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B acts like its running out of gas

M

makin hay

Member
I changed the gaskets in the Zenith carb on my Cultivision B. Now she starts good and runs at any speed for 5-10 seconds and then acts like she is out of fuel. It will run if choked half way or so, but not well. I am convinced it is fuel related but am at a loss.

Fuel line is clear, new needle/seat, all ports cleaned good, etc... Any ideas?? Thanks!!!
 
The connection from the tank to the Sediment bowl is likely to be clogged. The best is to drain the tank (slow if necessary) into a clean fuel container, through the fuel line. Then remove the sediment bowl and clean it and rinse the tank with some of the old gas filtered through a coffe filter. Then reassemble.
Also the main jet in the carb can be partially clogged by a tiny flake of varnish. Jim
 
Thanks!!


Is 1 1/4 turns a good starting point for the mix screw? I have done what you said, and am re-installing almost ready to give her a whirl.
 
Sure, the amount is not critical but between that and 3 turns is probably in the sweet zone. best of luck. Jim
 
Does that carb have one or 2 adjustment screws??? I know the carb on my BA which is half B half A only has the idle screw and the man jet is fixed with no adjustment. I would start by pulling the carb drain plug and make sure you have a good steady flow of gas for a few minutes. Catch it to look for water/dirt etc. If it has the fixed man jet pull the cover off of it after checking the flow and make sure you have a steady flow out of it.
 
It is a Zenith with (1) screw. I drained the tank, removed/cleaned/replaced sediment bowl and screen (which was very clean) checked flow out of bowl, checked flow out of line and removed carb bowl drain and watched steady stream for over a minute.

I took carb apart again and removed everything I could remove, cleaned with carb aleaner and replaced. All the tiny holes in the jet were spotless.

It will now run without choke but barely, and I cannot get it to quit 'searching' as I call it. (Rum, Rum, Rum..., sounds like a Detroit 6V72 at idle).

I am STUMPED. I am thinking I did something wrong in carb, but what???
 
I re-read the thread about the Super C carb below. I tried all that as well. Used ether and no effect on idle. Checked manifold gaskets best i could and everything else i could think of.

Hmmmm...
 
Raise the float level 1/16" at a time to see if it affects the running richness. If it does, 1/8" is about all it can stand. If it is a little better, the issue may be that the main jet is just too small to pass enough E10 gasoline to keep it happy. Have someone drill out the jet (tiny amounts are so small that it takes a number drill to do it!!!! Be very careful to not take too much! Jim
 
You say you have good flow to the carb. You say you cleaned the carb just because you can blow air thru the idle circut doesent mean that passage is totaly clean. Mite need some small drill bits to get the bottom clean by turning them with your fingrs then rmoving you can sometimes see residue on the tip till you get that passage clean.Your problem is the fuel system. Is the aircleaner clean. Remove the hose to see if that helps engine run.
 
if you can try to get the main jet out if you take the 1/2 nut on the bottom its in there and will have a flat blade screwdriver head on it they like to get full of rust may have to heat some to get it out
 
Over the main jet is a cap plug. Remove it and see if you get a good steady flow of gas. I'll bet you do not get a good steady flow out of it. I clean that main jet out by turning off the gas then with the drain plug out spray carb cleaner into it and with a torch tip cleaner tool I poke that jet out real good then spray carb cleaner in a again
 
Please excuse my ignorance, but are you talking about the plug on the bottom of the carb that sits horizontally and faces the radiator?? Because I can find no other except the drain.
 
Yes that is the one. Under it is the main jet and I'll bet it is clogged up. You should be able to pull that plug turn on the gas and have a good steady flow of gas out of it. If you do not then you found the problem. And as I said you can clean that out like I said and have a good chance you will fix it. BTDT on many old fixed main jet carbs
 
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