Bubbling around spark plug

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charris135
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Joined: Sun Mar 21, 2021 6:47 pm
Zip Code: 23061

Bubbling around spark plug

Postby charris135 » Fri Apr 16, 2021 8:36 am

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
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Re: Bubbling around spark plug

Postby tst » Fri Apr 16, 2021 8:48 am

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
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Re: Bubbling around spark plug

Postby john2189 » Fri Apr 16, 2021 9:47 am

What about the sighing? Both my 72 and 49 sighs when I shut them off, sorta like sigh, finally i can rest.
John
'49 Cub (Vince)
'72 cub (Cecilia)
'41 allis B
'42 Allis B
'71 154 Cub Lo-Boy
656 Wheel Horse with 42” sickle mower
C-165 Wheel Horse
Simplicity 20 HP Sunstar
Honda 48” walk behind mower

Eugene
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Re: Bubbling around spark plug

Postby Eugene » Fri Apr 16, 2021 10:47 am

john2189 wrote: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.
I have an excuse. CRS.

john2189
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Re: Bubbling around spark plug

Postby john2189 » Fri Apr 16, 2021 12:28 pm

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?
'49 Cub (Vince)
'72 cub (Cecilia)
'41 allis B
'42 Allis B
'71 154 Cub Lo-Boy
656 Wheel Horse with 42” sickle mower
C-165 Wheel Horse
Simplicity 20 HP Sunstar
Honda 48” walk behind mower

SamsFarm
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Tractors Owned: 1968 Cub Fast Hitch
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144 Cultivators
L-F194 Plow(s)
F38 Disk
L-F3 Spring Tooth Harrow
Fast Hitch CS Bell 60 Grain Mill
Home Made Fast Hitch Potato Plow
54A Blade

Couple 1948 Cubs
172 Runner Planter
53 Fertilizer
Cub-3 Field Cultivator
Cub-189 Two Way Plow
Cub-22 Sickle Bar Mower
Mechanical Transplanter with side mount barrel (needs a fast hitch adapter) :)

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Location: Ne Ohio

Re: Bubbling around spark plug

Postby SamsFarm » Fri Apr 16, 2021 2:15 pm

john2189 wrote: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!
1968 Cub fast hitch

Clemsonfor
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Re: Bubbling around spark plug

Postby Clemsonfor » Fri Apr 16, 2021 4:12 pm

SamsFarm wrote:
john2189 wrote: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
501 Club
501 Club
Posts: 850
Joined: Wed Jan 20, 2021 8:21 pm
Zip Code: 44410
Tractors Owned: 1968 Cub Fast Hitch
LF-1 Platform Carrier
144 Cultivators
L-F194 Plow(s)
F38 Disk
L-F3 Spring Tooth Harrow
Fast Hitch CS Bell 60 Grain Mill
Home Made Fast Hitch Potato Plow
54A Blade

Couple 1948 Cubs
172 Runner Planter
53 Fertilizer
Cub-3 Field Cultivator
Cub-189 Two Way Plow
Cub-22 Sickle Bar Mower
Mechanical Transplanter with side mount barrel (needs a fast hitch adapter) :)

Misc Belly Mowers

Wish List
International 100 Fast Hitch Blade
Mott Fast Hitch Flail Mower

Wish Wish Wish List
Fast Hitch Rotary Hoe
4E hammer mill
Location: Ne Ohio

Re: Bubbling around spark plug

Postby SamsFarm » Fri Apr 16, 2021 4:37 pm

Clemsonfor wrote: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! :)
1968 Cub fast hitch

john2189
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Re: Bubbling around spark plug

Postby john2189 » Fri Apr 16, 2021 5:16 pm

Sorry I should have started a new post
'49 Cub (Vince)
'72 cub (Cecilia)
'41 allis B
'42 Allis B
'71 154 Cub Lo-Boy
656 Wheel Horse with 42” sickle mower
C-165 Wheel Horse
Simplicity 20 HP Sunstar
Honda 48” walk behind mower

Eugene
Team Cub Mentor
Team Cub Mentor
Posts: 19266
Joined: Fri Jul 02, 2004 9:52 pm
Zip Code: 65051
Circle of Safety: Y
Location: Mo. Linn

Re: Bubbling around spark plug

Postby Eugene » Fri Apr 16, 2021 7:26 pm

charris135 wrote: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.

john2189 wrote:What about the sighing? Both my 72 and 49 sighs when I shut them off, sorta like sigh, finally i can rest.

Clemsonfor wrote: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.
I have an excuse. CRS.

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Glen
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Re: Bubbling around spark plug

Postby Glen » Fri Apr 16, 2021 8:47 pm

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. :)


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