Kohler twin cylinder red glowing exhaust

[tkos115]

I have a Kohler CH22S twin cylinder engine on a Toro lawn tractor. It had a bad ignition coil on the left cylinder from mice chewing the wires. I replaced the coil and now it runs fine. I also power washed the engine block because it was COVERED in grease and other debris. I noticed that when I have the engine running at half throttle or more the pipe between the head and muffler body will start to glow red. Using the choke doesn't seem to help reduce the over heated pipe. I don't recall seeing it do this before power washing it. I'm guessing maybe there was so much grease around the intake manifold flange it was sealing a small leak and now it's more prevalent. It only has one carburetor for both heads so I'm assuming it's an intake leak at that head? The valves aren't adjustable and both heads have new plugs. It will run on each cylinder alone but it runs worse if I run it on the head that seems to run lean. It also won't rev as high.

At idle it runs great and starts great but that head pipe turns red after about 15 sec at higher speeds.

 

[sgkent]

dark red to cherry red is about 1100F to 1200F. I'd be looking for a timing issue or a vacuum leak on that side. When it cools run a leak down to be sure that the exhaust valve isn't stuck partially open where the exhaust is always flowing out it during the cycles. With a common carb it is hard to imagine a general mixture issue. Does the coil have elongated holes where the timing can vary?

 

[tkos115]

The coil has slotted holes but only for up and down movement. I set the gap between the coil and flywheel to spec.

 

[sgkent]

The coil can only go one way, meaning if you flip it over it won't fit - the placement of the pickup doesn't change? I am guessing it only goes one way but if the coil pickup was offset, and the coil was flipped over that would change the timing. Otherwise do a leak down and make sure the exhaust valve is sealing properly and not leaking exhaust both during the power stroke and exhaust stroke. Or look for a vacuum leak on that cylinder. Maybe someone else with better ideas will be along or someone who has seen and solved it before. Good luck.

 

[VegetiveSteam]

What's the part number of the coil you used as the replacement? Did the small wire connection or connections look different from the coil you took off?

 

[tkos115]

24 584 36-S is the number I used. I put it back in facing the way I took it out including the wires. Both pins looked the same. I personally don't remember seeing the pipe glow until after I pressure washed the engine around the head and intake manifold.

 

[sgkent]

If it was hot when you washed it, it could have cracked something. That said, it sounds like a lean mixture problem or a sticky exhaust valve. The only other thing I can think is that the other cylinder is not firing properly now after washing it, and the cylinder that is glowing is carrying all the load.

 

[tkos115]

I idled it for a few min then let it sit for about 5min before washing it. If I pull the plug wire on the other side so it only runs on the side thats running hot, it's more noticeable in how much the engine drops off as compared to me pulling the plug off the hot cylinder. When I try to run it at high speed only on the hot cylinder it sounds like it struggles more and doesn't seem to reach as high of a speed compared to if I did the same thing on the other cylinder.

 

[tkos115]

It also seems to pop through the intake a bit now too when throttling up quick

 

[VegetiveSteam]

24 584 36-S is the number I used. I put it back in facing the way I took it out including the wires. Both pins looked the same. I personally don't remember seeing the pipe glow until after I pressure washed the engine around the head and intake manifold.

That is the correct part number. How does it run if you run it on just one cylinder at a time?