Rough running M

[Dr. Bert]

Can"t get my M to settle down and run smoothly. I have boiled out the carburetor twice, added a new gasket and needle and seat. Adjusted the float level and cleaned all the orifices. Changed carburetors, no change. Adjusted the govenor, replaced all the spark plug wires, Checked the magneto--hot and blue, cleaned the spark plugs, ran a compression test--105 to 110 pounds, adjusted the valves, and I still can"t get the engine to idle smoothly. At half throttle and above it does better, but still has a miss. When under a load the engine smooths out, but still isn"t right. Any help or suggestions greatly appreciated. Thanks

 

[rustyfarmall]

Possibly the ignition timing is too far advanced, or you may possibly have a bad gasket or two between the manifold and the head.

Another thought, are you checking and setting the valve gap while the engine is hot, or when it is cool? Set the valve gap at about 0.020" to 0.022" with the engine just warm and you should be in the ball-park.

 

[Tom43]

Spray carburetor cleaner at the joint between the carburetor and the manifold and also the joint between the intake and head and see if the speed changes. If you slightly apply the choke does it smooth out any?

 

[Charlie M]

I'd also look for a hole in the intake side of the manifold.

 

[Anonymous-0]

Gentlemen: I have sprayed WD-40 around the intake manifold with no effect. Have not tried carb cleaner or ether. Valves set at 22/1000 cold. When I first started, pulling the choke part way out helped--that is why I focused on the carburetor--- now it simply loads up the engine. Thanks for the responses.

 

[Brissco]

Did you change distributer Cap and Rotor? Brissco

 

[Anonymous-0]

I have not replaced the dist. cap and rotor yet. Did examine them and cleaned them. New ones are about a weeks wait in this little cowtown. Guys-- I have a theory--I recall that when running the compression tests--one cylinder only recorded about 60 pounds on the first compression--the other were 75-80. I wonder if I have a valve not seating properly and at low RPM the loss of compression is more noticable than at higher revs., thus the sputter in the exhaust. What do you think? Will try the the cap and rotor replacement and if that doesn't help --I'm going to pull the head.

 

[Brissco]

Been thinking about your problem. Carb. seems to be elimanated, on the Mag cover Hairline carbon streaks can build up over time and cause leakage. It would be good if possible to have a mechanic hook up a automotive anayalizer and look at the firing with the engine running. If thats perfect ,you may have to have the Head removed and magnifluxed for a crack. An old IH mechanic told me one time, "Many of the M,s have cracked heads and the owners have no clue."Also you could have the valves done and install a new head gasket. Brissco

 

[jonny2006]

it might be sucking in air through a warn out gasket or mabey there is a lose manifold bolt alowing it to run lean on 1 or 2 cynlinders. I like to take a garden hose while the engine is cold and running and run ot over the intke manifold if she puffs white you got a leak. DO NOT POUR WATER ON A HOT ENGINE EVER!!!