Can gasonline flow up?

moronic_kaos

moronic_kaos

New Member
Cracked my gas tank from engine vibes when over-reving, so I spent the rest of my $$$ on a higher gear which works great (36T vs. 48T). Rode it around the neighborhood a few times by funneling gas into the line, and no more over-reving. But I still don't have a tank.

Was thinking of rigging up a red plastic gallon-sized re-filling tank with a tube coming out of the cap & routed into the carburetor (strapped onto the rear rack). Only problem is this requires the gasoline to flow upward (out of the cap).

The tank will be vented a little, but sealed enough to prevent any spilling. I have all the materials to make this work. Obviously the line has to be submerged in the gas in the tank in order to have any chance of working. It's just a temporary system meant to last about a week or so till I get paid again. Sucks getting to work on a mountain bike with a broken gear shift.

But since the gas has to flow up and out of the cap, I was wondering if this would even be worth the effort. I've seen lawn equipment with gas tanks set up in a similar way which made me think this was somewhat feasable.

EDIT: WOw... spelt gasoline wrong in the title... lol.
 
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the carb is gravity fed, not suction fed nor has a "fuel pump". Just mount outlet of tank tube higher than inlet of carb and you'll be fine.
 
Gasoline, like any liquid will only flow naturally, downhill. As Alajoyn said, the outlet of the tank must be higher than the inlet of the carburetor. How much higher is not important but it must allow the gas to flow DOWN to the carb. Pressurizing the tank is an option but opens up a whole new can of worms that you don't even want to think about. My advice? Wait until you get a new tank.
Tom
 
moronic_kaos said:
But since the gas has to flow up and out of the cap, I was wondering if this would even be worth the effort. I've seen lawn equipment with gas tanks set up in a similar way which made me think this was somewhat feasable.

EDIT: WOw... spelt gasoline wrong in the title... lol.
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The reason for this is that these lawn equipment engines like a weed eater has a diaphragm fuel pump. Without either a pressurized tank, or a fuel pump of sorts...the simple answer is a NO. With all that said, yes I can make a liquid run uphill but not enclosed in a tube.
 
the question is where did you craked your tankif is the bolts you could grind them down and weld in some new ones thats what my mechanic did to one of his tank
 
city of angels said:
the question is where did you craked your tankif is the bolts you could grind them down and weld in some new ones thats what my mechanic did to one of his tank
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I tried that like 6 times (I'm not the best welder) & I can't get it to hold gas. I ended up with a weld like 2-3 inches thick & had to grind it back off and try again.... and again.... and again.... And I wasn't even trying to put the studs in, I was just going to weld it flat & attach it to a rear bike rack.

Anyway, it went in the trash after I went through the 3rd cutting wheel, and about 15 hours total over maybe 3 or 4 days.
 
Nitro r/c cars have a small hose from the muffler to the gas tank to add pressure to the tank to get the gas to flow uphill into the carb. I've been thinking of trying it on one of these bikes. I'll post when I do it.
 
Norm,
I've thought of that too. Muffler pressure is old tech, as far as RC planes go, and I've often wondered if we could make it work on the bikes. You're not talking tons of pressure here, just with a small tap from the muffler, a 1/4" line maybe, but possibly enough to make fuel flow from a tank that is a little low. Interesting. Why don't you try it and let us know if it works?
Tom
 
I know outboards will siphon gas. Maybe if you hook it up with a squeeze pump like an outboard you could get it to work?

Just make sure you close the petcock when not in use, if this does work. I lost about 5 gallons of gas on an outboard because my car siphoned the gas out of the tank and all over inside the engine bay one time. Lto of oil to clean up.
 
Dougan said:
I know outboards will siphon gas. Maybe if you hook it up with a squeeze pump like an outboard you could get it to work?

Just make sure you close the petcock when not in use, if this does work. I lost about 5 gallons of gas on an outboard because my car siphoned the gas out of the tank and all over inside the engine bay one time. Lto of oil to clean up.
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Think again, bad to send someone down a road you are not sure of. Outboards have a diaphragm fuel pump, the engine itself does not suck the gas out of the tank. The bulb is to get the fuel UPHILL to the pump, so the pump can work. These engines do NOT have any vacuum other then the draw through the intake manifold. The crankcase is pressurized.
 
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What about the natural ability to siphon out of a drinking cup off the handle bars. I could be mistaken I thought I saw one set up that way once. I bet it would prolly work have not tried it. That's a lot of tubing coming from a cup to the carb might hold a siphon.

Yet having gas in a potentially sloppy manner waiting for an accident might not be a good idea. It would be better to set up a real tank..
 
Here is a link for fuel pumps that will function off from crank case pressure. These are on most 2 stroke snowmobiles (tanks lower than carbs) & the old honda odesy's used them. still on a lot of go Karts also
Sudco-Mikuni Fuel Pumps

you just need to drill & tap a hole in your cases to access crank pressure & run a return line to the gas tank. not to dificult really. Hope that gives you an option. T
 
To make wht he is saying work, He would have to siphon the gas. I think I am hearing all this right? The tank is above carb height right? If so you put you hose into the gas tank that is installed on your rear rack. It has to be higher than carb level though, then pull the gas through the hose just like siphoning from a car or any jug, then when fuel starts to flow put the hose on the carb. Thats how I work on dirtbikes with no tanks I grab and old small gas can attach it to the handle bars and siphon it down to the carb. If your tank is too high though it will have too much pressure for the float needle to hold back the pressure.
 
jcchappy said:
To make wht he is saying work, He would have to siphon the gas. I think I am hearing all this right? The tank is above carb height right? If so you put you hose into the gas tank that is installed on your rear rack. It has to be higher than carb level though, then pull the gas through the hose just like siphoning from a car or any jug, then when fuel starts to flow put the hose on the carb. Thats how I work on dirtbikes with no tanks I grab and old small gas can attach it to the handle bars and siphon it down to the carb. If your tank is too high though it will have too much pressure for the float needle to hold back the pressure.
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In theory and application, yes that works. But we don't ride a HT bike like you ride a dirt bike. Here is the problem, yes, gas will flow once the siphon is started (if the fuel level is higher then the carb), but you will have to leave the gas on (unless you have a fuel cut off below the tank level) when parked. You will need a perfect needle and seat so the fuel can not leak through the needle and seat or all the gas will be siphoned out of the tank into the carb and on from there. Ending up on the floor or much worse in the crankcase. That is why a fuel cut off is supplied, installed on the tank of a gravity system. Even riding lawn mowers with a gravity system will have a fuel cut off. I've had a stuck float on my riding lawn mower and within a half an hour (did not use cut off) my tank was empty, and gas all over the deck and ground. I had to do a oil change and clean out the carb. I have never see a gravity system without some sort of fuel cut off for that reason. Had the same thing happen to a 4 cycle 5500w generator. When I removed the oil fill cap, oil diluted with gas gushed out like a sprinkler. Bad thing it was mounted and bolted on a rack behind my 37' 5th wheel. I did not know this other then smelling gas fumes one day. It is a electric start and I'm glad I checked the oil, before starting it.
 
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