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kholer no fire

#1

S

smallenginerepairs

I have a cub cadet zero turn mower with a kholer kt735 spec 3013 motor which, I've just changed the head gasket on. the cylinder now has 150 lbs of compression. the other cylinder has 125lbs of compression. I've set the valve clearance at 5 thousands at top dead center. the 125lb cylinder plug is carbon edge up after running, the 150lb side is not firing at all. I have new coils on both sides and checked spark and both cylinder are firing strong. why won't the one cylinder fire? Any ideas would help.


#2

Tiger Small Engine

Tiger Small Engine

smallenginerepairs said:
I have a cub cadet zero turn mower with a kholer kt735 spec 3013 motor which, I've just changed the head gasket on. the cylinder now has 150 lbs of compression. the other cylinder has 125lbs of compression. I've set the valve clearance at 5 thousands at top dead center. the 125lb cylinder plug is carbon edge up after running, the 150lb side is not firing at all. I have new coils on both sides and checked spark and both cylinder are firing strong. why won't the one cylinder fire? Any ideas would help.
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Have you checked exhaust with an infrared thermometer or sprayed water on exhaust with engine running? Compression from one cylinder to other cylinder is a 17% difference, which is a bit higher than the ideal 10% differential, but not alarming. If you have good strong spark and compression, the carburetor is the next thing to be checked. What type of carburetor is it specifically (ie: Walbro LMK, etc.)?


#3

S

smallenginerepairs

Tiger Small Engine said:
Have you checked exhaust with an infrared thermometer or sprayed water on exhaust with engine running? Compression from one cylinder to other cylinder is a 17% difference, which is a bit higher than the ideal 10% differential, but not alarming. If you have good strong spark and compression, the carburetor is the next thing to be checked. What type of carburetor is it specifically (ie: Walbro LMK, etc.)?
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there can be no fire in that cylinder if the plug is wet with gas and the pipe is cold. I put an oem walbro carb on. it. the problems started with a fire. the customer had an oil. leak, and one day when he was finished mowing he shut it off .soon after a fire started at the back of the motor. he put the fire out, but it melted the plastic choke lever on the carb to where the linkage fell off. when I got it I bought two different aftermarket carbs for it but neither would work. I bought an oem walbro carb put it on and the motor was surging. I set the valve clearance on both cylinders and it still surged. when I took the plugs out the left bank has a wet plug l. I checked compression and the left bank had 95lbs and the right had 125lbs of compression . the left bank had a bad head gasket. I took it apart and the bottom of the gasket was. blown. I cleaned everything ,visually checked the head no play in the valves and everything looked good.i put it back together and now that cylinder has 150 lbs of compression. I am buying a voltage rectifier a friend said might be the culprit, but I thought the rectifier only changed stator output from ac to DC voltage and monitored the charging of the battery. My friend said it also has to do with timing of spark plug firing ??? I am at a loss and don't know where to go from here. I would appreciate any help you can give.


#4

StarTech

StarTech

Have you tried one of two things. Swapping the plugs or installing new known good plugs? They do fail where you have out of the engine but under the compression load. I even had this that was causing on a Briggs single cylinder engine.

And the voltage regulator/rectifier has nothing to do with the CDI ignition system as it a magneto ignition and requires no input voltage from the charging system.


#5

S

smallenginerepairs

StarTech said:
Have you tried one of two things. Swapping the plugs or installing new known good plugs? They do fail where you have out of the engine but under the compression load. I even had this that was causing on a Briggs single cylinder engine.

And the voltage regulator/rectifier has nothing to do with the CDI ignition system as it a magneto ignition and requires no input voltage from the charging system.
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I've put new plugs in twice. when I took the head it was slightly warped but I used emery cloth to sand the high points then used a straight edge to check it an it was fine. if that was a problem I wouldn't have 150lbs of pressure. I wonder if this could be a cam issue?


