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I have been having issues with this engine. Changed flywheel shear key,,and had to glue flywheel magnets back on.

Then carb was letting gas into engine causing the start-up to be a terrible thing. Oil blowing out muffler and smoking badly.

Fixed all that,,and now it is knocking in the lower end on start-up. Clears up quickly and is hard to hear sometimes.

I know this is a pressurized oil system,,with a filter. And I think it is losing oil pressure causing this but is a little out side of my diagnosis. Was hoping someone could clear it up for me.

How could it be losing pressure?? Where??

My first John Deere STX 38. I am thinking this is not one of JD's best. I have found info on them where some say it is a great machine,,but most say a lemon with lots of problems.

I'm thinking of buying a hood for it tomorrow for $100,,,and a little worried about this investment. Other than this knock and a hood,,, its good to go.
 

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Lost oil pressure wont cause a knock on start up.

If you lose oil pressure while its running, the bearings run dry, metal wears away rapidly, and the increased clearance causes a knocking noise. But its a knock all the time, it never goes away, eventually the rod lets go.

Make sure all the engine mounting bolts are tight.

Make sure you have 10w30 oil in it
 

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Sometimes our 14 hp Kohler, CV 14S, same basic engine as yours, makes a nasty knocking sound when starting and when stopping. I contribute it to the compression release mechanism. Been doing it forever.

Walt Conner
 

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Discussion Starter #4
Lost oil pressure wont cause a knock on start up.

If you lose oil pressure while its running, the bearings run dry, metal wears away rapidly, and the increased clearance causes a knocking noise. But its a knock all the time, it never goes away, eventually the rod lets go.

Make sure all the engine mounting bolts are tight.

Make sure you have 10w30 oil in it
I will take a look at the bolts,,I think it has 10w 30 in it.
 

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Sometimes our 14 hp Kohler, CV 14S, same basic engine as yours, makes a nasty knocking sound when starting and when stopping. I contribute it to the compression release mechanism. Been doing it forever.

Walt Conner
I had a CH14S on a wheel horse classic that knocked hard on startup and shut down, like you could feel it hitting...never got worse, never got better, fired right up every time. Never opened it up...haha

I will tell you this, if you have alot of carbon on the piston, these things can detonate at low rpms it seems, seems to do it worse as the engine cranks and the choke is let off and the engine "catches".
 

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Discussion Starter #6
Update:: I changed the oil today,,,,thought I had done this when I bought it but I guess not. It's usually my first move and is a mistake on my part.

The oil was very thick,,looked clean but thick. Put some 10w30 in it and it started great,,no noise no smoke. I will be testing it again after its sits overnight,,it's on "watch"!! lol

Now all I need to do is to get the float seat to work. I have a gas shut-off on it now.
I bought the new needle and seat,,, just need to put it in.

With a new hood on it,,it's turning out to be a nice looking mower and is getting closer to being mechanically correct.
 

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Discussion Starter #7
I keep thinking I did change the oil before,,It is possible I put SAE30 in it,,but it looked too thick for that. It won't happen again.
 

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Yeah commands dont really like SAE30...its not going to hurt them, but they just arent big fans of the stuff....

a weak battery can make em start kinda funny too...
 

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Discussion Starter #9
I'm still having issues with this. lol

I changed the needle and seat,,I think it is working OK now,,,will let it sit over night and see if it starts OK. I can't think of any way ,other ,,to tell if it is shutting the gas off correctly.

Originally the flywheel pin was sheared. I changed it and found the flywheel magnets,,,loose on stator. I re-glued them.( believed to be fixed)

Then the carb was allowing gas into engine overnight and had a terrible start-up. (believed to be fixed now)

Then it was knocking on start-up. Changed to a thinner oil. (fixed)

Now when I shut it down,,,I swear I can hear the flywheel magnets slamming into each other. Loud clicking noise just as it stops!! It's either that or the flywheel is hitting the sear pin.(which I doubt)
And on start-up,,it starts immediately but is very slow on first couple of revolutions,,then catches up and runs fine. No noise,,just odd!!!

