Low End Knock ? Kohler CH 20

[GTSRider]

I am hearing a low end deep toned knock at idle.
Engine runs superb at full throttle.
This is from my 2003 3000 series Cub Cadet with the Kohler CH 20 engine,
with now 574 hr.s on clock.
Could this knock be a rod.... or something like a harmonic noise from the tractor somewhere ?
I don't remember hearing it before.
Has anyone ever experienced this , or are Kohler V-twins known for this ?
Pete

 

[RandyT]

Maybe a rod going bad but not likely. Another posibility is the Kohlers have had some problems with flat spotting the bottom of the hydraulic lifters that can cause a knock but would probably hear also at full throttle.

 

[GTSRider]

25 HRS. ago I put in new head gaskets... do I have to readjust lifters again, and what is the procedure ?
I guess the reality of it all is..... it is the end of the mowing season here in NY
and in the spring I will use it,as normal and see if noise gets worse....

 

[Ottis21609]

Take a long screwdriver and put it against the block somewhere near the crank. Put your ear against the end of the driver while the motor is running. If the motor has a rod knock you will know right away. If you have never done this give it a try. Think of it as a doctor using a stethoscope to listen to your heart. A rod knock is most certainly unmistakeable..... Unfortunately.

 

[GTSRider]

Thanks...I forgot about that old trick.
Years ago, I had an old Toyota that had a rod knock only at idle....
and it would go away at speed or load....this is the same...
engine is surprisingly smooth , and mechanically quiet at full throttle,
but bring it down to idle.... and it has that old tug boat sound...
a deep knock , knock knock sound..... not a tick tick tick sound a lifter
would make. If it is a rod ..... I will most likely run it till she goes...
because if you have been reading my posts , I've been working on this sucker outdoors for 2 months....
head gaskets , then crank seals, then when all back together governor
shaft seal went , and during replacement shaft fell into crank case , so entire
front crankcase had to be split... all this through sun, rain and snow !
Now a rod knock ! I just don't know what else could make that noise...unless something is a miss in the trannie ?

 

[Gator6x4]

Sounds like you have a rod problem. The Kohler CH 20 engine is a good engine. From your previous posts it sounds like the previous owner of your CH 20 spells "use" the way a lot of people do "ABUSE".

If it is a rod knocking as you suspect it will not be long before it will destroy the engine. Things will then get expensive. New rods will cost less that one hundred dollars. Rods, Pistons and rings will cost a couple of hundred.

One good thing since you have already replaced the seals you can remove the front of the engine, the heads and push the pistons out. If you decide to do this please keep in mind, on the top of each piston is an arrow, it is pointed towards the flywheel. Each piston and rod is numbered for the coorsponding piston bore, either 1 or 2. Each rod also has a certain postion to face on the crankshaft.

The valve adjustment is pretty simple, leave the push rods out from under neath the rocker arms and then tighten the rocker arm retaining nut down(I, quoting from memory think it is 20 foot pounds) then rotate the crankshaft and using a fabricated tool lift the rocker arm, forcing the valve down and open and slide the push rod under the rocker arm, release the rocker arm and proceed to the next valve. The engine only has four.

I would not continuie to run the engine with it knocking unless I wanted to replace the engine.

 

[GTSRider]

I guess I never should have bought this one.... it had the abused look when I picked it up... time would show me just how much abuse it had .
One of the first things I did to it when I got it was to clean the engine
of debris and crud. The grass clippings by this time had turned to a cork like fiber....very dense and strong.... would snap in your fingers when broke in two.
The heads and fins were full of this crap. This engine may hold a world
record for the hottest oil temps.
I am not sure what I will do at this point... Gator...you are saying I could
pull rods...working from front, with cover removed and heads off ?
Next question is how many rod knocks have you heard of on Command
V -twins..... I take it this is rare and only happens with highly abused engines such as this one ?
Pete

 

[Gator6x4]

I know you advised you got creative when retrieving the governor shaft and did not completely remove the front of the engine. In this, did you have a shiny metal disk left over. There is a shim on the front of the camshaft to prevent the cam from moving back and forward when running. If the shim is left out the camshaft moving back and forward will also produce a low rpm knock. The old flat head Chrysler products with a six cylinder engine were famous for this.

And yes the rods and pistons can be removed by removing the heads and the front of the engine. Mark the rod caps and rods prior to starting removal. Do not re-install the wrong head on the wrong cylinder. The heads are marked but to be safe also mark them. The tops of the pistons have an arrow on them that is pointing towards to flywheel. Look for the arrow if you do not see make your own so you can get the piston re-installed correctly.

Also pay close attention to the rod caps prior to removal. They each have a side that must face one another.

 

[GTSRider]

Interesting.... I did not have any parts left over, and did thoroughly
clean inside crankcase as well as I could. I remember the centrifugal
wheel... the governor shaft rested against.... but no disc.
Where was disc located ?
But having said that.... I ran her for 2 hrs. straight yesterday, and she runs strong , and smooth.... I'm thinking this dull thud sound ...more than a knock
sound , is something other than a rod. I know a rod knock sound....
this sound does not seem to have the metalic sound....it's more like a low dull
thud , thud, thud sound.... and seems to be coming from the bottom end some where. Another thought I am having is that because I am listening to the engine like never before..... because I spent close to 2 months working on it
outdoors.........that I am being too critical, and all may be normal.
This happens when one is overly critical about every sound.
I know these engines are not as quiet as liquid cool engines....
but do they emit a rhythmic thumb sound from bottom end ?

 

[Gator6x4]

The spacer or disc I am talking about is on the end of the camshaft that fits into the front engine plate.