I'm stumped.

[FarmallAddict]

Sorry for all the posts. When I get a project going it's all I can think about. Especially if it involves old tractors.

My C continues to surge when not under load. Yesterday I took the governor cover off and to my surprise things looked very good inside. I believe someone has rebuilt this in the past, likely when it was repainted. No way all the internals are original when I compare it to some videos I've watched of other people's governor problems. The only thing that was obviously broken was the bumper spring which I replaced along with the other spring inside the case. No apparent wear on the spring arm holes or "fork" I guess is what I'm calling it. The other spring that pushes in the bushing for the weights looked essentially new so it couldn't be original. The thrust bearing looked great with no wear or any resistance. Again it looked as if it had been replaced at some point. The only worn part I could find might be the slight bit of play on the weight pins. They wobbled perhaps 1/16th of an inch or less so perhaps that is the issue? They appeared free and functioning correctly. The weights themselves were not worn or hung up at all.

I adjusted the carb/governor linkage per the service manual. I've cleaned the carb, put new plugs and distributor wires in. What could it be? Could a bad coil or rotor/distributor cause a sporadic miss and the governor is trying to adjust for it leading to the engine surging or skipping? I can hold the governor/carb linkage with my hand and it seems to help smooth things out a bit. I might need to have someone who knows more than me look at it. Throttle response is great, the engine doesn't smoke at all, it fires up immediately when I press the starter. It's frustrating to say the least that it won't quit surging.

[Eugene]

Could a bad coil or rotor/distributor cause a sporadic miss and the governor is trying to adjust for it leading to the engine surging or skipping?

Could be an ignition fault. Kinda far down my list of possible causes.

Timing light on each plug wire. Looking for a skip, or a plug firing slightly behind the timing mark.

Remember, we are trying to find the surging cause. If it is an ignition fault it could be anything; a worn cam lobe, worn bushings, malfunctioning advance.

[Eugene]

Everything looks good, last resort.

Governor Rod Linkage Spring. They were used by Allis Chalmers and are still used by many small engine manufacturers to reduce/eliminate surging.

[FarmallAddict]

I took it to a local tractor mechanic today and he adjusted the valves, put new points on it, and checked out the governor and carb. He held a paper towel over the exhaust and whenever the engine would surge/miss the towel would be momentarily sucked in to the exhaust pipe. He thought it could be a burned or sticking valve and the governor is trying to adjust for it every time it misses. Does that sound plausible? I think he said he adjusted the valves to .017". The engine was warm at the time.

Next I'll get a compression tester and see if that tells anything. If it's something like that then I'm pretty depressed about this actually and it's very discouraging.

If the head has to be re-done that's a minimum $500. I think I can do everything myself except machining the head and that gets really expensive. I guess I don't know for sure but things are pointing to the issue being inside the engine.

I need some advice on how to proceed besides the compression test I'll be doing later this week. This could be expensive in a hurry. Literally everything on the machine works great except for this surging/missing. I can look for one of the governor linkage springs to help alleviate some of the surging.

[FarmallAddict]

Everything looks good, last resort.

Governor Rod Linkage Spring. They were used by Allis Chalmers and are still used by many small engine manufacturers to reduce/eliminate surging.

I wanted to make sure I said thank you Eugene. You've responded to a few of my questions either here or on the Cub page and it is very much appreciated. I'm turning 30 this year so my wife suggested I buy this C because of how much I like old farmalls and I wanted a good chore tractor for odd jobs. It was sort of a birthday present I guess but with a practical purpose in mind. I also knew the previous owners well and they are very honest people so I think whatever is going on with this machine they didn't know about.

[Eugene]

He thought it could be a burned or sticking valve and the governor is trying to adjust for it every time it misses. Does that sound plausible?

Could be. Check for sticking valve(s). Remove the valve cover and spark plugs. Slowly turn engine over by hand. Check the valve stems to see if they rise to the same level as you rotate the engine.

While you are there, solvent on the valve stems.

Next I'll get a compression tester and see if that tells anything.

You need to have a compression tester. They will tell you a lot about the engine's over all health.

[FarmallAddict]

Any particular solvent you recommend?

[Eugene]

I use PB Blaster. Keep several spray cans on hand. Mainly because the auto parts store stocks it.

There are other good solvents. Just not WD40.

I would have thought that your mechanic would have noticed sticking valve(s) when he adjusted the tappet/valve gap. Or at least checked for it after noticing the missing exhaust stroke from the exhaust pipe.

Before you start tearing things apart, check the easy stuff first; ignition timing/fault and compression.

[Don McCombs]

Any particular solvent you recommend?

Kroil is another good one, but sometimes hard to find. Available online at Kano Labs.

[FarmallAddict]

Thanks I'll grab a couple cans of one or both of those and report back on the compression test results when I'm able. It's been unusually warm here and work has been keeping me from digging further into this project so far this week. I'll also check for a sticking valve while at at it. The tractor mechanic I normally prefer is backed up the rest of summer with work. This other guy I had never used before. To be fair he was trying to diagnose the machine while it was sitting on a trailer in 90 degree heat which we are not at all accustomed to in this part of the country. Stay tuned...

[FarmallAddict]

All four cylinders were between 118 and 121 pounds. I didn't believe it so I checked them twice. I didn't have time to pull the valve cover and check for sticking valves. Likely that will be this weekend.

[FarmallAddict]

One thing I noticed when cleaning the carb was the float doesn't have a lot of travel compared to the Briggs engines I've worked on. Could the float be closing the needle valve too quickly and the engine momentarily running out of fuel before it opens again? At this point I'm in full speculation mode.

If I start the tractor and disconnect the governor/carb linkage and control it by hand could that theoretically isolate the governor and tell me anything? If the engine runs smooth while I hold the carb linkage steady but the governor arm flutters wouldn't that mean it has to be the governor? I'd have my dad on standby to shut the machine off as a safety precaution. If it still runs like crap then it's either something with the fuel, the ignition system, or a sticking valve. I would have thought a burnt valve or blown head gasket would have shown up on the compression test. The results I got were not at all what I was expecting. I was expecting 80-90, not 120 pounds.

[FarmallAddict]

It was the engine timing. I took the tractor to the guy I really trust and within 10 minutes he had it figured out. I had tried tweaking the timing but he had the experience to get it right.