Strange petcock "failure".

[BudMan]

Doing the "I just bought it" maintenance on my new Tourer and found something odd.
I took off the tank, put it on the bench and tested the OEM petcock. turned the valve to "On" and observed no gas flow; so far so good. did the same on reserve, also no flow; still all good.
I then applied vacuum to the valve and got fuel flow, still all good, then REMOVED vacuum and fuel continued to flow... all over me, the floor, things stored under the bench etc. I was so surprised when the fuel continued flowing I dropped the container I was collecting it in, had to fumble twice (with fuel covered hands) to get the petcock shut off. What a mess!
I keep a spare cover set and even a filter tube so fixing this is no big deal.
I was just wondering if anyone has seen the valve "stick" this way but it not a classic diaphragm failure?
Once the valve is shut off and turned back on, there is no fuel flow. I'll repost if I find anything out of the ordinary or damaged when I do the teardown to put in the new cover set.

Yes, I like my stock valve, no I'm not going to consider changing to a Pingle.

[BobB]

Hopefully you did not apply too much vacuum when testing the petcock and damage the diaphragm.  You should be able to suck on the vacuum line to start fuel flowing.  When using a brake bleeder, the gage should move very little...

[BudMan]

Naw, no problem there, Bob.
I just barely sucked on it just like I do every time I test one when cleaning the air filter and such. This one felt perfect...except. I MAY have felt it kind of "unstick" when I applied the vacuum. (I may just be imagining that after the fact and having it stick open.)
After this incident, I did get my MiniVac and apply about 3/4 inch of vacuum to the valve and let it set with no loss of vacuum pressure after almost five minutes.

[BobB]

Ok, it sounds like a temporary fart.  I am also one of those riders that has stuck with the OEM petcock and has not installed the DanMarc valve.  There are probably many of us, but we are a silent bunch.  In eight years, have replaced the cover set once (have another available) and I test the petcock twice a year...

[pancho]

There is a tiny hole to allow air pressure back in to close the diaphragm slowly when the vacuum is removed,, yours is probably plugged,,, a fairly common problem and easily repaired.  I will see if I kept a picture.

[pancho]

Here it is,, it is the hole at the 4:30 position.  There is also a floating ball in the middle that allows it to react quickly to a vacuum, so try not to get too aggressive with the air pressure when cleaning it so as not to damage the assembly.

[Dusty]

It's actually a rubber flap that  opens and closes on the intake  strokes  of # 6 cylinder. The little hole that you see in the picture can become plugged up with dust dirt or debris.  You can sometimes clear the debris out by spraying WD 40 or carb cleaner or compressed air in the vacuum nipple to clean it out.  I would try that and then test it a half a dozen times and if it functions properly I would leave the cover kit in the bag until you have a torn diaphragm. I imagine a lot of these cover kits get installed when all it needs is to clean that little hole .

When I have my tank off for air cleaner filter replacements I blast a bit of carb cleaner in the vacuum port of the petcock to help keep that area clean and I always check for proper operation before reinstallation.

Let us know if this works or not . Thanks

Dusty                                                                                                                                     



 

[pancho]

Sure enough, it is a flap,, nice picture.  Actually, I think you may have clued me in to this problem when I had it Dusty.  Thanks.

[BudMan]

Thanks guys!
I'll check that out today. I was going to answer last night, but was too busy starting the generator for the house, monitoring the flood waters, and trying to watch the TV for tornado locations.
Man, what a spring we're having!