Gas flow issue/Petcock Question

[glstine]

Today when I was coming back to work from lunch my 80 550 died on me when I turned onto the street where our office is and before that it was starting to cut out. Fortunately I work off of a somewhat rural street so I was able to stand on the side of the rode and fiddle with it. I looked at the fuel filter and there was no gas in it (I've got a somewhat large lawnmower filter on it) and usually it is at least 3/4 full. One of the guys I work with stopped by and helped and we got it to start and I was able to putter to the office and it died again once I got there. Started right up with the choke on and I was watching the fuel flow into the filter. At about 4k rpm's fuel was just dripping into the filter whereas normally it would flow pretty good at that high of rpm.

I just got the bike back on the rode and while working on it had to clean a bunch of rust out of the gas tank and there was also some loose debris. I have a theory that I didn't get all of the loose debris out and it is clogging the petcock screen. My second theory is when I got the new petcock the plastic strip on the side that holds the petcock screen straight was cracked. Being impatient I straightened it out and installed it anyway. So I wonder if maybe a piece of debris got through the screen and clogged the petcock.

So here is where my petcock question comes in. I have the leverless petcock. There is an arrow at the very top and a little to the left of that it says Pri. On the right and left sides are little dots. When I installed the petcock I was never able to get fuel to flow regardless of where I turned the slot, but I was thinking that prime would be when the slot is vertical and lined up with the arrow and on would be when the slot is lined up with the dots. I managed to start the bike without having to prime it and fuel seemed to be flowing fine so I didn't worry about it since I figured I would be riding enough that I wouldn't need to prime it, except every now and then. So my question is am I correct in what I think the prime position is? Also, would it be okay to put it in prime and take a can of compressed air (the type you use to clean electronics) and blow it through the fuel outlet to see if there is something in there clogging it?

Sorry for the long post.

[BassCliff]

Hi Mr. glstine,

These petcocks are vacuum operated. They will allow fuel to flow when the motor is running. The "Prime" position is to let fuel flow via gravity, without vacuum from the motor. I wouldn't leave your petcock in the PRI position for more than a minute to ensure the float bowls are filled. If you leave it in the PRI position you run the risk of getting gas in your crankcase and diluting your oil.

If you've still got crud in your tank, then your theory about a clogged petcock screen sounds quite plausible. There are some tank cleaning tips on my website, or search the forum for everything you'd ever want to know.

Thank you for your indulgence,

BassCliff

[glstine]

I've been leaving it with the slot horizontal, lined up with the two dots, which I am thinking is the run position (correct me if I'm wrong). Since I don't get fuel flow regardless of how the slot is oriented I'm just not sure. I even took apart my old petcock to try to see how it worked. Best I could tell turning the slot did absolutely nothing. I'm not real concerned about getting the fuel flow going again, pretty sure it is something simple. I am now a little concerned about why prime does not work. Also would like to know if it would be okay to blow air through the fuel outlet to clear any obstruction (if there is one).

[Larry D]

Crud, of any description, is not good living in your gas tank. Especially if there are pieces floating around loose. It would be my guess that the crud, has indeed, restricted the flow to the petcock.

Get that crud outta there !!!! I used por-15 and cleaned and lined my tank. It turned out great, just follow the direction to the "T".

In fairness, I didn't do much of the por-15 job......my lovely financee wanted to do that task.....so, I let her. She is the one who did the great job !!

[glstine]

What I can actually see of the tank looks nice and clean. I also don't see anything floating in the gas and the filter is still nice and clean.

[Rock]

Buy a Pingel and be done with it.

[glstine]

Ok I think I really kinda screwed up now. I took the petcock off and didn't see any clogs on the screen, blew are threw the fuel outlet, topped off the tank and started her up, no problem. Take some test rides up and down the street, no problem. Can see fuel flowing through the filter. Ride the 5 miles home, no problem.

After a bit I start her up and there is no fuel flowing again. I puff a bit in the vent tubes and fuel starts flowing like crazy. Great I think. Then the flow starts sputtering out. Hmm. So I puff in the right tube. Then I puff in the left tube. Air doesn't go through. So I puff a little harder, still like puffing on a solid piece of rubber, so I'm thinking great the vent is clogged, there's my problem, going to have to pull the carbs out and find out why, but at least I think I know what the problem is.

I decide to start her up one more time, and she doesn't want to start but finally does and is running poorly. Crap. Then I notice gas on the garage floor and realize its coming out of the #2 exhaust (I have a 4 into 4 slip on turnout thingy). Double crap.

Any ideas as to why the vent would appear to be clogged but push a bunch of gas into the cylinder when I puffed into it? I smelled the oil, didn't smell any gas, but I will go ahead and change it. I guess I will also pull the carbs out and check out the vent line. Very frustrating, she seemed to be running so well.