z125skh-54 (zt740-3013)

zah5025

Forum Newbie
Joined
May 2, 2020
Threads
2
Messages
6
Hello,

My zero turn recently sounded a bit louder, started backfiring and losing power while under load (accelerating or engaging the blades).

I replaced air filter/pre-cleaner, fuel filter (using fresh gas before all this happened), oil, oil filter, and spark plugs. I cleaned the carburetor and replaced the gaskets. I checked the fuel lines, ignition module gap, spark plug gap, valve clearances, and muffler. All seem ok.

At this point, it doesn't backfire anymore, but it still bogs down under load (accelerating or engaging blades). I haven't tried to cut anything, but I am sure it would lose significant power when cutting heavy grass.

Wondering if the carb and carb linkages need adjusting. I put it back together the same way it was originally, but maybe I need to make some adjustments? Is there a diagram or something out there that can help with this?

Or maybe it is something else... I'd take it to a shop, but money is very tight right now.

Any help would be really appreciated. Thank you.
 

bertsmobile1

Lawn Royalty
Joined
Nov 29, 2014
Threads
64
Messages
24,647
It would help if we knew what engine we are diagnosing
I would put my money on a leaking head gasket between the push rod tunnel & the cylinder
The quick & dirty check is to run the engine for 10 minutes or more, turn it off, count to 10 then pull the dip stick
If smoke wafts out of the tube then the head gasket is gone
Another confirmation is checking the breather
Blowing on the up stroke indicates a blown head gasket .
A knock or rattle when the engine is suddenly loaded ( blades turned on or cutting very thick heavy grass ) or turned off .
 

zah5025

Forum Newbie
Joined
May 2, 2020
Threads
2
Messages
6
It would help if we knew what engine we are diagnosing
I would put my money on a leaking head gasket between the push rod tunnel & the cylinder
The quick & dirty check is to run the engine for 10 minutes or more, turn it off, count to 10 then pull the dip stick
If smoke wafts out of the tube then the head gasket is gone
Another confirmation is checking the breather
Blowing on the up stroke indicates a blown head gasket .
A knock or rattle when the engine is suddenly loaded ( blades turned on or cutting very thick heavy grass ) or turned off .
It is a zt740 kohler 25hp.

While working on it last night, I found that it is only running on one cylinder. I checked by disconnecting one ignition module and starting it up. it ran with only the left ignition module connected, but it did not run with only the right ignition module connected. I swapped spark plugs, no change. I swapped ignition modules, no change. Does that mean it is only getting fuel to the left cylinder and not the right cylinder?
 

bertsmobile1

Lawn Royalty
Joined
Nov 29, 2014
Threads
64
Messages
24,647
pull the rocker covers off and check to see if you have lost a pushrod
 

zah5025

Forum Newbie
Joined
May 2, 2020
Threads
2
Messages
6
Push rods are all there. Everything there appears to be functioning properly.
I noticed some weird airflow below the cylinder that wasn't firing. I pulled the head and found that the gasket was blown. Will update once I have a new gasket installed.
 
Top