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Tractors
ed_luna41

Kohler CV16s won't start after replace rocker arm hold-down bolt.

Ed Luna
hace 3 años

I've owned the Scotts lawn tractor with a Kohler 16 hp since new. Last week while mowing at full speed the engine suddenly stopped while making a sound very much like a valve had let go.


I pulled the rocker cover off and was pleasantly surprised when I found that the 6mm bolt that holds the rocker arm to the pivot point had snapped and the rocker arm was detached. I ordered the bolt from McMaster Carr (bag of 50 for 10 bucks +shipping) and when they arrived I reinstalled the rocker and cranked the engine to make sure the valves opened on closed properly... which they did. I reassembled everything and went to start the engine but no joy.


Cranks fine but will not fire. Sprayed starting fluid directly into the carburetor with no change... no combustion at all.


Pulled the plug and checked for spark... plenty of spark but I couldn't vouch for spark when the plug is installed and under compression.

Took a compression test and got 60 psi... seems low to me but the compression release mechanism at cranking could be causing that.


So there you have it... from running fine to will not fire after the bolt that holds one of the rocker arms broke. God knows what other damage may have resulted from a valve staying closed with the engine at just about full throttle but clearly something has.


The 60 psi has me a little concerned and if it were one of the hundreds of car engines I've worked on (currently rebuilding an '83 Mercedes 380sl) I would have already pulled the head but I wouldn't want to pull the head just on speculation over 60 psi. when I don't know what the compression should be.


bTw... the engine has hydraulic lifters, an oil filter, overhead valves and must have an oil pump to get oil through the hollow push-rods to the rockers.


Any suggestions would be greatly appreciated.

Comentario (1)

  • PRO
    Kevins Small Engine and Tractor Service
    hace 3 años

    Hi, So you have done well covering the basics so let's move on to other possibilities. While your compression is low, it is enough to run, you have fuel and spark and compression. My next question to you is why did the rocker arm nut fail suddenly? Plugged lifter? There are two head designs on the 16 HP Command, one with non-adjustable rockers with a single nut that is simply torqued down on the head and the valve spring will compress the lifter correctly and the other has adjustable valve lash which requires the lifter to be fully compressed then setting the valve lash to spec. I assume you have the first. Did you torque the bolt per Kohler spec and ensure the valve was fully closing after allowing 15 minutes or so for the lifter to compress then re-check valve closure? Second, I would be to pull the engine cover to check the flywheel key or simply check that the flywheel magnet passes by the coil just a bit before top dead center via placing a screwdriver in the spark plug hole to confirm TDC. That engine also has a digital spark advance control box that retards the timing based on feedback from the coil module but it is likely functional as you do have spark. Summary; pull the valve cover and ensure the valve is fully closing, pull the engine cover and check the flywheel key. Let me know your findings.


    Kevin,

    Kevins Small Engine, 03908

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