I going to tear it apart again and see what is going on,,might need a new flywheel.

This thing has been a pain. The guy I got it from,,tossed the hood,,literally!! And is why I had to buy a new one. lol

I am starting to see why now!!!

I going to win this battle,,, I might be broke,,but victory will be mine!!!lol
 

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What you are hearing is completely normal, its the compression release. The slow start up is the compression release not releasing till the prescribed rpm. When it reaches that rpm the release swings away and you get full compression. THe clacking is also just the mechanical compression release chattering.

100% normal when everything is working right, and seems like only kohler compression releases do this, but its normal.
 

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Discussion Starter #11
What you are hearing is completely normal, its the compression release. The slow start up is the compression release not releasing till the prescribed rpm. When it reaches that rpm the release swings away and you get full compression. THe clacking is also just the mechanical compression release chattering.

100% normal when everything is working right, and seems like only kohler compression releases do this, but its normal.
Well,,I did not expect that. It's a OK thing then. It's really not a awful sound and not something that jumps right out,,but I'm not used to these Kohlers.

I'll give it a shot and let it go,,as is ,,,,,,and see what happens. Thanks.
 

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Yep, its one of those things that the Vertical kohler tend to do, as well as some horizontals. They got a nasty noisy compression release, but it works as good or better than any other out there.
 

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Discussion Starter #13
I'm going to have another to compare it to ,,soon,,,,,by the end of the week or maybe even tomorrow.

I was talking to the parts guy and he brought up that he would sell me his,,,,he named a price and I took it,,,,,just need to find a time ,for it to work, for both of us.
Tomorrow or Thursday it is.

The complete machine!!! Twins!!!!
 

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Discussion Starter #14
Lost oil pressure wont cause a knock on start up.

If you lose oil pressure while its running, the bearings run dry, metal wears away rapidly, and the increased clearance causes a knocking noise. But its a knock all the time, it never goes away, eventually the rod lets go.

Make sure all the engine mounting bolts are tight.

Make sure you have 10w30 oil in it

RED:: You are da man!! I was in the garage tonight finishing up other stuff and just out of the blue I decided to go look at the engine bolts on this.

They were loose but,,,,,,,,,,, just loose enough to rattle if under pressure. And 1 is missing,,of the 4. Will check that out tomorrow to see if it broke off or just dropped out.

I have been fooled by this machine before,,but I started and stopped it several times after that,,and I heard nothing. Seemed much better.
 

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my craftsman knocks at idle only with the clutch out, you engage the clutch so the belt for the drive dont spin and it would stop ....... i think its the belt because it looks like total crud

but you are shaft driven i think so that may not apply to you
 

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Discussion Starter #16
Well,,I picked up another stx 38 today,,they are very close to the same. Have the same 12.5 Kohler. This guy heard me talking and buying parts for the one I have and said he has one that is runs great. (he works at JD dealer)

So I got it. It has more noises in the engine than the one I have.lol

Maybe I am being too picky with the little clicks in the Kohler engines. But Briggs don't have these sounds. Some on start-up ,,,some on shut down and some while running. Some ,,,very hard to hear.

RED: You tried to explain this to me,,,I'm starting to listen. Sometimes all I hear is click ,,click ,,click!!!!
 

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Command singles are noisy engines, mechanically.

The compression release is substantial and it is basically like a metal pin that is in one of the cam lobes and as the lifter is smoothly following the smooth cam, it hits that raised notch and it snaps the valve open for just an instant to bleed off compression, and the compression release itself is a heavy metal arm on the cam that, with centrifugal force, swings away, so it also makes some noise as it is operating.

As things wear, they make a little more noise than new...but Ive heard new engines chatter and clack and snap on start up and shut down.
 

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I had Command singles on several Ditch Witch trenchers, and I must say they were relatively trouble free. The only weak point was the mounting of the recoil starter to the blower housing. They do make some unusual noises when the CR is operating.
 
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