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gzx3sc

Kohler M14 Magnum Valve issues

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gzx3sc

I'm about to pull what's left of my hair out. I have a 1995 314 Hydro with the M14 Magnum engine with only 400 hours. It's always had a cough / miss about every 60 seconds that gradually got worse. It then stared making a fluttering noise out the exhaust and was losing power.

I first disabled the Automatic compression release and thought the fluttering problem was solved. I put an older K series carburetor on it and that solved the cough / miss issue and it ran great for two hours of heavy mowing.

The next mowing 4 days later, it started fine but as soon as I engaged the blades it started fluttering out the exhaust again. :thumbs:

What I've done:

Check valve clearances (right on spec.)

I've lapped the valves and seats. (They look great)

I've checked to make sure the ACR is still dis-engaged

Valve guides are fine with correct amounts of clearance

The valves slide up and down the guides like butter

Guys I'm at a total lose. I've never been this stumped. It's like the exhaust valve is sticking but I have no idea what's making it stick up slightly!!! :D

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TT

This might be a long shot, but it won't cost anything to try it......

Disconnect the kill wire from the ignition module (coil) and try it.

You might want to check the flywheel key too.

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gzx3sc

I had the valves and seat ground today. Still no luck. I've never been stumped like this before. :thumbs: Vavle clearances are to spec. I don't get it.

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gzx3sc

Well mystery solved. I think what happened was the muffler started plugging over time which overheated the exhaust valve and caused the seat to go out of round. After grinding the valves and seats (Machine shop) it was still acting up. I removed the muffler (which I had done earlier) but before grinding the valves and it cleared up fine. Eventually the muffler had enough back pressure to cause the valves not to shut completely? I priced a new muffler and it was $125 :thumbs: so I'll be installing the old salt and pepper for $7.95. :D

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Pettybilt

I know that if you use the wrong weight oil in some kolhers the lifters will pump up and act like a solid lifter not allowing the valves to close. My step father just had this problem on a 23 hp k. We had to take the lifters out, take them apart and clean them out with carb cleaner. I use to work at a small engine shop, and a guy brought in a mower acting like what you are talking about, sure enough he had put the wrong oil in it. Sounds crazy, but i called Kolher tech, and they told me to change the oil and clean the lifters out. Maybe something to look at if it starts acting up again.

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gzx3sc

The single cylinder K series and Magnums have solid steel tappets so I'm not sure how that could happen, but if I get a twin some time I'll keep that in mind.

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Pirate

I occasionally get the same, fluttering and loss of power from my 14M.

I notice, when I tap on the muffler, there is something (baffle?) rattling inside.

Possiblly, at times it blocks the flow?

Has anyone had the problem, and fixed it with a new muffler?

I think I might cut it open, from the back side, and see if I can remove the loose part, or weld it back in place. hopefully it didn't hurt the exh. valve or seat.

Or maybe it's time for a custom exhaust!

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buckrancher

I occasionally get the same, fluttering and loss of power from my 14M.

I notice, when I tap on the muffler, there is something (baffle?) rattling inside.

Possiblly, at times it blocks the flow?

Has anyone had the problem, and fixed it with a new muffler?

I think I might cut it open, from the back side, and see if I can remove the loose part, or weld it back in place. hopefully it didn't hurt the exh. valve or seat.

Or maybe it's time for a custom exhaust!

YES YES and YES

I wish I had seen this from the first post I could have told you guy's it's

the baffle in the muffer blocking the exit hole

had the same trouble with the 314H I got off a dealer cheap because they

did'nt know what was wrong with it. got It home and found the baffle was

broke inside and moving around and would cover the exit hole occasionally

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Save Old Iron

got It home and found the baffle was

broke inside and moving around and would cover the exit hole occasionally

I had the same scenario happen with an inboard stern drive Mercruiser engine in a boat. The boat would cruise all day long at normal temp if the engine was kept below 3000 RPM.

If the throttle was cracked open to above 3500 RPM, the temp gauge would spike to the overheat indication within 30 seconds. :thumbs:

Turns out that large chunks of broken scale was present in the water jacket for the exhaust manifold. The scale was heavy enough not to be churned up into the outlet holes of the manifold below 3500 RPM . Higher RPM's churned up the flakes and plugged the water jacket outlets to the outdrive when RPMS went higher than 3500?

This sounds very similar.

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