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Old 06-17-2011, 09:19 AM   #1 (permalink)
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Petcock problem?

I bought a '97 Fatboy a month ago, (first Harley), and it died on me in traffic this morning. The bike only wants to run when the petcock is in the "reserve" position. I was having the same problem a couple weeks ago and I took the bike back to the shop I bought it from while it was still covered by the warranty. It took them more than two weeks to replace the petcock assembly so I'm hesitant to take it back there, (I feel like that's a long time for such a little work order). Does anyone have any idea what the problem might be? Can I just run the bike with the petcock in the "reserve" position? Or would that damage anything? Any help would be appreciated.
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Old 06-17-2011, 09:39 AM   #2 (permalink)
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It sounds as if the in-tank filter is clogged. it's a screen covering the petcock fuel tube that decides the level of the fuel for normal or reserve position driving.

Not to say the petcock may have issues, but if not, simply pulling the petcock, cleaning the filter screen may solve the problem.
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Old 06-17-2011, 10:40 AM   #3 (permalink)
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Sweet, thanks for the advice. Can I run the bike in the "reserve" position without causing any harm?
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Old 06-17-2011, 10:44 AM   #4 (permalink)
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I'm think'en the shop cleaned the filter. Being it's a 14 year old bike, you might have junk in the tank clogging the filter.
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Old 06-17-2011, 10:50 AM   #5 (permalink)
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Quote:
Originally Posted by Ajiordano View Post
Sweet, thanks for the advice. Can I run the bike in the "reserve" position without causing any harm?
Yes, won't hurt a thing, as long as the other part of the petcock filter dosen't get clogged. Then you might be stranded.
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Old 06-17-2011, 10:53 AM   #6 (permalink)
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Thanks again for the help!
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Old 06-17-2011, 04:09 PM   #7 (permalink)
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@Ajiordano

If I did not understand the operation of the typical petcock, the replies to your post might confuse me further - which is another way of saying I'm old and sometimes have trouble understanding things. So . . . in case you do not know . . . refer to the attached JPEG of the petcock fuel strainer (as HD calls them) or filter, which I have cut away for illustrative purposes.

The concept of the "reserve" tank is often misunderstood. In fact, there is no reserve tank. What there is is one or two feed tubes of different lengths extending upward within the strainer from the petcock (which HD calls a fuel valve, by the way). The HD strainer uses one tube - the large central tube you see in the cutaway view. Although you cannot see it in the image, this tube ends at the wide horizontal band 2/3rds of the way up the strainer.

When the petcock valve is turned to the "On" position, fuel is fed to the engine (carb or AFI) through this tube. When the petcock valve is turned to the "Reserve" position, fuel is fed to the engine from the bottom of the strainer or a second very short tube near the bottom of the strainer. (Some applications use a second short tube to keep the fuel flowing from the very bottom of the tank where one can imagine most of the sediment would settle.)

So, I ask, why would you have to run on "reserve" all of the time? To say that the strainer might be clogged would not be the first possibility on my list because the "on" position feeds fuel from well above the sediment level. If anything, I would think that the "reserve" position would cause sediment issues.

One possibility could be that the primary feed tube (petcock in the "on" position) is blocked. Now, you might say, "They replaced the petcock assembly" - and it took them more than two weeks! Really? HD's vacuum operated petcock has two hoses (fuel and vacuum) and a nut that attaches it to the fuel tank. You are talking a two-hour job here that includes draining the tank, removing the fuel and vacuum lines, removing the petcock, flushing the tank, and reassembly. More than two weeks? They busy? Even if the shop did not have one in stock, two weeks to get one? Really? So my first question is, did they replace the petcock assembly?

Could the screen be clogged? How, they just replaced the petcock assembly? Unless one does not mind spilling fuel all over the place, to replace the petcock, one has to drain the tank. Once the tank is drained and the petcock removed, any conscientious crew would flush out the tank to remove sediment.

So, what to do? First of all it does sound like a petcock/strainer/sediment issue but how, what? Who knows? What would I do: remove the existing petcock, clean or replace the strainer, make sure the "on" position feed tube is not clogged, flush the tank, reassemble. Or, my first choice would be to replace the petcock. For $20 you can obtain a petcock that includes the on, off, reserve positions, that includes the strainer, and does away with the vacuum break (a source of difficulties). At the same time, you flush the tank.

My bottom line is, I don't know what, if anything the dealer did so I'd do it myself.

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File Type: jpg PetockStrainer.jpg (959.4 KB, 38 views)
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Old 07-12-2011, 06:13 PM   #8 (permalink)
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Hmonk, I can appreciate your logic and knowledge here on such a mundane bike part. However, in the same breath, I'll ask for additional info myself. Any source for the diafragm ? I tried Bike Bandit , but not a dealer as the closest one is around 60 miles from me. I was hoping to find one online. And for clarification my problem started after a custom tank paint, but mirrors his problem. Rich
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Old 07-13-2011, 08:51 AM   #9 (permalink)
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Plotus, after experiencing problems with petcocks (i.e., leaking, intermittent fuel flow due to a funky/torn diaphragm) one quickly learns that this dinky part can be a source of major headaches. This is especially true if one's scoot suddenly stops running as if it ran out of fuel when there is fuel in the tank. Many bikers know little about their bikes and, in this case, do not realize that something relatively simple as a vacuum leak (disconnected/torn vacuum hose) or torn diaphragm stopped fuel flow from the petcock. So while I agree that the petcock is a mundane part, it's because it is a mundane part that folks often overlook it and do not know how it works.

There are any number of kits available (Google "petcock rebuild kit"). However, if you care to PM me your "name, rank, and horsepower" I will be happy to send you one (I have lots of no longer needed parts/components that I scavenged from my bone pile). It is from the stock HD petcock; I can only assume dimensions have not change from year-to-year. Given that a rebuild kit is around $15, I opt to spend $20 on a new after-market petcock and spare myself the added work.

I attached a JPEG of the diaphragm to illustrate what I have.

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Old 07-17-2011, 10:40 AM   #10 (permalink)
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Looks like a lot of people are having this trouble. My bike acts like it's running out of gas even with gas. Putting it in reserve position clears it up for just a little while but when the tank gets to about a gallon left I have the same problem with reserve.

Things I wanted to look at 1) petcock 2) crossover fuel line and 3) in tank filter.

96 Fatboy

Wanted to drain the tanks of course but when I turn the petcock, nothing comes out. Why would harley make a vacuum petcock, what was wrong with gravity?

How do I drain the tank without making a mess. I could pull the cross over line, but that will create two flows of gas at once. Do I need a siphon?
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