Fuel problem - I think?

Sat Nov 10, 2012 6:00 pm

I've been working on one of my Cubs and have got a problem. The Cub starts fine and runs well at idle. Throttle up and it starts to die, pull out the choke 1/2 to 3/4 and it smooths out nicely and the RPMs increase. This happens with the air intake attached or removed from the carb.

Here is the list:
Replaced points, plugs, condenser
Installed new plug wires
Timed with timing light
Removed play in the governor linkage
Fuel tank is lined and clean
Sediment bowl is clean
No fuel filter in the line
Filter screen is clear in the carb
Rebuilt the carb
Excellent fuel flow when the plug is removed from the bottom of the carb
Excellent fuel flow out the hole holding the metering jet
Metering jet cleaned with copper wire and blown out

I believe my problem is fuel related. What am I missing?

Thanks for your help.

Bill

Re: Fuel problem - I think?

Sat Nov 10, 2012 6:07 pm

Vacuum leak?

Re: Fuel problem - I think?

Sat Nov 10, 2012 6:07 pm

Bill:

Check the needle and cage.... hold the cage up to natural light. Probably a bit of varnish. Sounds like a fuel starvation issue and with all that you have done, really the cage is the only thing left....

Re: Fuel problem - I think?

Sat Nov 10, 2012 6:11 pm

Clean the carb again

Re: Fuel problem - I think?

Sat Nov 10, 2012 6:15 pm

Boss Hog wrote:Clean the carb again
My vote also. Cheap try, container of carburetor - fuel line cleaner in gas tank.

Re: Fuel problem - I think?

Sat Nov 10, 2012 6:17 pm

Get a short piece of clear tubing and the appropriate fitting to check actual fuel level in the bowl.

Re: Fuel problem - I think?

Sat Nov 10, 2012 6:18 pm

Float set properly?

Image

Re: Fuel problem - I think?

Sat Nov 10, 2012 7:06 pm

I go with clean the jet again. Every time I have had a similar problem it was the jet.

Re: Fuel problem - I think?

Sat Nov 10, 2012 7:27 pm

Wear eye protection!!

Take the jet and a can of carb cleaner with the red tube attached.
Hold jet with finger covering one of the holes in the side of it.
Insert red tube into 2nd hole, and cover withe your thumb. (same hand, LOL :{_}: :{_}: )
Spray can, observing the shape of the spray exiting the jet. It should be "conical" and symetrical.

this has the same effect as blowing it out with air, plus it will flush out any impurities, and at the same time, allowing you to SEE what the spray patern looks like.

Dale

Re: Fuel problem - I think?

Sat Nov 10, 2012 9:09 pm

How old is the fuel? Ethanol?

Re: Fuel problem - I think?

Sat Nov 10, 2012 10:53 pm

Bill, Cub 3 here, Small screw Back out on jet quarter turn or half turn should run better If so clean jet!!!!