Dripping Fuel Problem

El Bandito

El Bandito

Member
Hey everyone El Bandito here with yet again another problem. My fuel line seems to drip fuel and it all started when I got my motor to run for the first time a couple of weeks ago. What happened was that while I was locking up the bike, I accidentally yanked on the fuel line connected to the tank and it fell off. Thankfully, I turned off the fuel line and after reconnecting it, no problems seem to arise.
Almost 1-2 weeks ago I noticed that my muffler was dripping fuel and after further investigation, it was the fuel line dripping onto the fuel filter, onto the motor head and dripping onto the muffler. So Captain Zeldacoon and I bought 2 hose clamps and put them on to the top and bottom of the tube line that connects to the fuel filter and the tank. We made sure to really tighten the top hose clamp to stop any future dripping.
3 days ago there was yet again dripping and this time as it turned out, the tube was broken partially at the top and literally got stuck in the slits of the clamp! Without even trying I removed the broken part of the tube, cleaned the tube, cleaned the valve and put the tube back on and re-tightened the hose clamp but not too tight where it would destroy the tube.
Today, I noticed, you guessed it, more dripping and this time it was dripping onto the bottom clamp and fuel filter. When the dripping occurs, it drips about the size of half a pinkie fingernail(when the fuel is on) and about the size of the top of a pushpin(when the fuel is off). The rate of dripping is about maybe 10-15 minutes per drop. I'm confused and a bit uneasy as to what's causing the dripping now. Could anyone please help me with this problem?
Broken top.jpg

Dripping.jpg

Here's how much it drips when fuel is off.jpg
 
The kit supplied fuel lines and most lawn mower fuel lines will harden and decompose with the alcohol fuels we have today. You can buy fuel line made for these fuels but it isn't cheap. Most any good auto parts stores carry it. You'll want fuel line preferably with a 3/16 inside diameter (I.D.). 1/4" will work but it is a little loose and needs to be clamped.

If you can find silicone fuel line it will hold up better than the plastic stuff but it too can suffer with the alcohol over time. Some hobby shops sell silicone fuel line for giant scale model airplanes.

If you opt to use the cheaper lawnmower fuel line you'll need to replace it periodically because of the problem mentioned above.

They make small spring style line clamps but two cheap methods are nylon zip-ties or small gage wired twisted around the line below the barbs on the nipples of the petcock, filter and carburetor.

You might also make sure the petcock where it threads into the fuel tank isn't your problem. They are supposed to have a red gasket but they can be trouble prone and leak. The fuel will run down the line and make it appear that the leak is below somewhere but in fact the petcock is leaking.
Good luck. Let us know what you find.

Tom
 
What I would do just for no future problems is go to your local hardware store and get another fuel shut off valve and some fuel line. Most places have a plastic briggs and stratton fuel shut off valve or something you could use. That is what I am using on my current build along with actual fuel line. The problem with the fuel line that comes with the kits is it becomes brittle very fast and can break easily as well as the shut off valves are very cheap. Might be worth while to just upgrade both for a few bucks and have no problems!

Edit: Ninja'd by 2door
 
Thank you for the helpful advice I'll be sure to get the new fuel line(s) and a better valve, also what is a petcock?
 
Just so you know, Bandito, the petcock (fuel shut off valve) is a machine thread, 10mm.

Most any replacement petcocks (valves) you find will be 1/8" pipe thread. Pipe thread is tapered but the 1/8" will thread into the tank but you might encounter a leak at the threads. If so there are sealants that will stop the leak. SealAll is one that is made to be compatible with gasoline, unlike most which are not. Check the label before using any sealant anywhere that is exposed to your fuel. Most silicone based sealants are not meant to be used where exposed to gasoline.

Before doing anything you might want to simply try tightening the petcock where it threads into the tank if you suspect the leak is from the threads. You might not need to replace anything but the fuel line.

Tom
 
Also plumbing tape works well on the threads of the barb which you might already have some of. Thought I'd mention that. Had to do that when I upgraded mine and it's still sealed just fine for how many threads you can actually get in
 
You can usually get a few feet of tygon fuel line. For pretty cheap off ebay or any power sports type shops locally, it stays pliable a lot longer than the kit provided line which tends to go brittle within a few days of fuel and alcohol exposure, then I don't use the worm screw type clamps because they don't stay perfectly round once you get under a certain size. The spring type pinch clamps will place even pressure all the way around the hose. Fuel injector clamps also work really well as they stay perfectly round when tightened but may be hard to find in that size, but the spring type clamps work very well. These will also prevent leaks and prevent the ends of the line from going hard and brittle since there's no way the fuel can get past the clamped end. With typical worm screw type clamps, they distort as they tighten causing the leaks, then someone goes to tighten the clamp more thinking it's too loose which makes it leak even more, also the cuts in the clamp can cut into the hose which will drastically shorten hose life or even cut thru the hose causing the leak. You can usually get an assortment of the spring pinch clamps at auto parts stores for under $10 or if you need a special size like 7mm because 5/16 is too loose and 1/4 won't go over the hose, you can get any size you need on ebay...
Another alternative, but it's not usually as good looking is to use fuel injection hose this stuff is tough, and it's typically slimmer than regular automotive fuel line hose for a given size since it's re enforced with a single layer of Kevlar vs 3 to 5 layers of cotton.
 
DZ, thanks for the explanation of the clamps! I go with the worm gear clamps mostly, but now am more informed about how they can be bad for the smaller outer diameter hose. Since I had bought new clear (probably plastic hose) that was sold in hardware store for lawn mowers I thought it would be good. I ended up getting the black rubber fuel line hose and it is thicker so the outer diameter allows for use of the worm gear clamp. The same worm gear clamp for the same barb, but using a thinner so obviously smaller outer diameter clear plastic hose would present the problem of distortion and leak as you mention.
 
I will sometimes put a bit of electrical shrink tubing on the petcock & hit it with my heat gun then put on the fuel line for a tighter fit.
 
crassius said:
I will sometimes put a bit of electrical shrink tubing on the petcock & hit it with my heat gun then put on the fuel line for a tighter fit.
Click to expand...

No offense crassius, Im certain you mean well, but I don't believe this is good advice.

A fuel leak, and a heat gun, could spell disaster. Just saying.
 
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