Do I have a leaky head gasket?

[jonrick]

New OEM gasket ordered. In the mean time I'll pull the head and see how things look. Crossing my fingers it's not cracked!

 

[HKCooper44]

I've always installed the bolts dry after cleaning up the threads. But if you lube them up, a few drops of engine oil will do. Or spray them with silicon. If all you have is WD, go for it.

 

[jonrick]

Hold on! New heads are expensive, not to mention hard to find! Try this: pull the plug wire off and have someone crank the engine while you look and listen right at the head. Do you hear a "pfft, pfft"? Try to tighten the head bolts, especially the ones forward on the head. A bit loose? There you go! Remove the head. Keep track of what bolt came from what hole. Dust the mating surface with a bit of Krylon, then run the head back and forth on some medium sandpaper on a flat surface (like a kitchen counter when the wife's not around). This may take some time and elbow grease! Keep at it until all the paint is gone. Now, blow out all the bolt holes in the block with compressed air. Run a tap in the holes, if you have one. Put the head with a new gasket on the block. Wire brush the bolt threads and install each bolt dry with a plain washer (like an AN 960) and an internal star washer under the bolt heads (like an AN 936A). Torque the bolts in a star pattern to about 28 - 30 ft. lbs. This should fix the issue!

Is re-tapping the bolt threads critical? Only reason I ask is that I don't have the tools yet. My wife and I are in our 20s and still both paying tuition right now haha. I view this tractor as an investment that I want to last me, but I if can get away with just socket set/wrench stuff for now that'd be ideal.

 

[Doug Rusk]

Doubtful the head will be cracked, but anything is possible. More likely to be slightly eroded from hot gasses from the engine running where the gasket is blown. That is if it's been ran like that for any length of time.

That's one reason to use the sandpaper and glass trick, to make sure any potential damage or warpage is flattened back out so head will seal correctly.

 

[mgonitzke]

Please excuse my ignorance if this is a stupid question: Would some regular engine oil suffice or would something like WD-40 be better?

Oil or Anti-Seize. Latter is my preference to avoid future issues next time the head has to come off.

WD-40 isn't much of a lubricant once the carrier fluid evaporates. Only thing it works good for is a cutting lube for aluminum.

 

[mgonitzke]

Is re-tapping the bolt threads critical? Only reason I ask is that I don't have the tools yet. My wife and I are in our 20s and still both paying tuition right now haha. I view this tractor as an investment that I want to last me, but I if can get away with just socket set/wrench stuff for now that'd be ideal.

If the bolts thread nicely in by hand, no, but likely the holes near the exhaust valve will be carboned up.

You don't need a whole tap and die set to do this though. An individual 3/8-16 tap will be a few dollars at any hardware store.

 

[glippert]

Please excuse my ignorance if this is a stupid question: Would some regular engine oil suffice or would something like WD-40 be better?

Regular engine oil.

 

[-CӞ]

Tip I learned from my pa-in-law: when applying lube to threads, use a small hobby paintbrush 🖌
It allows for precision application and minimizes mess / waste, be it engine oil WD40 or light machine oil.
I use a small cup (repurposed spraypaint lid) to hold the oil/WD and load the brush and catch any drips before they ever leave the cup.

 

[dsarow]

jonrick
Hope you've making progress on your head gasket issue.Here is the site that I get my Rethreading Taps and Dies from.Its -Jawco.com.You can build a set for your Cub,reasonably priced.I recommend. A tap cuts threads in a hole,a rethreader kind of just moves and adjusts the threads as needed without removing.Much less aggressive, but works well.Like Matt expertly said you can get a tap at a hardware store.Always hand thread your fasteners,you can tell by the feel if the thread is acceptable, good luck!Pictures and questions?A great wealth of knowledge here!!!!

