Orvie6

My question is about hooking up the fuel system in my aircraft. I am installing a converted Ryobi 31 cc. engine in my Stevens Akro. I am using a 2 needle Walbro carb that has a 'return' line back to the tank. At least that is what I think it is... it is on the oppisite side of the carb from the fuel inlet and on the weedeater it ran back into the tank. I am using a common model fuel tank (with gasoline fittings!) and am familiar with the normal 3 line hookup to the tank...1. fuel to engine, 2. muffler pressure, and 3. vent. My question is...how is the best way to fuel this tank with the Walbro carb system? Can I just put a tee in the line on the 'return' line, like we do on the muffler pressure line on glow engines... and would the vent line cause any problems with the carb operation? I know that if there is not a line going to the tank from the 'return' exit, the tube needs to be plugged in order for the carb to draw fuel! Any help?

av8tor1977

My Feedback: (6)

The second line is for a primer bulb, which is either on the carb, or was in the line mounted somewhere on the original device. This is not a return line. You can just plug the port for this line off at the carb for aircraft use. Also, do not use muffler pressure for gasoline engines. The carb has it's own fuel pump, and muffler pressure is not needed and would be dangerous. All you need is a fuel line from the tank to the carb, and for the tank to be vented to the atmosphere. If you like, you can put a "t" in the line to the carb for refueling.

Hope this helps,
AV8TOR

Orvie6

Thanks AV8TOR,
I know you dont use muffler pressure on gas, was only refering to the line back to the tank. You have answered my question. I will seal off the 'primer' line and only use the two lines from the tank...on for fuel and the other for the vent...Thanks again.

BillS

How will you keep the vent from leaking when upside down?

Bill

Orvie6

Bill,
I never really thoutht of it, but I suppose that for no more time that I am upside down (on purpose!!!) , that what little fuel I would lose...doesn't really matter. Any thoughts?

w8ye

My Feedback: (16)

On the carbs with a return line fitting and no primer bulb on the carb, They must have a primer bulb put in the line if you are going to run the line to the tank.

Otherwise plug it. It will suck air if you don't. It'll suck air when it's end is up out of the fuel in the tank.

I've never had any trouble with my vent line.

BillS

I don’t know what should be done to prevent the vent line from leaking. Sometimes industrial equipment has a “puke valve” and sometimes a check valve. Gas caps usually have a check valve. I ran the vent line around the fuselage so that at all attitudes the fuel would need to run up hill to get away. Maybe someone else will have a better answer.

Bill

buck1856

My Feedback: (49)

on my sons D-V111,i just ran both lines out just even with the carb.one line went to carb with a tee for fueling.as your looking at the front of firewall,take the vent line run it straight up to the top of the firewall, thenturn it back down to the bottom and put a line clamp(the ones that the cable guy nails his cable to the side of your house).at the top and make a tight u shape and clamp at bottom. when the plane is upside down fuel cannot run through the u uphill.