Rear Diaphram carb with Front HT fuel tank.

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fetor56

Guest
I want to have a 2.5 litre HT fuel tank at the front of this bike & pump fuel (via a diaphram carby) to the engine at the rear(no standard tank above the engine)...is it simply a matter of connecting the fuel line or is their more involved?
carby.jpg

P1010084.JPG
 

BoltsMissing

Active Member
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Wild guessing what set-up you have.
In principle though,
you may have to consider the pump has to stop pumping fuel when the carby bowl fills, similar to carb engines on motor cars.
 
K

kerf

Guest
What engine is that Fector? Two stroke engines with Walbro diaphragm carbs have an internal fuel pump that should work in your application. They work off the crankcase pulse. Four strokes, to my knowledge, all have vented crankcases and would require some type of mechanically driven pump. I do recall a thread about a GXH50, where the poster thought there was a way to add a pump. Don't recall the outcome.
 
F

fetor56

Guest
What engine is that Fector? Two stroke engines with Walbro diaphragm carbs have an internal fuel pump that should work in your application. They work off the crankcase pulse. Four strokes, to my knowledge, all have vented crankcases and would require some type of mechanically driven pump. I do recall a thread about a GXH50, where the poster thought there was a way to add a pump. Don't recall the outcome.
The engine is a Titan 4-stroke.
I've got the diaphram carby but i'm concerned about the steel HT fuel tank at the front of the bike,cos all the tanks i've seen have been rear mounted plastic tanks with 2 hoses.The HT tank has only fuel to carby and i don't know what the second hose on the plastic tank is for???
I'm also concerned about the necessary length of any fuel line/lines(2.5 feet)....is a diaphram carby easily capeable of sucking fuel from that distance.
 
K

kerf

Guest
I wasn't aware that a 4 stroke carb would pump but since your does, it should work. I would assume that the second line is the overflow and you should be able to T in back into the feed line.
 

heathyoung

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Second line is the return from the primer, a T junction would work just fine.

Diaphragm carb works off vacuum pulses, works OK on 4 strokes, but better on 2's.
 
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fetor56

Guest
After testing this carb for 5 days i would NOT recommend it for 50cc engines.....35cc yes great.
Pros:
Fuel tank can be relocated approx 18" from carby(my recommended maximum distance).
Noticably increased fuel economy.
Cons:
Reduced engine power(about 20%) because of the 50% reduction in diameter(diaphram carb 10mm,standard carb 15mm)between the output of the carb & the intake of the engine.
Harder starting & more messing around because of the primer bulb.

Since i've never seen any feedback about this carb i was in the dark as to how it performed...IMO not very well,particularly when u concider under normal circumstances the engine starved for fuel & added to this i also wanted to occasionally tow a trailer.
Recommended for 35cc(or less) engines ONLY.
 
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