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I own a 2005 exmark lazer z 60. I bought this mower brand new and I am the only operator. The mower just turned twelve-hundred hours. So here is the problem. When I engage the collection system the mower really boggs down and the rpms drop to a point of almost stalling but work their way up to about thirty-five hundred rpm. Whenever a go up any incline the mower will loose rpm and stall if I don't turn away and get to a more level plain. This has been going on all this season. Up until this season it has run fine. I have re-built the ultra vac, checked all pulleys they spin freely. The engine has a new short block, carburetor, new heads, new clutch. The hydraulics checked out and are within factory specs. No one can seem to figure out what is causing this problem. I had it checked out at the certification school for kohler engines. They suggested to take to my exmark dealer. They won't be able to look at it until March because they have not seen the machine since I bought it. My local mechanic and the kohler people have never run into this before. Thet are stumped. Any help would be appreciated.

Sounds very much like a governor problem in particular a frozen governor not allowing the throttle to open up when a load is applied to the motor.
Get some one to sit in the seat and turn the blades & vac on and off.
you should see the thrttle opening up wide as the engine bogs down.

bertsmobile1 said:

Sounds very much like a governor problem in particular a frozen governor not allowing the throttle to open up when a load is applied to the motor.
Get some one to sit in the seat and turn the blades & vac on and off.
you should see the thrttle opening up wide as the engine bogs down.

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Yes it does.

I don't know how to explain this but just listen to the engine while its running. Does it sound like it is running on one cylinder. Your issues sounds like a power loss which could be an engine on one cylinder. You may be able to listen to another twin cylinder engine that is running correctly and then compare it to yours. Doesn't matter what brand, most of the engines sound the same on one cylinder

Lack of a better description, an engine on one cylinder sounds throaty.

I agree sounds like it's only running on one cylinder.
Take the plug wire off one spark plug. If engine does not start then you have no fire on the one that is still plugged up.

ILENGINE said:

I don't know how to explain this but just listen to the engine while its running. Does it sound like it is running on one cylinder. Your issues sounds like a power loss which could be an engine on one cylinder. You may be able to listen to another twin cylinder engine that is running correctly and then compare it to yours. Doesn't matter what brand, most of the engines sound the same on one cylinder

Lack of a better description, an engine on one cylinder sounds throaty.

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The engine is brand new. Leak down test and vacuum test have been done and there are no issues with the engine.

I find that the eases way to know if it is running on one cylinder or two is the heat of the exhaust pipe. I agree with bertsmobile is the governor working or is the engine losing power which could be a number of things. As I recall a new short block comes as a striped down block.

reynoldston said:

I find that the eases way to know if it is running on one cylinder or two is the heat of the exhaust pipe. I agree with bertsmobile is the governor working or is the engine losing power which could be a number of things. As I recall a new short block comes as a striped down block.

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So here is what happens. With the mower going at full ground speed(about 10 mph) as soon as I engage the pto the mower slows down so fast I almost fall forward off the machine. As the rpms pick up the ground speed at best is about 6 mph. If I go up any incline it slows almost to a full stop. If I disengage the pto there does't seem to be any problem as far as a normal operation. If I take off the collection system the mower will operate normal.It has seem to stump anyone who has looked at it.

shelley said:

So here is what happens. With the mower going at full ground speed(about 10 mph) as soon as I engage the pto the mower slows down so fast I almost fall forward off the machine. As the rpms pick up the ground speed at best is about 6 mph. If I go up any incline it slows almost to a full stop. If I disengage the pto there does't seem to be any problem as far as a normal operation. If I take off the collection system the mower will operate normal.It has seem to stump anyone who has looked at it.

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If this is stumping experience mechanics that are working on it sure has me stumped when I can't even see or hear the machine.

reynoldston said:

If this is stumping experience mechanics that are working on it sure has me stumped when I can't even see or hear the machine.

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I posted this hoping some one may have experienced a similer problem.

Nothing to be stumped about.
Without the blades engaged or fan blowing there is effectively no load on the mower so it chufFs along happily.
When you put a load on the engine, the engine slows down so the govenor should allow the throttle to open further.
Yours is obviously not doing this and you were told to check this a while back but obviously have not bothered to do so or if you did you did not bother to tell us .
You were also advised to check the pipes for even amounts of heat signifing the engine was running on both cylinders, again with no response from you.
If this is the level of communications you have with the "experts" no wonder they are stumped.

bertsmobile1 said:

Nothing to be stumped about.
Without the blades engaged or fan blowing there is effectively no load on the mower so it chufFs along happily.
When you put a load on the engine, the engine slows down so the govenor should allow the throttle to open further.
Yours is obviously not doing this and you were told to check this a while back but obviously have not bothered to do so or if you did you did not bother to tell us .
You were also advised to check the pipes for even amounts of heat signifing the engine was running on both cylinders, again with no response from you.
If this is the level of communications you have with the "experts" no wonder they are stumped.

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My response in post #3 answers the governor question, however, I thought my answer in post #6 would address the cylinder issue but YES there is even amounts of heat from the pipes.

shelley said:

The engine is brand new. Leak down test and vacuum test have been done and there are no issues with the engine.

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# 6 post
Leak down test, tells you good compression, vacuum test, vacuum leak poor low speed. Then how was these test done?? It takes more then this to fire a cylinder. You still have fuel, spark, and timing. New engine, working for a dealer I find that doesn't mean a thing. You are hoping someone has the same problem. OK what problem. The only thing I see here is the engine has no power which could be many reasons. Fuel, spark, compression, timing, you are missing one of these things or it would run right. No issues with the engine? OK if the engine isn't the problem is something getting seized like a bearing. I guess look for hot spots?

shelley said:

My response in post #3 answers the governor question, however, I thought my answer in post #6 would address the cylinder issue but YES there is even amounts of heat from the pipes.

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Yes, we manually opened the throttle , bypassing the governor and it worked properly / made no difference is a response
Wih the PTP running I pushed the govenor arm and it returned properly is a response
Yes is not a response.