 

[jonrick]

I finally got the head off. USPS lost the new gasket and I didn't want the tractor apart for too long since it's not in an ideal location for working on it. I'm guessing at this point it is warped as per what a lot of you guys suggested. The gasket looks almost new. You can definetely see where it was leaking though. Here are some pictures:

 

[jonrick]

I noticed quite a bit of carbon build-up on the piston and valves. Will a leak cause incomplete combustion and result in that build up?

 

[mgonitzke]

Show us a pic of the piston and valves. Lots of different things will cause that. One is that the head may not have been off in awhile and all of that cleaned up. You are supposed to remove the head periodically and decarbon everything.

This would be a good time to remove the valves, clean them, lap them, and readjust them while you have the head off.

 

[dschwandt]

NAPA should have, or be able to get a head gasket for you.
Our stores around here stock them.

 

[jonrick]

NAPA should have, or be able to get a head gasket for you.
Our stores around here stock them.

Good to know! That would have been a lot more convenient haha.

 

[jonrick]

Show us a pic of the piston and valves. Lots of different things will cause that. One is that the head may not have been off in awhile and all of that cleaned up. You are supposed to remove the head periodically and decarbon everything.

This would be a good time to remove the valves, clean them, lap them, and readjust them while you have the head off.

I'll snap one this afternoon. Unfortunately I did already start cleaning up the cylinder, but the valves should give a good idea of how carbonized it is.

 

[jonrick]

jonrick
Hope you've making progress on your head gasket issue.Here is the site that I get my Rethreading Taps and Dies from.Its -Jawco.com.You can build a set for your Cub,reasonably priced.I recommend. A tap cuts threads in a hole,a rethreader kind of just moves and adjusts the threads as needed without removing.Much less aggressive, but works well.Like Matt expertly said you can get a tap at a hardware store.Always hand thread your fasteners,you can tell by the feel if the thread is acceptable, good luck!Pictures and questions?A great wealth of knowledge here!!!!

Thank you for the site! I definitely will need to acquire a set at some point. I'd like to go through the whole tractor shy of a rebuild once I get the space.

 

[jonrick]

I flattened the head with the tile and sandpaper trick suggested by you gentlemen, got the new gasket and head torqued down to spec today and fired her up. It appears to have fixed the head leak. Thank you to everyone who helped me by providing your input. I'm grateful for the new knowledge! The engine is still running a bit "off." But I think that discussion is likely a candidate for a new thread.

 

[HKCooper44]

If I was messing with the engine, I'd get the engine up to operating temperature, then set the throttle at a fast idle and adjust the idle speed screw 1 1/2 turns out from the seat. Then I'd add about 3/4 throttle and set the main fuel needle 2 1/2 turns out from the seat. That adjustment might have to be slightly adjusted either in or out to get the best RPM. Then see how the engine operates in use. That's about all you can do without digging further into the engine or carb.
Don't forget to check-tighten the head bolts from time to time. The 2 or 3 most forward bolts have a tendency to loosen over time.

 

[jonrick]

If I was messing with the engine, I'd get the engine up to operating temperature, then set the throttle at a fast idle and adjust the idle speed screw 1 1/2 turns out from the seat. Then I'd add about 3/4 throttle and set the main fuel needle 2 1/2 turns out from the seat. That adjustment might have to be slightly adjusted either in or out to get the best RPM. Then see how the engine operates in use. That's about all you can do without digging further into the engine or carb.
Don't forget to check-tighten the head bolts from time to time. The 2 or 3 most forward bolts have a tendency to loosen over time.

Do kohler carbs have transition jets? The best way I can describe the symptom is that it behaves like a car/truck carb that has a bad accelerator pump. When I throttle up from idle it stumbles. Sitting at mid throttle I can see the governor arm "hunting." Throttling up from mid-throttle no more stumble. Full throttle it smooths right out and is happy. The previous owner said he went through the carb and rebuilt and tuned it. I also have a video of start-up and different engine speeds.

 

[HKCooper44]

Nope. Walbro only has the idle jet and the main. No accelerator pump or power valve.