Adding a tank to a pumper carb Honda GX31

Citi-sporter

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Jun 16, 2014
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So I've been trying to find a thread about adding another small fuel tank in series with the main tank on a garden implement Honda 4 stroke. The tank I have is off of a Ryobi and is the side mounted one from the old OHV 4 stroke Ryobi 25 cc 845R. It has two fuel line openings drilled directly into the tank. The fuel tank on the Honda is the one from the little tiller made back in the early 2000's What I'm trying to make work is having the Honda tank pull fuel from the Ryobi fuel tank. Combined they would give me a little over a half gallon's worth of capacity which should give me about 80 miles range.

Has anyone done this, as I seem to recall reading a thread here about series linking small fuel tanks.
 

carburetor al

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Jun 14, 2020
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So I've been trying to find a thread about adding another small fuel tank in series with the main tank on a garden implement Honda 4 stroke. The tank I have is off of a Ryobi and is the side mounted one from the old OHV 4 stroke Ryobi 25 cc 845R. It has two fuel line openings drilled directly into the tank. The fuel tank on the Honda is the one from the little tiller made back in the early 2000's What I'm trying to make work is having the Honda tank pull fuel from the Ryobi fuel tank. Combined they would give me a little over a half gallon's worth of capacity which should give me about 80 miles range.

Has anyone done this, as I seem to recall reading a thread here about series linking small fuel tanks.
It may be easier and a cleaner to buy a round tank that mounts behind your seat.Plus it will give you more fuel capacity.
 
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curtisfox

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Dec 29, 2008
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Is the Ryobi tank going to be higher then the Honda tank? if s you have to seal the fill cap on the lower one and let the higher tank gravity fill and breath for it...........Curt
 
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Citi-sporter

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Jun 16, 2014
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Both Al and Curt bring up good points. The Ryobi tank is going to be higher by about 2" average and yes I had planned on plugging the cap vent on the Honda tank.. Al's comment about just having a bigger tank off my seat would work if I wasn't planning to mount a seatpost type of bag carrier.

I'm trying to work with what I've got, so I don't have to purchase another tank. Filling the lower tank will be required when filling the upper one. Ryobi fuel tank is about 0.25 gallon, the Honda one is 0.17 gallon so I'm actually getting 0.42 gallons. Doesn't seem to be a big improvement in capacity but both tanks keep the engine and fuel-tanks' footprint centered and small, since this is a rack mount.
 

MEASURE TWICE

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Jul 13, 2010
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Running separate tanks with a on/reserve/off and two hose to one I thought of of sorts. In the case here which is different than a tank that has a reserve space it is just at a lower level within the tank itself I believe. While this other two tank one higher and both tanks have vented caps, you have to be sure fuel does not come out filler cap on lower tank. The valve if it malfunctions and lets gas from upper tank and lower tank at same time could have gas come out the vent cap on the lower tank which is dangerous. On my motorbike I have thought of having two tanks at the same level. I was planning on this for a while as I have a small tank and not much range. I currently use a back pack and a MSR bottle for longer range now.
 

Citi-sporter

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Jun 16, 2014
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These are the stock pumper tanks without a tap or off/reserve and the series set-up is to pull fuel from lower tank into the upper first with the upper tank providing the reserve after the lower tank empties.
 

MEASURE TWICE

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OK, I'm not too versed in all of this, but I have sees some tanks like on the two stroke engine on a Weedeater Engine. I read where it has one inlet filtered gas line used with primer bulb and the second fuel line back into the gas tank unfiltered. I guess it is so not to flood the engine in some way? There is also a diaphragm that works with the vacuum of the engine intake that makes a pump for the fuel so there is enough fuel pressure and it gets regulated. The weighted filtered fuel line inlet in the tank makes it so you can operate even upside down. The gas tank cap is not a vented one obviously in this case. I suppose some thing about the carb way it works does not need vented tank with those two fuel lines going into the tank. Eh! I had one apart an then for 14 dollars free shipping just bought another aftermarket cheapo. Will be interested in what you come up with. I have sometimes carried two bottles of fuel along to go refill the gas tank say if I know I'm going as much as 30 miles. The pack you want to have on the top bar, would like to see picture how it is used. Better having all weight off ones back. Possibly I could carry the MSR fuel bottle as extra in the top bar pack you speak of?