carb trouble

Wed Jul 07, 2004 4:05 pm

I was having some carb trouble at the beginning of the season.
The tank was full of crud and the bowl gasket had dissolved.
The cub would start but would shut down after a few minutes.

I gel coated the gas tank, installed a new sediment bowl and rebuilt the carb.
Put all the stuff together and away she went. Run fine for a few days.
I noticed a small leak that the petcock so I tightened the packing nut.
And that started all my trouble. With the gas system now sealed (air tight) the cub will start and shut down.

With the gas system sealed the sediment bowl fills really slowly.
If I remove the gas line the sediment bowl fills quickly
If I loosen up the packing nut and the gas system sucks air the sediment bowl fills quickly.
If I remove the bottom half of the carb and work the float the sediment bowl fills quickly.
It seams that when the gas system is closed (air tight) gas does not flow.
And if the gas system sucks air the sediment bowl will fill.
Is there a vent in the card the may be clogged?
There is not much hair left on my head to pull out.

Wed Jul 07, 2004 4:15 pm

Spaceghost: I had a similar problem on a Cub. I solved the problem by installing an in-line shut-off valve near the carb. I leave the valve at the sediment bowl open and shut off the gas near the carb. Works well for me. Dan

Wed Jul 07, 2004 4:44 pm

With everything tight (as it should be) gas will only flow as much as the needle valve will allow. Make sure the vent in your gas cap is open. Once the float chamber in the carb is filled, there should be adequate fuel flow as long as the tank is venting. I would expect the sediment bowl to fill slowly with no extra air getting into the system.