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Hi
I have a Cub Cadet LT1046 with a 23hp CV23S Kohler commander V-twin (Spec # 75604)
A couple of weeks ago I almost finished mowing my lower back yard, about 1.5 acres, when it suddenly stopped. After some trying it started again, but blew clouds of light blue smoke.
It also made a cracking noise, like something cracked/broke. Shut it down quick.

What I found/did so far:
Spark plugs look oily. Cleaned the plugs, I get a blue spark when I test them. It fires fine with fuel down the carby, so I assume spark is ok, at least short term.
Checked fuel line, pump & solenoid fuel to carby OK (actually now I think about it when removed solenoid, fuel runs out, so fuel getting through). Thoroughly cleaned carby - jets, float and all look ok.
Borrowed a compression tester and it tested at 165 and 175 psi - manual states 165 psi.
I did a bit of a DIY leakdown test using compressor. The only noticeable air is when I put my finger over the breather - after a short while I release it and some pressure has built up.
I put fuel down the carby again and it fires up for a few seconds, then stops. Blows a lot of blue smoke.
Someone suggested head gasket. Heads off - old head gaskets, reed valves look OK.
I tried with new gaskets first on 1, then on 2. It does not run for more than a few seconds with the new gaskets. Still blows smoke.
Took cylinder 2 head off again as it is now my hunch that it is the problem - has some oil in it.

So that's where I'm at. Need to find:
1. Cause of the crack sound, like metal snapping
2. Why won't start (without fuel down carby)
3. Clouds of smoke when I do start it

Any clues would be very helpful.
Thanks, Mark

Does you motor oil smell of fuel, is it over full?

Deerlane said:

Does you motor oil smell of fuel, is it over full?

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Thanks for responding.
I should have mentioned that. No, oil is normal and at correct level.
The mower has been well maintained. Had service about 6 hrs ago - oil, filters.

The bores look smooth, unmarked. The tops of pitons & heads have an even coating of carbon - as far as I can see nothing unusual.

check your breather assembly for dirt,could be a valve seal also

tybilly said:

check your breather assembly for dirt,could be a valve seal also

Click to expand...

Air filter, breather assembly are all off at present. Still smoking.

Could be valve seal. Don't have valve spring compressor, so haven't checked these. Would valve seals go suddenly? Would they make a crack noise?

BTW Engine did not overheat as far as I can tell.

sorry I should've been more specific,crankcase breather assembly,should be on top of your engine near the throttle control mechanism,another thing could be a worn out oil ring,...as my mentor once said..if its made by man its going to fail..lol

No expert here.
Is it the breather assembly that runs from tappet cover to air filter. air filter.is off, thus breather is off.

What is most likely? Valve seal or ring - with oil in cylinder & even coating of carbon on piston tops and heads.

Mark

A engine will run with out a oil ring.
You say it wont start and making a noise.
You are saying it wont start or run. But yet it smokes when put a little fuel down the carb and it tries to start.
Is it oil smoke or a rich fuel smoke?
There is a compression release on the cam making the noise in the case. If you have heads off crank engine over to see if noise in still there.
With heads on you can see the rockers dump compression on #2 cly if working proper. The rocker will move around .008, very little.
It all most sounds like two things going on.

Sounds like you need to tear it down and know what you are looking at.....

Many thanks for your help, much appreciated Deerlane.

Deerlane said:

Is it oil smoke or a rich fuel smoke?

Click to expand...

When I start it with fuel in the carby it could be I suppose. I'll take better note of the color when I do it next (head is off at present)

Deerlane said:

There is a compression release on the cam making the noise in the case. If you have heads off crank engine over to see if noise in still there.

Click to expand...

No haven't heard that noise since the first time I tried to restart it in the garden (it's now in garage)
When I turn it over there is no noise. So that could be it. If it is, is it anything to worry about?

Deerlane said:

It all most sounds like two things going on.

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Yes, it may well be. Something to do with 1. carby/manifold and 2. smoking.

I'm wondering if there is a small crack in the inlet manifold or something like that.

Are they prone to anything like this?

Here are some photos.
1. Gasket cy2
2. Head piston bore Cy2
3. Gasket cy1
4 Exhaust manifolds 1 & 2

With a blown head gasket the engine will still run with the other cyl. Look close on both sides on gasket from the piston to valve push rod hole in gasket, that's where #2 cyl will blow out the most. Mostly from the heat from the muffler close to the head.

The noise may have been the compression release stuck out or the engine run backwards like a dieseling.

I don't think this is it, but check you flywheel key to see if its sheared. I told a another gentleman to do this a day or two ago.

I still cant understand why it wont start or run, even if one of the cyl or head is bad.

I want to get this thing running, then worry about the smoke and noise.

The gaskets form what I see look fine. The second exh pipe looks a little more wet, maybe? #2?

Deerlane said:

I want to get this thing running, then worry about the smoke and noise.

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Yes, I agree. I was just thinking the same. Get it going then worry about the rest.

At first I was trying to do it all and ready to go. But that ain't going to happen in a hurry by the look of things.

So get it going first.

I'll revisit the fuel - manifold carby pump.
Maybe run some fuel through manifold see it it leaks.

