surging motor

Sun Jan 05, 2014 8:37 pm

Hey guys,
Once again i am hunting everyone expertise on cubs. My cub was surging at full throttle, after a while it would idle out , but then start surging again when put under a load. I adjust the governor linkage where it attaches to the carb, and it took out the surge but took away the ability to adjust idle thru the throttle lever. Any suggestions would be great and if it something that you may have a diagram to represent the adjustment would be great, if not I will try to dig thru my manuals. Sorry to be a beginner but I am trying to learn on the fly.
Thanks,
Larry 51' Farmall cub

Re: surging motor

Sun Jan 05, 2014 8:57 pm

Surging is usually an indication of low or reduced fuel flow - - - and or slight mismatch on governor linkage.

Having read the initial post several times, suggest putting the governor linkage to carburetor back to it's initial position. Then check the fuel flow through the carburetor, main jet for partial blockage, fuel level in carburetor bowl - - - basically make sure the carburetor is up to snuff.

Re: surging motor

Mon Jan 06, 2014 12:03 pm

Just a thought, but related to fuel is the gasket between the carb and the manifold. If it's not sealed well, the engine is sucking air in and causing the governor to adjust due to too lean fuel/air mixture.

Re: surging motor

Mon Jan 06, 2014 12:34 pm

To test the gasket leak , with the engine running , put the nozzle of a propane torch near the gasket surfaces and open the torch valve if you have an air leak the engine will change ie smooth out / rev slightly. This test will work around the intake manifold also.

Berlin

Re: surging motor

Mon Jan 06, 2014 12:47 pm

Bezirk wrote:To test the gasket leak , with the engine running , put the nozzle of a propane torch near the gasket surfaces and open the torch valve if you have an air leak the engine will change ie smooth out / rev slightly. This test will work around the intake manifold also.

Berlin


PS Don't light the torch. :roll: :roll: Grump

Re: surging motor

Mon Jan 06, 2014 1:41 pm

The torch test works better if you loosen and remove the fan belt from the crankshaft pulley so the air does not blow the propane away. Another possibility would be to cover the front of the radiator to reduce the air flow.

Re: surging motor

Mon Jan 06, 2014 4:40 pm

I had the same "surging problem" yersterday , +15 Deg.s , snowing and blowing snow , at the higher RPM's , I just figured that was the carb freezing up , with the moist, very cold air it was "ingesting ! A frozen carb would reduce the fuel supply when it was needed more , at the higher RPM's ! The "prop. air crafts" get into the same issues under cold moist conditions !
Just my thoughts, Lee Petrie, Joliet , IL - 9.6 Deg.s outside, right now in the Chicagoland area @ 3:30 PM Monday 1-6-14