Kohler Command 12.5CH

[Cas8101]

New here so bare with me. Working on a welder generator that is powered by a Kohler 12.5 command. Been sitting for years, got it to run on carb cleaner and die. Pulled carb to clean and went to inspecting a few other things. It was backfiring, pulled valve cover and rocker arms and push rods were fine. I also noticed an exhaust leak so while inspecting this I pulled muffler and found that where the muffler bolts to the head that around one of the bolt holes quiet a bit of metal was missing.

Could this be from Years of leaking exhaust gases?
Exhaust valve issues?
Possible blown head gasket?

I bought some extreme temp epoxy putty to possibly make a repair rather than replace the head

 

[jhellwig]

Helicoil. That would be a very easy one to do. Kits aren't that expensive on Amazon.

On second look it looks like it has been helicoiled already but now I see what you are talking about. You could jb weld it but I would just leave it alone.

 

[Cas8101]

Helicoil. That would be a very easy one to do. Kits aren't that expensive on Amazon.

On second look it looks like it has been helicoiled already but now I see what you are talking about. You could jb weld it but I would just leave it alone.

With how the exhaust manifold gasket goes in between it and the muffler do you see sealing issues with leaving as is? I may try the putty for chits and giggles. Really my objective is to get this running and test its power output. If it’s generating power from receptacles and has good weld output I may dive deeper into its other issues. Quite a bit of oil on one side of motor. Thinking maybe blown head gasket. Has like 700 hours on it, a 1995 Miller Bluestar 180k

 

[repairman54]

Since that ''ear'' is open behind it, not a blind hole, I would nut and bolt it to get it running for testing if threads are bad rather than helicoil it. As long as it seals around the port opening I'd say good to go.

 

[Cas8101]

Waiting on a new exhaust manifold gasket and a couple orings for the carburetor. I had popped the cover on the valves to inspect rockers and push rods so today I cleaned up the mating surfaces and sealed with the right stuff grey. I’ve had better luck on valve covers with grey over the black I’ve used before. Fingers crossed m, should have her back up and running by Thursday

 

[Cas8101]

Got it semi put back together last night to attempt to run it and check power output from welding leads/receptacles. It still runs the same, which is starting to briefly then backfire out the intake and possibly the exhaust as well. I’ve pulled valve cover and checked rockers and push rods prior to this so pretty sure valves are not the issue. Believe it’s ignition or out of time. Gonna check spark plug and coil but I’m pretty sure I’m gonna find out I have a sheared flywheel key if I pop the flywheel off. Will report back with my findings

 

[Cas8101]

Ok so to confirm valves are not the issue I did a leak down test today. Only 10 percent leak down so good there. Have good compression, valves are indeed working, have spark, have a working carb. Still runs and dies and backfires. So I have not pulled flywheel to check key but don’t think it’s sheared when rotating flywheel by hand the magnet is just clearing the ignition coil on TDC so that seems to check out in my book as in time.
Think I’m going to slap a new coil in it and see if that’s the issue. I put a new plug in it already even though plug was fine that was in it.

Appreciate any thoughts or expertise fellas

 

[Lawnman23]

What's the full model number on the engine? It will be CH12.5-xxxx or similar.

Kohler has had a few different ignition advance systems in the past (ASAM, DSAM, DSAI, MDI) that have different mechanisms for spark control. The first three have a dedicated controller mounted on or under the blower shroud. The MDI type does not but has a specific flywheel required. Kohler released a kit for converting the older systems to MDI due to issues they were haveing with them.

Not sure thats the issue with yours yet, but need the full model number to lookup which setup it has.

 

[Cas8101]

Well when tinkering I took a look at the coil and saw its kill wire plugged into the top. Decided to unplug that and see if there was any change. Boom she fired up and was running with no misses. Choked engine to kill it.

Plugged kill wire back into coil and Chased kill wire from ignition coil back to switch on side of welder and where it plugged into the switch there was another wire there. Chased that wire and found it provided power to the oil pressure switch. Unplugged it from that oil pressure switch to retest and wouldn’t you know it engine fires up and running like a top. Bad oil pressure sensor!!!

Tested all receptacle’s and they were providing 120 volts. Hooked up a light and a grinder and they ran fine. Decided to hook my welding leads up to it and burnt a rod of 6011 without issue. We are back in business baby. Need to button everything back up and give her a cleaning. She has also earned an oil change!

Minor issues still need to address. Believe she is running maybe a 100 RPM to slow. She was showing 58.5hz and tried to make adjustment on carb with no increase. Maybe need to look at the governor setup and see what I can do there. Says on the cover should do 60hz at 3750 rpm. I would think from other generators I’ve checked that it should be around 61.5hz

 

[The_Eric]

Glad you got it sorted, but a slight correction - the wire you're referring to doesn't provide power to the oil switch, instead during low oil level (or possibly pressure) conditions, the switch grounds the coil and shuts the engine off.

 

[Cas8101]

Glad you got it sorted, but a slight correction - the wire you're referring to doesn't provide power to the oil switch, instead during low oil level (or possibly pressure) conditions, the switch grounds the coil and shuts the engine off.

Thanks for the clarification on that. Right or wrong I just assume to leave that switch disconnected. I check oil level on all equipment religiously, and I’m not sure what aftermarket options will work for me and Miller has discontinued many things for this welder the oil pressure switch is one of them. It’s a 3 wire 4psi switch but I’m not sure if it normally open or normally closed. Electrical stuff isn’t my strong suit