Cub hard starting and missing

casefrank · Apr 22, 2012

Morning all, Iv"e got a "47 cub that I"m having problems with and need you-all best suggestions.

Have had mag rebuilt and has nice blue spark, carb rebuilt( not cleaned) new plugs imming set, and the following compression check

COLD
dry #1 95 #2 92 #3 92 #4 92
wet #1 110 #2 100 #3 110 #4 95
HOT
dry #1 85 #2 80 #3 80 #4 80
wet #1 90 #2 90 #3 90 #4 90

Sprayed starting fuild aroud carb and intake maniford no real change

So the big Question is is it time to do a rebuild
Valves and rings (maybe rebore) ??
Thanks Frank

El Toro · Apr 22, 2012

The compression readings look ok. Bring No1 piston near the radiator to TDC on the compression stroke and then remove the cap and see where your rotor is pointing. It should be at the No1 plug tower that's about 1 o'clock. Your plug wires need to be in this firing order on the cap.
2-1
4-3 As the rotor rotates CW.

Hold your your hand over the throat of the carb while a helper makes an attempt to start the engine. You need good manifold vacuum to suck that fuel into the engine. Disconnect the gas at the carb and see if there's a full stream of gas from the tank. Use a clean container to catch the gas. If this looks ok remove the tube fitting where the gas line connects and look for a screen behind the fitting that may be plugged. Hal

evilboweviel · Apr 22, 2012

adjust your valves as they are probably too tight
dump half a can of seafoam in the oil and the rest in the gas tank. work the cub with a belly mower a couple of times for an hour or more
then think about a rebuild as your compression is low
also check over on farmallcub.com for other ideas
good luck
Ron

Cub hard starting and missing

casefrank

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El Toro

Well-known Member

evilboweviel

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