The Happy Time Motorized Bicycle Teardrop Tank Is Not Flowing.

I have dual 43cc Mitsubishi 2.2hp engines on my bike "Mr. Hyde", each with their own 30-ounce tank. It was very difficult to fill more than half their tanks on flat ground. I had to literally run the bike up a tree in order to add gas after less than 20 miles each day. It was impossible to fill to maximum because the bike had to be standing on its back tire and perpendicular to the ground.

Sooo, I installed a Happy Time teardrop tank on the top bar to feed both engines. The three tanks' fuel filters were removed and a FRAM inline filter installed after the petcock. Below the filter lies a t-fitting which fed 1/4" hoses and 3/16" steel lines towards the engines' tanks. Brass barb fittings were installed atop the engines' plastic tanks to link to the auxiliary teardrop tank.

When I filled the teardrop tank for the first time, the fuel did not flow down into the FRAM filter. I had to fill the engines' tanks directly thru their caps. Fuel finally filled the filter the next day, but has never flowed into the tanks.

The teardrop tank and FRAM filter is above the engines' tanks, but the lines might be below the engines' tanks' level. It's strange that absolutely no fuel siphoned downward while I'm riding "Mr. Hyde".

I'm carrying a 4 foot hose to siphon-feed both tanks from the teardrop tank until I solve this fuel delivery problem

Can anyone figure this out?

copied/pasted from xPosTech in the other thread

Sounds like the lines have an air block(s) at the lowest point before the engines or an air leak in the lines. The petcock on the teardrop may be plugged. Solving the air leak problem is obvious.

For the air block, first make sure the teardrop cap is vented. A siphon won't flow unless it gets air above the level of fuel. Make sure the petcock is turned on. Test by disconnecting at the T and checking flow. Reconnect the line.

Remove the air block by removing the gas caps on the engines and slightly pressurizing the teardrop tank with it at least half full. This should force fuel through the lines to the engines, clearing the air block(s).

Be aware that the siphon probably won't stop when the engines' tanks are full. You will have to manually turn the petcock on/off.

After thinking about your setup for a while I have another idea. If you plug the vents on your engines' tanks' caps and seal the input lines at the top of the tanks coming from the teardrop, the engines should draw (from the very slight negative pressure from those itty bitty fuel pump diaphragms) directly from the teardrop to the engine tanks. When the engines aren't running, they won't draw. However any air leak in the lines would prevent this and also cause a fuel leak after they are shut down, even though you turn off the petcock.

This is interesting. Please keep us advised of the outcome.

Good luck.

Ted

PS - If you do set it up for drawing directly be advised that you will not be able to remove the engines' tanks' caps with fuel in all the lines. The tanks will overflow slightly. That may be of no concern to you, but I hate fuel spills however slight. Valves at the top of the tanks would allow you to do so.

You could also connect the teardrop lines directly to the carbs once the no siphon problem is solved.
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copied from comfortableshoes in another thread

here's a thought, you said you are using a FRAM filter? Is it one for small engines or for a larger engine with a fuel pump, some of those larger filters need the pull of a pump however small. Gravity in that case just wouldn't be enough.
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Re: The Happy Time Teardrop Tank Is Not Flowing.

Thank you both for responding with excellent suggestions. I will check on them all.

Ted might be right about air blockage in the lines. When I filled the tank for the first time, literally not a drop of gas flowed into the filter for hours. If it needed a suck from the engines like comfortableshoes suggested, the gas would have at least drip into the filter's neck and sat atop the paper element.

I don't think there are any air leaks and definitely no fuel leaks. All fuel connections were so tight I had to use thread sealant as a lube to push on the fuel hoses. All three tanks are vented thru their caps. The teardrop tank is vented through the keyhole in the locking gas cap. I gave it the "suck/blow" test.

At least I can use the teardrop tank as a storage tank and siphon to both engines' tanks until I solve this problem.

Re: The Happy Time Teardrop Tank Is Not Flowing.

Ted, the carbs are being fed by the tanks below the engines. There is no fuel flow from the centralized teardrop tank to either engine tank. I don't think both lines would coincidently be plugged by sealant after the tee fitting.

The fuel filter is now filled with gas.

I think it is air in the fuel lines ANNND insufficient fuel SUCTION from the carbs, especially since there are no fuel pumps. I think another part of the problem is the fact that the rear engine's tank is higher than the lowest part of the new fuel line. That is why there is no siphoning effect to the rear engine.

