Auxiliary Fuel Tank for Diaphragm Carburetors

[augidog]

a larger attached tank would mean some real limitations on drivetrain/chassis configs...that's my opinion, anyway.

the utility engines we're using are commonly intended for use on hand-held appliances, so the lil 17oz attached tanks are logical...maybe someday we'll generate the kind of aftermarket that would offer tanks that custom-fit XXX-engine/XXX-mount combos...

 

[augidog]

bumping for uncle_punk13 (gotta love the new shades)

 

[fetor56]

Dunno if this is exactly on-subject but i tried relocating a tank & using a diaphram carby but only had limited success....my problem was the tank needed to be 2.5' from the carby,but the carby would NOT suck fuel that far.It worked up to a distance of 18" but thereafter was hopeless.I'm assuming ALL diaphram carbies have different characteristics so wondered what the maximum successful distance anyone has ever had from their fuel tank to carby?

 

[knucklepanshovel]

Dunno if this is exactly on-subject but i tried relocating a tank & using a diaphram carby but only had limited success....my problem was the tank needed to be 2.5' from the carby,but the carby would NOT suck fuel that far.It worked up to a distance of 18" but thereafter was hopeless.I'm assuming ALL diaphram carbies have different characteristics so wondered what the maximum successful distance anyone has ever had from their fuel tank to carby?

just a thought & no experience with this but how about a vacuum fuel pump? one like they use on racing carts with the 5hp & they have the tank under the steering?

no idea if it would upset the engine & lose power? & possible slight jetting change? but should be easy to drill & tap a vacuum port & could mount a small pump & use a lower tank but would be a good project idea I think,

Later,
Randy

 

[augidog]

engine size & type, and application, dictates the carby used...i don't think it's about how far but how high you need to draw fuel. capillary-action is also a factor...if you have a solid draw but it's still not getting there, try smaller fuel line before you give up. and, ya gotta make sure of good seals at all your fittings & a suitable vent.

i dunno anything about a vacuum port being much use on such small engines...imo, a 5hp 4-stroke wouldn't have a problem on a level cart setup ...a 50cc or less utility engine, on a bike frame...i wouldn't bank on the method working.

so...somebody try it, already, and let us know

 

[knucklepanshovel]

engine size & type, and application, dictates the carby used...i don't think it's about how far but how high you need to draw fuel. capillary-action is also a factor...if you have a solid draw but it's still not getting there, try smaller fuel line before you give up. and, ya gotta make sure of good seals at all your fittings.

i dunno anything about a vacuum port being much use on such small engines...imo, a 5hp 4-stroke wouldn't have a problem on a level cart setup ...a 50cc or less utility engine, on a bike frame...i wouldn't bank on the method working.

so...somebody try it, already, and let us know

& another piece of food for thought.

vacuum could be checked while riding with a vacuum gauge to see if will maintain enough & then a T with the pump to see how it runs & it may be necessary to add a vacuum accumulator tank like we used in old days when we used camshafts with too much duration & wanted our power brakes to work, a small heavy duty can could be painted & tapped & soldered to be used to store engine vacuum, if it would develop enough. it might not work for long full throttle runs but might for city riding it will be something to experiment with..

Later,
Randy

 

[augidog]

example: tanaka PF40

somebody needed this pic.

 

[augidog]

simple single-line diagram

not very fancy but i think it's good enough to give you an idea...this setup is best used for tanks that already have 3 holes, unless you want to add one. with your main tank sealed, the vacuum created inside will draw from the extra tank, keeping the main tank full & emptying the extra tank first. this is exactly the way i did it when i had an auxiliary tank on my tanaka 40cc.


if you don't wanna drill another hole in your tank, there's a way around that...AndyT has a 2-line method that looks real tidy: http://www.motoredbikes.com/showthread.php?t=23883

 

[shawnshank]

Augidog...this is a great diagram. Perfectly simple.

In fact...if this is as easy as it looks, it's so simple, it makes all the other explanations seem overly complicated (I am only speaking for myself and my limited capacity to understand technical jargon. No offense intended).

Please tell me if I understand this correctly.

Leave the main tank the way it is with the pick up line and bottom return lines where they are (fed to and from the carb)
Replace the air vent assembly coming out of my tank with a fuel line and feed the other end to an aux tank with a vented cap?
Is that it?

I am attaching the manual for you to take a look at in case you haven't seen the air vent assembly. The air vent assembly is on page 5 and it's part #4-75.

http://www.tanaka-usa.com/pdf/dpl/utility/PF-4000dpl.pdf

SS

not very fancy but i think it's good enough to give you an idea...this setup is best used for tanks that already have 3 holes, unless you want to add one. with your main tank sealed, the vacuum created inside will draw from the extra tank, keeping the main tank full & emptying the extra tank first. this is exactly the way i did it when i had an auxiliary tank on my tanaka 40cc.
View attachment 22220

if you don't wanna drill another hole in your tank, there's a way around that...AndyT has a 2-line method that looks real tidy: http://www.motoredbikes.com/showthread.php?t=23883

 

[augidog]

it could be done as you described, but i transferred the caburetor lines down to holes 2 & 3, and used the top hole for my aux feed.

(all i did was cut the vent off of its' grommet & insert the carby return line thru it)