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Hello Everyone, Hoping someone could help me on this issue!

I am at wits end with my Toro Recycler mower with a Kohler XT-675 engine on it. Currently this engine will spit oil (with velocity) out the crankcase breather which vents into the air filter box. Usually it puts enough oil in the air filter to fill the carburator and stall the engine. This ends up with either requiring a carb clean or a few week sit for most of it to drain back out and allow to start again. I have verified multiple times that oil level is within specs. For someone to visualize how much force the oil is being pushed with, you can imagine without the air filter on, the oil is propelled out the air box 1-2 feet away from the mower.

One thing I read online is the float in the carb may be stuck open thus causing the engine to flood and the oil to thin out raising the level higher and thus making it come out the breather tube on the crankcase. I have rebuilt the carb and it is still having oil blow out the crankcase breath. One thing to note is the oil is not thin and does not have a strong smell of gas either.

I have rebuilt the breather with a new spring and disc under the recoil starter of the mower with the assumption it was staying open allowing oil past it. This also did not fix it.

Other things I have done to try and remedy this is done a valve job. Both the intake and exhaust where about 0.002" out of spec but are within spec now. Still, none of these remedies have helped.

Next things would be to check if the clearance between the cylinder wall and piston rings is within spec, but I have not had a chance to tear it down that far yet.

Details of the engine are : Spec No PH-XT675-2011 serial number 4210428758

Does anyone have any ideas or known fixes for this issue?

Thanks in advance to everyone who tries to help!!!!

Your head gasket is leaking between the cylinder and the push rod tube.
This is often a by-product of a leaking carburettor because if you try & crank it with liquid fuel in the cylinder, the liquid can not compress so it blows out the gasket.

bertsmobile1 said:

Your head gasket is leaking between the cylinder and the push rod tube.
This is often a by-product of a leaking carburettor because if you try & crank it with liquid fuel in the cylinder, the liquid can not compress so it blows out the gasket.

Click to expand...

Thanks Bertsmobile1 for the response. I do not have the time to do a more comprehensives tear down to replace the head gasket on this mower currently. Is it possible to just block the tube leading into the air filter housing from the crankcase breather for now? Will the back pressure caused by clamping that hose cause issues with the engine? Was this a common problem on these mowers? Are there other signs that the carb was leaking liquid fuel into the intake besides the symptoms I have been describing? The reason I ask is I have been checking the spark plug and there are no signs that the mower has been running rich.

Thanks!

No that will not work it will only get worse and blow the seal on the dip stick tube and then the fuel pump if it has one.

If you need to use the mower disconnect the breather tube.
Block off the hole in the filter housing then run some more hose on the breather to a catch bottle which will slowly fill up with oil.

Check the oil, if it smells like fuel then the oil must be changed .
Failure to do this will destroy the engine very quickly.

It is all of 2 to 3 hour job if you have never done one before.
Whip the blower housing off ( 4 bolts )
Undo the tip handle and stand the mower on its back so the cylinder is pointing up.
On some mowers you need a weight on the handles to stop them falling over.
Undo the two bolts holding the carb manifold to the head, leave the carb attached to it and move it out of the way.
Leave the muffler in place undo the 8 or 9 bolts holding the head in a criss cross pattern

Assembly is the reverse.
Dont have to do it in one hit.
1/2 hour after dinner over 3 or 4 nights.

I had a chance to pull the head on the mower. Please take a look at the pictures. The head gasket seems to be in great condition with no visible damage other than slight separation when removing it. Could the rings really be bad on a three year old engine only used for 4 months out of the year?

bertsmobile1 said:

No that will not work it will only get worse and blow the seal on the dip stick tube and then the fuel pump if it has one.

If you need to use the mower disconnect the breather tube.
Block off the hole in the filter housing then run some more hose on the breather to a catch bottle which will slowly fill up with oil.

Check the oil, if it smells like fuel then the oil must be changed .
Failure to do this will destroy the engine very quickly.

It is all of 2 to 3 hour job if you have never done one before.
Whip the blower housing off ( 4 bolts )
Undo the tip handle and stand the mower on its back so the cylinder is pointing up.
On some mowers you need a weight on the handles to stop them falling over.
Undo the two bolts holding the carb manifold to the head, leave the carb attached to it and move it out of the way.
Leave the muffler in place undo the 8 or 9 bolts holding the head in a criss cross pattern

Assembly is the reverse.
Dont have to do it in one hit.
1/2 hour after dinner over 3 or 4 nights.

Click to expand...

