Riding mower ran too fast, now backfires and hard to start

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mapleguy

Member
Kohler CV15S engine on my old Sears riding mower. Was running fine, then suddenly I noticed it was running really fast and power was missing. Shut it off and it backfired before re-starting, still was running full out. I checked the timing because of the backfire but the shear key is fine. Searching online it seems that the interior part for the governor is broken. After it cooled, I tried to start again to try to confirm the problem, but now it just backfires and I can't get it to run. Would this be typical of a broken governor or is there something else to check first before I open it up? Thanks.
 
Thanks ILENGINE, I didn't even know these engines had hydraulic lifters. If it is over pumped, will it bleed down after sitting for a while or do I need to replace it? Is there a relatively easy check to see if this is a problem, like removing the valve cover to check for valve opening and closing?
 
Normally they will bleed down, but on occasion they will fail and overpump causing it to hang the valve open. Issue can also happen with using too high a viscosity oil during cold weather. Have come across issues with people using 30w below 50F causing over pump
 
mapleguy said:
Kohler CV15S engine on my old Sears riding mower. Was running fine, then suddenly I noticed it was running really fast and power was missing. Shut it off and it backfired before re-starting, still was running full out. I checked the timing because of the backfire but the shear key is fine. Searching online it seems that the interior part for the governor is broken. After it cooled, I tried to start again to try to confirm the problem, but now it just backfires and I can't get it to run. Would this be typical of a broken governor or is there something else to check first before I open it up? Thanks.
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Remove valve cover and visually check valves for any problems such as push rod bent, etc.

Start engine and hold the governor arm so it doesn’t over speed and see if governor is fighting back or not. I have to go in deep on my Vanguard 35 hp next week for a bad governor.
 
The pushrods look fine and the motion of the rockers looks typical. I took out the engine and removed the oil pan to find that the governor is not broken. Reinstalled the engine and checked the compression and only have about 15psig. I guess the low compression could cause the starting problem, but I don't really understand why the problem seemed to begin with an over-revving engine. Would you suggest replacing the piston rings to fix the compression issue?
 
You could loosen the rockers arms and check the compression again. To see if the lifters a keeping the valves open.
 
mapleguy said:
The pushrods look fine and the motion of the rockers looks typical. I took out the engine and removed the oil pan to find that the governor is not broken. Reinstalled the engine and checked the compression and only have about 15psig. I guess the low compression could cause the starting problem, but I don't really understand why the problem seemed to begin with an over-revving engine. Would you suggest replacing the piston rings to fix the compression issue?
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You need to do a leak down test to pinpoint problem. 15 psi compression is nothing and engine will never start or run. Also, did you visually inspect piston, rings, and cylinder while engine was apart?
 
Good idea to loosen the rockers and recheck compression, I am learning a lot from you all. I'll do that test when I get a chance.
Since I did not remove the head or cylinder, I did not visually inspect piston, etc. With the oil pan removed I did not see any metal debris. I did manually turn the crankshaft and observed that everything I could see (connecting rod, bottom of piston, etc.) seemed normal.
Thanks for your help.
 
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