M18 Engine

[Deerlane]

When I got this engine, it was running poor on #1 cyl. #2 cyl doing all the work, but #1 will run by itself but poor. Spark plug gets black dry soot.
1. Install new plugs and Check compression on both cyl, they are the same.
2. Leak down test on both cyl, less then 5% leak.
3. Removed intake and carb, check gaskets and for water, dirt in carb., none. Intake gaskets good. No cracks in intake
4. Check key on flywheel and install new module, no change.
5. Removed #1 cyl, check all valves and guides. Lap both valves and check clearances. Intake set at .005 and Exh at .013, in spec for year of engine. Check cam/valve lift.
6. Install all cyl parts and new gaskets, and it's the same
I'm lost. This engine has done this when I install it NEW back in 2000.
Help from some one. I am a 35 year small engine mechanic and I lost!
I must need that 36 year. LOL

 

[gainestruk]

Have you changed plug wire ?

 

[ILENGINE]

Something for you to try. remove the spark plug from the bad cylinder, ground the spark plug wire. Install a compression gauge in that cylinder and then start the engine on the other cylinder. Check the compression reading on the gauge, which would be cranking compression. Now while running release the compression and allow in to pump back up. And recheck the compression. This would be running compression. I have seen cases such as your where you would get 90 psi while cranking, but would only produce 30 psi running.

 

[mechanic mark]

http://www.kohlerengines.com/onlinecatalog/pdf/tp_2204_b.pdf service manual for your engine, section 4 troubleshoot.

Have you check for restrictions in exhaust system on #1?

 

[Deerlane]

Thanks for the replies
gainestruk, The plugs wires and ignition mod is all in one.
ILENGINE, Thanks, I will try to see if there is a difference. I did this ones before with a B&S VanG. When they had soft cams.
mechanic mark, Thanks. I also have the hard copy from Garnder and Pitt Auto Schools in Ohio and Pa. No I did not check exh, I will. Pipe to muffler is 3" long, then in the can muffler. Both pipes share the same muffler.

I said one thing worng, this engine is a 2009 engine.

 

[Deerlane]

UPDATE>>>>ILENGINE, I tried your test on both cyl's. Crank compression is near 90 lbs on both 1 & 2. Run compression on both cyl's is around 55. Now this is with my gage at home. I will try with two other gages I have at work. Even though the are the same compression, I'm starting to think SPRINGS. At low off idle RPM's, no pop or miss. At 2400 rpm's I'm starting to getting the pop on #1.

 

[Mad Mackie]

Kohler Magnum twins are somewhat known for hanging up an exhaust valve, which may be happening as the engine temps and RPM rise.
A vacuum gauge connected into the intake system would show this, but not many small engines have an easy way to connect into the intake system.

 

[Deerlane]

Thanks Mad Mackie, There is no carbon on valve stem but I can replace the guide with new one I have, and install another old exh valve that I have here also. I will cut in and redo the face of the valve. I don't have new springs, will need to order. I may need heaver springs maybe?

 

[Deerlane]

Re: M18 Engine ( update )

Found the problem! wrong or bad/weak exh valve spring.