I have an older scag sthm 61" with a cv22 kohler command engine with about 1300 hours. . I have been fighting gremlins over the past years with it and getting by. The newest thing is that I was losing power and once I shut the pto off the engine reved right back up to speed. Now she is blowing blue smoke and eating oil like crazy. I took the plugs out and the left side was normal, but the right side was full of black crud and soot like stuff. I turned her over and e left side had good compression ( sucking my finger in and out) but the right side had notably less. I am assuming that there is excessive blow by on the right head and need a rebuild. Do they sell an engine rebuild kit? What am I looking at for cost? Is it worth the cost to have it overhauled?
#2
ILENGINE
Lets start by removing that right head, the one with low compression. Most likely the problem is either a blown head gasket, or sticking valve. Both are relatively minor repairs.
Ok. I did a compression test and the left side is around 100 and the right almost nothing. This is the plug with the crud on it from the right. I took off the valve cover and turned the engine over and both valves seem to be moving as they Should.
Ok. I did a compression test and the left side is around 100 and the right almost nothing. This is the plug with the crud on it from the right. I took off the valve cover and turned the engine over and both valves seem to be moving as they Should. View attachment 26478
Now that you have determined the spark plug looks good(joke)....and the valves are moving. You will have to take the head off as ilengine said to examine the head gasket.
Ok, pulled the head and one of the valve heads is broken, not sure if exhaust or intake. What's the best step from here? Total rebuild or just replace the bad parts? What else should I do or look for while I'm at this point Of disassembly?
Ok, pulled the head and one of the valve heads is broken, not sure if exhaust or intake. What's the best step from here? Total rebuild or just replace the bad parts? What else should I do or look for while I'm at this point Of disassembly? View attachment 26479
I would wire brush it and clean it up good to get a good look at every thing.
Disassemble just that head and valves and then go from there.
Check head for level...probably OK is the gasket appears to not been leaking.
Up date. I replaced the exhaust valve (lapped) and cleaned the head. I put the head back on (new head, intake, exhaust gaskets and head bolts) everything torqued to specs. Checked compression and I have 125 on each side. But now I can't get the mower to run. Turns over fine. Checked and there is spark. I tried putting some gas directly into the carb and the gas shot back out and actually stopped the engine from turning over momentarily and then it turned over. Is it a carb issue.? Not sure where to go from here. Really don't want to bring this to a repair place.
#9
ILENGINE
They problem could be something as simple as an overpumped lifter. Give it a few hours for the lifters to compress and see what happens.
I hope it's that simple. Would it matter what position the cylinder piston was in when I put it back together? Could I have screwed the timing up?
#11
ILENGINE
Changing the head gasket will not effect timing. but without pressure on the lifters, and the engine is turned over for some reason like going from TDC to BDC can push oil into the lifters and prevent the valves from closing.
Had a customer a few years ago that was using 30w in the single Command engine, and after running for a few minutes would stop running. Wait a few hours and would start back up. The Command normally calls for a multigrade oil and the straight grade was allowing the lifters to overfill and hold the valves open. I have seen where push rods would get bent from trying to turn the engine over without collapsing the lifters before trying to start.
I normally will remove the lifters and collapse them by wrapping in a clean rag, and inserting a small socket in the open end and putting the whole thing in a vise.
Tried starting it this afternoon and she would start to crank over and then stop and then start to crank and then stop. I will try to get a video of it tomorrow. So what ur saying is that I might have to take everything I just did, back part, remove the hydro lifters, bleed them and then put it back together?!:mur::mur::mur::mur::mur::mur::mur::mur::mur:
#13
ILENGINE
It sounds like a compression release problem. I would say at this point the lifters have bleed off and are no longer the problem, unless you bent the pushrods.
I have a leak down tester I'm going to use this afternoon. Whatever the out is, I know I'm going to have to remove the head again. What is the fix here? I don't understand how the timing got screwed up. Was it something I did when I put the head back on? The valves and lifters aren't adjustable and I didn't touch the inerds, so shat gives?
#20
ILENGINE
I don't think it has anything to do with the head that you worked on. Whatever is causing the problems is effecting both cylinders. Maybe the timing isn't off as much as something goofy with the firing of the plugs. Does this engine have the spark advance system. maybe something messed up with it.
Yes it has that "smart spark module" just seems weird that it ran (for lack of a better term) before repairing the valve and now this. Going to pull the flywheel to make sure the key didn't share and screwed the timing up. Everyone I talk to says it sounds like a timing issue. What else can I do to correct this.
Pulled the flywheel and the key was sheared. Replaced the key, put it back together and she started up. But now the other head is dumping oil into the muffler. Blowing massive amount of blue smoke. Oil was actually dripping from the bolt that the exhaust bolts to the head.....FML! I'm assuming the rings are shot.
