Overpumped valve lifters/lash adjusters on Command CV12.5S single cylinder

cmw

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  • / Overpumped valve lifters/lash adjusters on Command CV12.5S single cylinder
I have a 12.5HP Command CV12.5S single cylinder engine that I have been using in a riding mower converted to a small utility ATV that I pull a small trailer with. I was moving some firewood and having a hard time keeping the engine running. Then it stalled and lost compression. I could tell something had happened in the valve train and waited until a warm day (today) where I had time to pull the valve cover off.

Anyway, the two bolts that hold the pivot pin that holds the rocker arms had come loose and one finally broke off. I bought two new ones of the correct size and class 8.8 of course, cleaned everything up, used Loctite this time, and put it all back together. I could tell that the lifters were overpumped as I had a hard time getting the pushrods in position with the rocker arms. Apparently the engine ran long enough like this and the lifters pumped up to take up for the extra lash caused by the bolts coming loose. The valves will not close now that the rocker arms are mounted correctly and closer.

Will these bleed down on their own if I just leave the thing sitting overnight or for a few days. I was going to try to start it and just let it sit at a slow idle for a while but the valves cannot close because of this situation and the engine spins very fast and freely because it has no compression. I wasn't going to use it as I figured I would burn a valve with them not closing all the way but I cannot even get it to try to start. There is simply no compression.

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cmw

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  • / Overpumped valve lifters/lash adjusters on Command CV12.5S single cylinder
I went back out a little while later and turned the flywheel with the palm of my hand and could feel the resistance of compression so cranked it over and it started. I let it run on a low idle for 10-15 minutes and then started using it like normal. I could tell it was running better than it had been before it came apart on me so I suspect those bolts had been working loose for quite some time. It would have intermittent misfires and LOUD backfiring from time to time so I suspect that was all related. Anyway, all seems well for now.

This thing is like parts from 3 separate mowers I salvaged from the junk pile so not too bad.

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7394

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  • / Overpumped valve lifters/lash adjusters on Command CV12.5S single cylinder
Others may have a different opinions, but I'd think about adding a correct portion of Seafoam* to the crankcase oil to try & clean the lifters out.
They may be may be slightly gummed up. I would change oil after doing this as well.

Just my .02
 

cmw

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  • / Overpumped valve lifters/lash adjusters on Command CV12.5S single cylinder
I changed the oil and filter after fixing this problem and getting it running. It was getting to be time to change anyway and I always like to change the oil after I have any engine opened up such as having the valve cover removed.

This wasn't due to dirty/sticky lifters. It was because the bolts holding the pivot point for the rocker arms in position had started to back out, allowing for additional lash. The hydraulic lifters did what they were supposed to and pumped up with more oil to take up the gap this was creating. Obviously the pushrods would have just fallen out of place this had all happened at once. That is what finally happened when the one bolt finally broke from being loose and the engine just quit at that point. Somehow there was no damage to the pushrods or rocker arms.

I run the Rotella T6 5W40 synthetic oil in all my riding mower engines. I have two other Kohler Command 16HP single cylinders that came to me after being severely neglected. The oil looked like tar, the lifters were clattering, and the engines were consuming quite a bit of oil and smoking, especially under load. I changed to the Rotella and these were like new engines after one use. The new synthetic oil looked dirty after one mowing so I changed it again with a new filter. The clatter went away, the oil burning slowed to where I cannot see the level drop on the stick between changes, and the oil doesn't even look dirty after a hard season of use. Obviously this oil really frees up sticky rings and lifters. It is a diesel rated oil so has a lot of detergents.

I know a lot of people swear by this oil and I am one of them. I ran a blue STP oil filter from Autozone as this engine needs the shorter filter and this was the only one I could find. How are these blue STP filters?

As for the mower, I have used it several times since and it has worked without a hitch. The little 12.5 HP can pull a big load of firewood without trouble at all. The big load on these riders is really the mowing deck cutting through the grass.

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7394

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  • / Overpumped valve lifters/lash adjusters on Command CV12.5S single cylinder
Reading lots of great reports about ppl using Shell Rotella.
 

cmw

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  • / Overpumped valve lifters/lash adjusters on Command CV12.5S single cylinder
Reading lots of great reports about ppl using Shell Rotella.

I think this is great stuff. I have run it in several engines calling for 5W30 and 10W30 and had no issues. I run my stuff hard and it seems to do the job. The Kohler Command is also a great engine. It is too bad they made the Courage. Everyone of those I had has failed in one catastrophic manner or another but the Commands just keep on taking the abuse and come back for more.

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7394

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  • / Overpumped valve lifters/lash adjusters on Command CV12.5S single cylinder
I called & spoke to a Shell Rotella tech, & they told me they use a lot of ZDDP in certain weights, which is ideal for solid lifters & /or just keeping things slick internally.
And to be sure & check the date on back bottom when oil was bottled, If date is older than 5 years, they do not recommend using it.

But I believe most all oils have a bottled date on back too, I know Mobil 1, Castrol & Kawasaki K tech oils do.
 

cmw

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  • / Overpumped valve lifters/lash adjusters on Command CV12.5S single cylinder
All my oil was bought within the past few months so it is new unless it was on the store shelf for a while.

Anyway, the engine in question decided to call it quits again and this time I think it was for good. Some internal failure occurred and it lost power and rattled to a stop. The engine is locked up to where I cannot turn the flywheel by hand. I pulled the valve cover and it isn't a valve train issue. I will remove and dissect the engine but I think it is toast.

I got a couple good hard years of use out of it and it appeared to have been neglected before I got it. The oil was like tar and it took two changes to clean it out. I think the engine was just worn out and gave it up. I have to say it did well for the condition it was in and how hard I have used it. This is the first Kohler Command I have ever had with a non-repairable blow up. These are solid and tough engines but can only take so much like anything. I am sure it could be repaired but it isn't worth it.

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bertsmobile1

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  • / Overpumped valve lifters/lash adjusters on Command CV12.5S single cylinder
Desel oil works well in air cooled engines.
A lot of vintage & classic bike riders are now running Rotella ( or similar ) as zinc is being phased out of most motor oils
Deisel oils are very highly detergent so if there is sludge laying around in the engine, it will get held in suspension making the oil go very black very fast.
As diesels run hotter than petrol engines they also have a more suitable temperature profile for air cooled engines.
 
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