What has led me to that conclusion is that before I revamped the fuel system, my new engine would stall after every two miles of running. I would have to get off the bike and loosen the fuel cap. The engine would restart after two pulls and perform perfectly for the next two miles and quit again.

Yesterday was my second day of running the revamped bike, and I've logged about 30 miles. The new engine has NOT quit on me once, which proves there is no longer a vaccum problem because of excessive air in the fuel system.

What I'll do to troubleshoot this problem is separate the fuel lines feeding the engines' tanks. Since the front engine's tank is completely below the teardrop tank and its line, fuel should then siphon downwardinto the front engine's tank. If it doesn't, I'll open the cap to remove air trapped in the tank. Then fuel MUST flow, according to the laws of physics.(unless the lines are plugged, which I doubt)

With the rear engine's tank ABOVE the feeding fuel lines, I need to RAISE the bike's front when I want to transfer fuel from teardrop tank to rear engine tank. Gravity SHOULD allow fuel to flow downward into the tank. I can't open the tank because the cap is on the tail end and will spill fuel. The air in the rear tank will have to escape thru the fuel line to the teardrop tank. If the air cannot escape, I will have to either drill and tap an air valve (hole) in the tank near the fuel inlet ORRR carry a siphon hose and use that to transfer gas from teardrop tank to rear engine tank.

Re: The Happy Time Teardrop Tank Is Not Flowing.

I just had a brain flash.

A few days ago, I siphoned fuel from the teardrop tank to both engines' tanks. Of course I had to suck on the hose to start the siphoning.

That might be why there is no siphoning effect.

I might have to gravity-feed both tanks individually by keeping the teardrop tank above the engines when it's time to fill them.

Or instal a fuel pump under the teardrop tank.

Siphon Bulb?

I believe the fuel line has air in it, which needs to be pushed thru the lines towards the fuel tanks.

What do you think about installing a siphon bulb squeezer in the line below the fuel filter? Do you think that squeezing the bulb several times might start the siphoning effect downward into the tanks?

It's worth a try. I just bought the $7 pump yesterday, because I'm having to siphon gas from teardrop tank to engines' tanks. I'll hook it up after the filter and see what happens tomorrow. That should be easy enough, and cheaper than rigging up a 12-volt electric fuel pump.

If it works, the siphon bulb becomes a permanent part of my fuel system.

Re: The Happy Time Teardrop Tank Is Not Flowing.

Well, I plumbed the siphon bulb just below the fuel filter. With a whole lot of pumping the bulb, gas filled both tanks, but not to capacity.

There was still a lot of air in the lines.

Then it hit me!

The fuel lines to both tanks end with barbed fittings mounted near the top of both tanks. Fuel and air pushes thru the lines by squeezing the siphon bulb. When I release the bulb, the bulb sucks air back into the lines from the tanks.

I need to change the barb fittings to ones that will extend the auxiliary fuel lines to the bottom of the tanks, below fluid levels. That should allow me to easily fill both tanks, and maybe allow the front tank to siphon on demand.

Stay tuned.

Re: The Happy Time Teardrop Tank Is Not Flowing.

The darn 1/4" double hose barb fittings that I need cost $30/pair!

Okayyy, I disconnected the fuel line from one tank. Hmm, a 3/16" steel line looks like it'd slip right down the 1/4" brass fitting. So I measure the tank's depth, cut 4" off a spare 3/16" fuel line. ..perfect fit. Flared the tip, air-tight connection, reconnected the fuel line.

Saved $15.

The second tank has a 90-degree brass fuel fitting on the top. I need to drop that tank, change to standard 1/4" barbed fitting, then slip the 3/16" line thru the fitting into the tank. Since the tank is down, I might as well attach a short fuel hose in the tank. If I don't, the 3/16" tube extension might be sucking air.

The fuel overflows out of the gas cap before the tanks are 2/3 filled.

Go figure.

Re: The Happy Time Teardrop Tank Is Not Flowing.

Joe, the locking gas cap is vented thru the keyhole. I used the suck/blow check.

The fuel flow problem exists even when the cap is off.

Re: The Happy Time Teardrop Tank Is Not Flowing.

Hooray for the primer bulb!

Without the bulb plumbed right below the filter, I'd be siphoning gas to both tanks. Squeezing the bulb, it takes a few minutes to fill each tank on flat ground. No need to run the bike up the tree anymore to fill gas every 10 miles.

Still a lot of air in the system. First I'll remove the brass elbow, run a straight 1/4" fitting and insert the 3/16" steel line and a 6" hose.

The extra parts are laying around somewhere, and will save me another $15.

If that doesn't work well enough, I'll drill the tanks and install vents.