#6

S

smallenginerepairs

smallenginerepairs said:
I've put new plugs in twice. when I took the head it was slightly warped but I used emery cloth to sand the high points then used a straight edge to check it an it was fine. if that was a problem I wouldn't have 150lbs of pressure. I wonder if this could be a cam issue? when I set the valves i turned the engine over and both lifters acted fine. I am confused, I have excellent spark, good compression and fuel, it should fire
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#7

StarTech

StarTech

Swap out the coils and test, you could have defective new coil. Testing is the only way to check, if the running changes sides then you have bad coil.


#8

S

smallenginerepairs

StarTech said:
Swap out the coils and test, you could have defective new coil. Testing is the only way to check, if the running changes sides then you have bad coil.
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I've already swapped coils new spark plugs twice i even took kill wires off coils, it still won't fire. I'm at a loss for anything now .I have to get this mower fixed. I don't give up, but I've exhausted all my known options. I am at a loss but cannot give up.


#9

Tiger Small Engine

Tiger Small Engine

smallenginerepairs said:
I've already swapped coils new spark plugs twice i even took kill wires off coils, it still won't fire. I'm at a loss for anything now .I have to get this mower fixed. I don't give up, but I've exhausted all my known options. I am at a loss but cannot give up.
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New OEM carburetor is hunting and surging, so that means you are running lean and need more fuel, or less air. Check for intake air leak around gaskets. Was old OEM Walbro carburetor hunting and surging? Have you tried checking temperature of exhaust? Have you sprayed water on exhaust pipes?


#10

S

smallenginerepairs

Tiger Small Engine said:
Have you checked exhaust with an infrared thermometer or sprayed water on exhaust with engine running? Compression from one cylinder to other cylinder is a 17% difference, which is a bit higher than the ideal 10% differential, but not alarming. If you have good strong spark and compression, the carburetor is the next thing to be checked. What type of carburetor is it specifically (ie: Walbro LMK, etc.)?
Click to expand...
i checked the exhaust with water, it's cold and spark plug wet. I bought an oem walbro carb. I tried 2 different aftermarket carbs and it surged so I bought an oem walbro carb, the exact same one as the original and it still surges. 2 new aftermarket coils. right side fires the left doesn't. I swapped coils from one side to the other, right side fires left side does not. I pulled kill wires off both coils to eliminate a blown diode in the wiring still the same surging and no fire on the left side.


#11

H

hlw49

Has fire getting fuel on one cyllinder next thing could it be a bad intake manifold? Bad air leak. Or are the vlaves working?


#12

S

smallenginerepairs

hlw49 said:
Has fire getting fuel on one cyllinder next thing could it be a bad intake manifold? Bad air leak. Or are the vlaves working?
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I've sprayed carb cleaner all around intake manifold while running and no changes in ram. valves are working and are set at .005 at top dead center. can a warped head cause this problem? I checked it when I replaced the head gasket with a straight edge and it looked good, and I now have 150 lbs of compression.


#13

woodstover

woodstover

smallenginerepairs said:
I've sprayed carb cleaner all around intake manifold while running and no changes in ram. valves are working and are set at .005 at top dead center. can a warped head cause this problem? I checked it when I replaced the head gasket with a straight edge and it looked good, and I now have 150 lbs of compression.
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Valves adjusted at TDC on the compression stroke?


#14

dicksonm

dicksonm

It sounds like you're dealing with a tricky issue on your Cub Cadet mower. Since both cylinders have spark and you've set the valve clearance correctly, there are a few things to check. First, inspect the carburetor and fuel delivery to the cylinder with 125 lbs of compression; it may not be getting enough fuel. A clogged jet or fuel line could be the culprit. Additionally, check for any air leaks in the intake manifold or gaskets that could affect the air-fuel mixture. If everything looks good there, consider testing the compression again to ensure it hasn’t changed, and double-check the timing as well.


#15

A

Auto Doc's

I undo the valve rockers on the dead cylinder and apply shop air pressure to the cylinder. There will be some air escaping out of the crankcase, but not past the intake or exhaust valve. This engine should run even with the difference in compression on that side, but I have had a leaky valve trick me before on these,

Has the flywheel key been checked to make sure it is not partially sheared?


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