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What's The Clatter?

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That is, what is the clatter in my 'new' 27 HP Command in my Sunstar. I got a decent Sunstar with a tired Command from my local Simplicity dealer several years ago. A couple or three (or more) years ago, I found a 25 HP Command short block on eBay and collected/bought the other stuff for a 27 HP Command - a correct spec crank for the Simplicity Sunstar (same crank stroke works for all 18 - 27 HP Commands), used heads (25 -27 HP's have a different bore and therefore different head PN's than 18 - 22 HP’s), a new 27 HP cam, and the newer ignition components. The short block was the first design 25+ HP block that did not have cast iron cylinder liners. I also added a 25 amp stator.

First surprise was the used 25+ HP heads I had acquired on eBay were for a vertical Command engine and were not the same as the heads for a horizontal engine. While either set of heads will bolt to either block, the oil drains for the valve train area is different in both the heads and the blocks. When the rocker area fills with oil, it drains through the valve guides into the intake and exhaust ports. That was messy, smoky, and a bit embarrassing! So I bought proper new heads along with new valves and new valvetrain hardware kits from Kohler. Put everything together and back into the Sunstar.

Then I got distracted by job, life, medical issues, SWMBO, etc, etc. I finally got back to this project recently. The first problem was a new problem with the Sunstar electrical interlocks. I have resolved that well enough that the Command now runs when the hydro lever is moved out of neutral. Spent some time getting the governor/throttle/choke adjusted so the Command will start easily and idle nicely at 1500 - 1800 RPM per Simplicity/Kohler spec. So then I let it run and warm up for a while before the final high idle adjustment. After 15 - 20 minutes, I started hearing a clattering noise from the left valve cover area.

I quickly shut it down, suspecting I hadn't torqued something in the rocker area properly. I took off the valve cover and both rocker arm bolts were snug (I THOUGHT I had torqued everything properly). Then I fired it up again. The clatter had gone away but it returned after a few minutes.

Whiskey Tango Foxtrot!!!

Any ideas about what’s going on from you experts. I do have an idea, but I would like to hear from you before I try to mislead you.

Thanks in advance.

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Hydraulic lifters or solids? If hydraulic, they could have pumped up during running to be too tight now, especially if you did final rocker adjustment prior to running. Had this happen on a car once when I installed some new lifters. Don't know about your engine! Thought I'd share my experience.


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Ron, everything is seated correctly. Ran it only briefly with valve cover off because of the mess but it looked OK. I suspect if something were wrong in that way it would not idle smoothly.

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