Bubbling around spark plug

[charris135]

Hi folks, as the title says I am noticing some bubbling around spark plug #1. When I was changing the plugs, this particular plug was a beast to get out. The threads were heavily rusted( the tractor had been sitting for a long time). I'm wondering if this bubbling could be attributed to the threads and their (poor?) condition. I've also noticed some skipping at low idle, and a sort of *sighing* sound when I turn the engine off. I don't know if this is related or if it might be a separate concern. Any thoughts on this situation and if there is a remedy are much appreciated.

[tst]

the plug is not seated, the surface of the hole in the head is all rusted most likely so the plug cannot be fully tightened, clean the rust from the seat, if you have a 18 mm tap clean the thread plug threads also, a dab of never seize on the plug when you put it back in, sometimes old washers are still stuck to the head also

[john2189]

What about the sighing? Both my 72 and 49 sighs when I shut them off, sorta like sigh, finally i can rest.
John

[Eugene]

What about the sighing? Both my 72 and 49 sighs when I shut them off, sorta like sigh, finally i can rest.

Sigh is compression pressure excaping a cylinder. Generally from a not fully closed valve.

[john2189]

Ok I adjusted the valves in the 72 a couple years ago. I’ll check them again.
If they are not sealing all the way, will they burn?

[SamsFarm]

Ok I adjusted the valves in the 72 a couple years ago. I’ll check them again.
If they are not sealing all the way, will they burn?

Eugene is not necessarily saying that your valves are not sealing all the way!

When your engine is shut off and comes to rest 1 or more of your valves will be in some sort of open position, that is just the way it is!

Your spark plug was bubbling because it was not seated properly!

You could do a compression test. Just a thought to see if maybe you have a bent valve, worn rings, etc.

If by chance you have a valve not seating all the way, you could adjust the valve clearance, and it would never help!


Have a great day!

[Clemsonfor]

Ok I adjusted the valves in the 72 a couple years ago. I’ll check them again.
If they are not sealing all the way, will they burn?

Eugene is not necessarily saying that your valves are not sealing all the way!

When your engine is shut off and comes to rest 1 or more of your valves will be in some sort of open position, that is just the way it is!

Your spark plug was bubbling because it was not seated properly!

You could do a compression test. Just a thought to see if maybe you have a bent valve, worn rings, etc.

If by chance you have a valve not seating all the way, you could adjust the valve clearance, and it would never help!


Have a great day!

This is two different guys? The bubbling plug guy is the original poster (OP). John is a different poster who's tractor also "sighs" when he shuts it off.

[SamsFarm]

This is two different guys? The bubbling plug guy is the original poster (OP). John is a different poster who's tractor also "sighs" when he shuts it off.

Oops!

[john2189]

Sorry I should have started a new post

[Eugene]

I've also noticed some skipping at low idle, and a sort of *sighing* sound when I turn the engine off. I don't know if this is related or if it might be a separate concern. Any thoughts on this situation and if there is a remedy are much appreciated.

What about the sighing? Both my 72 and 49 sighs when I shut them off, sorta like sigh, finally i can rest.

This is two different guys? The bubbling plug guy is the original poster (OP). John is a different poster who's tractor also "sighs" when he shuts it off.

I think we answered both individuals questions.

Most likely cause of the sighing sound is valve overlap.

[Glen]

Hi,
The spark plugs are supposed to have gaskets where they tighten against the head.

Try moving the throttle to the slow idle position before shutting off the engine, if you don't do that.

Slow idle should be about 500 RPM. If the slow idle speed is set too fast, it would still go faster than slow idle, when the throttle lever is to the rear.