carb question

[bentfork]

My 52 cub has a funny habit of not starting unless I hold my hand over the air intake while cranking it over? what could be causing this?

[Don McCombs]

Do you use the choke when starting? Have you checked to see whether the choke is working properly?

[bentfork]

yes the choke is opening and closing properly... I have tried staring with and without the choke. holding my hand over the carb air intake is the only thing that works....im stumped

[Don McCombs]

OK. Here's my thinking out loud. Given that the choke seems to have no effect on the outcome, my guess would be that the engine is getting too little fuel to start properly. In other words, too much air. Covering the air intake reduces the air and it starts (and I assume continues to run properly, since you didn't indicate otherwise). I would look for one or more of the following...

Loose, broken or missing gasket between carb and manifold. This could also be the result of a warped carb manifold flange.
Loose, broken or missing manifold gasket.
Hole in intake portion of the manifold.
Worn or missing felt seals in the throttle body portion of the carb.
Loose, broken or missing gasket between the two carburetor halves. This could also be the result of a warped carb top.

Let us know what you find.

[bentfork]

ok thanks i'll check that stuff out

[CraigKennedy]

be sure to check your governor rod to the the carb, make sure it is not loose, theres a flat head screw on the carb end that tightens it, screw your fuel adjustment screw (on the back of the carb) all the way in, then back out 1 full turn
hope this helps,
-Craig

[RaymondDurban]

be sure to check your governor rod to the the carb, make sure it is not loose, theres a flat head screw on the carb end that tightens it,...

The screw behind the carb on the throttle butterfly will not "tighten" the governor rod. It is for setting the idle speed only.

.... screw your fuel adjustment screw (on the back of the carb) all the way in, then back out 1 full turn...

This screw only effects the idle air/fuel mixture.

[CSA_CUB]

I'd lie to know the compression on the engine. If it is low the vacuum created on the intake stroke would be less as well on the slow spin for cranking, thus requiring a complete shut off of air to pull the fuel out of the bowl. Once it starts the engine speed creates the vacuum needed to pull the fuel up the metering jet.

[Eugene]

Don McCombs list, previous posting, is very good.

The low speed/idle circuit in the carburetor maybe be plugged.