Carb ???

Sat Dec 20, 2003 12:03 pm

My cub will run great as long as I keep the choke closed a little, but when I open it all the way the engine starts cutting out. I have the float level set correctly and the carb has had a rebuild kit installed? Need advice!

Sat Dec 20, 2003 12:39 pm

It has to be one of two things. Either not enough fuel is getting to the carb, or too much air is getting to it.
You said you put a kit in the carb. You may need to clean it well like maybe soaking overnight in carb cleaner. Also, make sure the main jet is clean. Check the screen at the fuel line input and the flow from the tank. The excess air could come from poor gasket fit at the carb / manifold, or a leak somewhere in the manifold. You can rule out this by taking an unlit propane torch and moving the tip around anywhere air might get into the system. If the engine smooths out, you've found your leak.

Sat Dec 20, 2003 12:57 pm

Thanks for the advice BIGDOG. I did soak the carb overnight in carb cleaner. I'll check for vacuum leaks and proper gas supply.

Sat Dec 20, 2003 2:23 pm

You can also raise the float a little to see if that helps.

Tue Dec 23, 2003 5:41 pm

I had similar problems with my loboy. The problem was fuel flow from the tank thru the sediment bowl. Take the fuel line off the top of the carb and hold it over a coffee can or equiv. Then open the fuel valve at the sed bowl. It should really come out good. If it doesn't; or it slows down after a couple of seconds; there's something going on there. Mine had the screen missing(bout the size of a half-dollar) and gunk in the tank was clogging up the sediment bowl orifice and then also the main jet, which is only about .038" in diameter. I purchased a new one and have not had that problem since. Also, that your sediment bowl looks full is not a sure sign of proper fuel flow. Good luck.

Tue Dec 23, 2003 5:46 pm

Forgot to mention a couple of other things I remember from previous posts: If you have an INLINE filter it may be clogged and resisting the fuel flow.....and I remember a post about some types of fuel filters meant for pressurized systems will prevent proper fuel flow with the Cub's gravity feed system.

Tue Dec 23, 2003 7:38 pm

Thanks Marion (57 Loboy) and Bigdog for the info.
I think I've isolated some of my carb problems. First the fuel bowl had no screen at all and a inline filter has been added between the bowl and the carb. I disconnected the gas line from the carb and opened the fuel shut off valve on the bowl assembly. The fuel flow was some what weak. I'm going to purchase the screen for the bowl and remove the inline filter.

Thanks WCOX410