Hey Bertsmobile1, Any chance you have additional ideas on what could be causing this oil problem?

Thanks!

Well those shots do not show what I was expecting to see.
Just how smokey was that engine when running ?
That is a really badly coked up piston & head.
If it was in my shop the next step would be taking the scotch brite to the piston & head looking for cracks.
I can not see any obvious leakage points,
Also run a steel rule across the head and barrel to check for flatness

Is the exhaust valve sealing. It just looks like it isn't setting flush on the valve seat in the head.

bertsmobile1 said:

Well those shots do not show what I was expecting to see.
Just how smokey was that engine when running ?
That is a really badly coked up piston & head.
If it was in my shop the next step would be taking the scotch brite to the piston & head looking for cracks.
I can not see any obvious leakage points,
Also run a steel rule across the head and barrel to check for flatness

Click to expand...

I will go tear back into it now. But this mower never burned oil or smoked except when the oil from the crankcase mades it way through the air filter compartment back into the carb. Sometimes you could see white exhaust, but that was always eventually followed by the carb getting fuel of oil and the motor choking itself. I will clean both the head and piston tonight and see what I find.

ILENGINE said:

Is the exhaust valve sealing. It just looks like it isn't setting flush on the valve seat in the head.

Click to expand...

Hey IlEngine, Thanks for the reply. I will take a look at the seal but when I looked it seemed flush. I will see if I can't get any feeler gauges to judge the gap if any.

Okay, I went back in and cleaned off the head and the piston to the best of my abilities at the time. The piston cleaned up pretty well and I could not find any cracks. I also cleaned the head and again couldn't find anything out of the normal. I also looked over the cylinder wall and it looks in great condition. You can still see the lines from the initial factory honing on the cylinder wall. I have taken apart many briggs with worse condition cylinder walls that are still in great running condition. I also took a look at the breather valve cover on the crankcase and it looks pretty good. I have attached more pictures of each of the above mentioned points.

Tomorrow I am going to go rent a compression tester from the local auto parts store. Does anyone know what value I should be getting on this mower? If the compression checks out, any ideas?

Thanks everyone!

Save your money.
A compression test will tell you absolutely nothing on these engines because of the decompression and if you defeat the decompression you will not be able to rotate the engine.
Normally I would have suspected the oil ring but generally when they are gone the engine smokes really badly.
At this point in time my tendency would be to pull the piston out & check the rings.
Also to check the bore for cracks.
In order to get oil blowing a few feet out of the breather you need a lot of crankcase pressure.

bertsmobile1 said:

Save your money.
A compression test will tell you absolutely nothing on these engines because of the decompression and if you defeat the decompression you will not be able to rotate the engine.
Normally I would have suspected the oil ring but generally when they are gone the engine smokes really badly.
At this point in time my tendency would be to pull the piston out & check the rings.
Also to check the bore for cracks.
In order to get oil blowing a few feet out of the breather you need a lot of crankcase pressure.

Click to expand...

Where is the automatic compression release even located on one of these engines. I thought they tended to only put those on larger (10hp+), guess not. Any thoughts on how I could jury-rig something to make a leak down tester? I would prefer not to have to buy any diagnostic tools. How difficult is splitting the case to remove the piston for checking the rings etc. I checked the bore pretty well from what is visible when the piston is down and couldn't find anything wrong with it.

Thanks,

Check out U-tube dozens of "how to make a cheap leak down tester " videos out there.
You can pump up the cylinder with a reasonably good tyre foot pump.

bertsmobile1 said:

Check out U-tube dozens of "how to make a cheap leak down tester " videos out there.
You can pump up the cylinder with a reasonably good tyre foot pump.

Click to expand...

Okay. I built a leak down tester. How long should it hold 100 psi? When I take the reading from the second gauge do I wait some amount of time to take it?

bertsmobile1 said:

Check out U-tube dozens of "how to make a cheap leak down tester " videos out there.
You can pump up the cylinder with a reasonably good tyre foot pump.

Click to expand...

Okay. So I built a leak down tester and used it. I had the regulator at 100psi and was reading about ~94 psi on the second gauge. From what I can tell these are good results? Can anyone confirm? If they are good, any other ideas on what to test besides tearing the whole thing down and checking all specs?

I know this is an old post, but I’m at the same spot with my mower
I replaced the head gasket and cleaned the CC vent spring and cap and opened the oil drain hole
I’m still having oil overflow
I guess pulling the piston and replacing the rings is next,
just wondering if the OP ever solved his problem or identified the cause
thanks

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