Deerlane said:

A engine will run with out a oil ring.
You say it wont start and making a noise.
You are saying it wont start or run. But yet it smokes when put a little fuel down the carb and it tries to start.
Is it oil smoke or a rich fuel smoke?
There is a compression release on the cam making the noise in the case. If you have heads off crank engine over to see if noise in still there.
With heads on you can see the rockers dump compression on #2 cly if working proper. The rocker will move around .008, very little.
It all most sounds like two things going on.

Click to expand...

I didn't pay attention,I was addressing the blue smoke,lol

Deerlane said:

flywheel key to see if its sheared.

Click to expand...

quickly took bolt off and flywheel key looks ok - it's in place and straight, so I assume it's OK.

Called away for a trip interstate, so won't get back to it now for a few days.

Cheers...

Agree that it should still run on one cylinder. Most likely a fuel issue. Will somebody take a look at the picture of the head he posted. It looks to me like the exhaust valve is pulled down into the seat. Could it be possibly that this has been running on one cylinder for a while, and the good cylinder gave up the ghost.

Thanks for your help.

ILENGINE said:

Could it be possibly that this has been running on one cylinder for a while, and the good cylinder gave up the ghost.

Click to expand...

Has been running really well until this point. "Firing on all two" through thick and thin.

what? said:

Called away for a trip interstate, so won't get back to it now for a few days.

Click to expand...

Back again now, and getting frustrated.

Put a new carb on, new gasket. Carb and manifold torqued to correct specs.
New spark plugs, gap correct (just in case).
No go. Doesn't even cough.

A couple of attempts with fuel down carb. (it always fires with fuel down the carb)

Immediately after I had the fuel line off and retested that fuel was being pumped through.
Also noticed that the oil sentry wire was off at this point.
It did fire once of it's own volition and went for a few seconds (like 1, 2, 3 from exhaust)
But, have not been able to repeat this.

Checked fuses etc, all seem ok.

It has me completely beat now. What could it possibly be?

Quote, Checked fuel line, pump & solenoid fuel to carby OK (actually now I think about it when removed solenoid, fuel runs out, so fuel getting through). Thoroughly cleaned

The fuel solenoid is working?
Do you have power to the carb solenoid?
Did it come with a new carb or did you install the old one to the new carb?
Did you see it work or can you hear a click at the carb when ya just turn the key to run?
Did you check the fuel pump. Remove the fuel line from carb and crank engine over to see if it will pulse fuel.?

Thanks Deerlane.

QUOTE:
The fuel solenoid is working? Yes (but actually new carb does not have solenoid, just a plug)
Do you have power to the carb solenoid? Yes
Did it come with a new carb or did you install the old one to the new carb? Actually, went to buy a carb kit, but they didn't have another, so offered me a new carb
Did you see it work or can you hear a click at the carb when ya just turn the key to run? Yes, both.
Did you check the fuel pump. Remove the fuel line from carb and crank engine over to see if it will pulse fuel.? Yes, made sure it pumped enough to fill bowl in about 5 to 10 sec.

Makes me wonder, if the new carb does not have a solenoid, does the solenoid wire need to be connected?

(I do plan to put the solenoid on when I finish, as on an old mower the float valve leaked over time and filled the sump with fuel.)

If the carb just has a plug, the fuel solenoid wire can just stay unplugged. But if you install the solenoid, you must install the power wire.

Quote, Yes, made sure it pumped enough to fill bowl in about 5 to 10 sec. ( Is it Gas ) :ashamed:

:confused2: You are still not getting fuel to go into the carb from the pump :confused2:
Your sparks plugs are dry after a good 15 seconds of trying to start with full choke? Is your gas, good gas. LOL Maybe someone dumped water in your tank.

I thing we covered everything except choke, manifold leak, plug muffler, bad cam lobes. :mur:

"You are still not getting fuel to go into the carb from the pump"

Yes, must be as spark plugs have fuel on them after turning the engine over.

Rechecked stuff again. Compression, spark, fuel etc. All OK.

Set up a gravity feed for fuel to be sure.

When I put a teaspoon of fuel down the carb throat, it fired for a couple of strokes and seemed to tick over for a couple more. Sounded promising, but would not start again.

Wondering:
If it runs like this is it indicating that air is entering the system. i.e. it gets the 'rich' mixture straight down the carb, mixes with the air leak and it is then the right mixture and it fires.
But with air getting in the mixture is too lean.

Or could it be anything else.

So far:
Fresh fuel gravity fed bypassing tank and pump.
New carb.
New spark plugs.
Key OK.
Compression OK.
Spark OK - blue.
Plugs wet - so fuel to cylinders.
Tested magneto (as per manual) OK.
Kicks over with fuel down carb

So the plugs are getting fuel from the carb and pump. Also by a remote tank by gravity.

I would do this if you feel you can. Get a can of carb cleaner. Start engine with gas down the carb and then SHORT BURST of carb cleaner down the carb to keep the engine running for a 30 seconds or so. If you can, still have the fuel IV working. Make sure you do this outside.



I'm starting to get lost

Looks like I got it running. Took the manifold off (again) and carefully put gasket goo on the surfaces and re-tauqued it.

Hit the started and it ticked over - at last. Strange as it had new gaskets. But great news!!

Thanks everyone for your help, especially Deerlane.

Now I need help figuring the springs on the throttle/governor please.

The shorter spring. I didn't see where it came from when I disassembled. I thought I could figure it out, but it has me wondering. I can't seem to see where it goes. Any clues please?