Piston damage ?

[Wheelhorse#1 1,667]

Bought this ole k-321 .Just getting started on dismantling it.So far it has a blown head gasket and a breaker less ignition.It has no spark so I’m going to put points in it.

The piston is pretty tight in the cylinder  with very little play, if any at all

 

should I  be concerned with the damage on top of the piston.Possibly someone use the wrong spark plug ? Haven’t seen this before .

 

[Howie 886]

That thing probably had a screw from the carb go thru it! Smooth it up

and use it if ringlands are ok.

[Achto 27,602]

3 minutes ago, Wheelhorse#1 said:

should I  be concerned with the damage on top of the piston.Possibly someone use the wrong spark plug ?

 

The spark plug does not sit over the piston on a flat head engine. It does look like something did take a ride in there though. I would not be afraid to use the piston the way it is.

[Wheelhorse#1 1,667]

21 minutes ago, Achto said:

 

The spark plug does not sit over the piston on a flat head engine. 

 
Great point ! And so ,there goes my theory . Thanks for the advice.

 

[Wheelhorse#1 1,667]

31 minutes ago, Howie said:

That thing probably had a screw from the carb go thru it!

Funny you mentioned that cause this screw is missing 

[kpinnc 12,088]

1 hour ago, Wheelhorse#1 said:

Funny you mentioned that cause this screw is missing

 

Was gonna say- the brass screw in the carb won't do that. Had one get into a new rebuild myself, and it got squashed flat without damaging the piston.

But those steel screws could definitely do it! Does your muffler have a rattle in it? 

 

I would say if the piston has no cracks, it should be ok to use it. Smooth the gouges out if you can, but don't grind too much. Knock off any high spots, use a shop vac to get all the metal out from around the cylinder, and put it back to work.

Edited August 12, 2021 by kpinnc

[roadapples 6,983]

I always locktite those screws. In fact one I put studs in with locktite and used nylock nuts...

[richmondred01 2,237]

Like Howie said, it’s the screw from the carb. It happens frequently. Not a big deal. Just check your cylinder walls for potential damage of that screw getting pulverized over the years and tiny pieces making their way into the cylinder.
As roadapples stated, locktite the new screw. 
You should be good to go. 

[lynnmor 7,308]

While it is apart, I would pull the valves and check to see if the junk that passed thru did any damage to the valves or seats.

[richmondred01 2,237]

1 minute ago, lynnmor said:

While it is apart, I would pull the valves and check to see if the junk that passed thru did any damage to the valves or seats.

excellent point. 

[pacer 3,173]

12 hours ago, roadapples said:

I put studs in with locktite and used nylock nuts...

 

1 hour ago, lynnmor said:

did any damage to the valves or seat

 

Both excellent suggestions......  I have an Onan and one of those dang things has come loose about 3 times (luckily on the Onan they had a valve close on it with no damage) I had added 10-32 socket head screws, replacing the flat driver heads so I could get better torque which did help, but.... I was doing some routine maintenance couple wks ago and ckd them and doggone if 2 of the 3 were loose!! This time I loctited them! If it happens again the studs method will be tried.

[roadapples 6,983]

The studs I used were Allen or hex with no head so the nut would go on. Guess you call that set screws  about 3/4" long I  think...

    Also once the studs are in there's less chance of stripping the threads in the carb from over tightening. Don't ask how I know 

Edited August 12, 2021 by roadapples

[pacer 3,173]

3 hours ago, roadapples said:

stripping the threads in the carb from over tightening

Thats always been my biggest worry, I cringe when I get at that last 'tweak' That 'pot metal' (Zamack?) theyre made of is .... somewhat .. brittle?

[Wheelhorse#1 1,667]

Thanks for the suggestions.I will definitely lock tight the screws in when I put them back in.

Ill be taking off the valve cover tomorrow to have a look at them and see if they are in spec.
All in all this motor looks pretty good so far and didn’t notice any sparkles in the oil.I’ll be pulling the bearing plate to have a look at the crank etc.and replace the seals and all gaskets.

This is my first Kohler, it sure has been a pleasure to work on.

Edited August 13, 2021 by Wheelhorse#1

[Gregor 4,846]

On 8/11/2021 at 10:16 PM, kpinnc said:

the brass screw in the carb won't do that.

To quote my uncle Mike again; "I dunt agrrrree wit wat yer sayin', but I'll defend til dett, yer rrrright ta say it"

 

The bras screw from my butterfly plate definitely beat beat up my aluminum piston, and head.

[kpinnc 12,088]

21 minutes ago, Gregor said:

To quote my uncle Mike again; "I dunt agrrrree wit wat yer sayin', but I'll defend til dett, yer rrrright ta say it"

 

The bras screw from my butterfly plate definitely beat beat up my aluminum piston, and head.

 

Maybe mine was softer brass. It happened right after a carb rebuild, and the plate screws had been replaced. Or it may have something to do with the fact that I shut the engine down immediately when I heard the knocking. Either way, my engine was not damaged. I'm still using it now 10+ years later.

[Gregor 4,846]

19 minutes ago, kpinnc said:

I'm still using it now 10+ years later.

I also removed the screw, replaced the gasket, and still running. I don't remember how long ago, but 7 - 8 years anyway.

[kpinnc 12,088]

Sounds like we both were lucky. Somehow I doubt anything newer would have survived injesting much more than dust.

[Wheelhorse#1 1,667]

Well I remove the valve cover and inspected the valves .No screw or damage anywhere.I checked the gap and they were in spec.

pulled the oil pan too and nothing but a little muck at the bottom.

By eye everything looks good, nothing loose or broken gears.Looks like the balance gears are missing , is that right ?