mrwoody

I, just converted a Mccoullgh 32 cc engine over to a airplane motor. I have it mounted on a test stand.
The problem is the carb ( Walbro wt 312 ) is not getting fuel into the cylinder. I can get it to fire and run for 5 to 10 seconds, by taking the spark plug out and adding some fuel into the cylinder. When that burns off and the engine dies.
The carb has 2 brass tubes on it, one larger than the other. I, think the inlet side is the smaller one next to the needle adjustments and the larger one is to pressure the tank, am I right?
Any help for me out there?

Jeff

aerowoof

My experience with gas engines is limitted to quadra,us engines,zenoah,maloney,they all have a fuel pump that is part of the carb and do not pressurise the tank.the large should be fuel in,the smaller was probably hooked up to a prime blister.

Jburry

This may help?

[link=http://tech.flygsw.org/walbro_tuneup.htm]walbro carb tuneup[/link]

As mentioned above, gasoline engines do not pressurize the tank. They use the pressure/vacuum impulses from the crankcase to operate a diaphragm pump in the carburator to pump the fuel into a metering diaphragm, and from there it is drawn into the carb jets.

Good luck,

J

bluestratos

These carbs are inexpensive but good, It probably needs a new diaphram or the screen cleaned but you can buy a new one and know its fixed, lol...
Best regards,

tkg

My Feedback: (1)

The big one is the inlet. The small one is the primer pump return. Just solider it closed.

mrwoody

All I have too do is close off the smaller one? How do I prime the motor? Finger over the carb?

shaunmichaeljohnson

yep just close the smaller one.
i use a bit of silicone tube in a not but that can fall off so solder is best.
the bigger one IS the inlet.

there is no such thing as tank pressure when dealing with gas engines, the primer lust sucks fuel up the line and then any extra goes back to the tank via another line.

you can still prim it with a small squirt of fuel into the carb but this mehtod can be unreliable.
just plug the venturi with youre finger and crank it over to start it.

shaun

mrwoody

Ok, thanks for tihe info. Will try to start it again today after work. If it fires up and runs for a few seconds and dies. I will have to find out and go back to the (factory) needle settings. Do you what these are?

w8ye

My Feedback: (16)

About 2 1/2 turns on each one should be a beginning. You will have to adjust them after you get it started and see what it does?

mrwoody

Its alive. Thanks for all your help guy's!