Kohler 12.5 command will not run

Devil Dog

LawnSite Member
Location
Pennsylvania
I replaced the oil pan on my Kohler 12.5 command model # CV12.5S. Now it will not run. If it sits for a little bit it will it fire off for a second and then die,. If you crank it after that it will backfire through the exhaust and the carburetor. I figured the timing might be off so I pulled the motor and pan again this time one of the gears came off with the pan so couldn't verify if it was in time. I lined up all the timing marks and put the pan back on.
Same problem still, it still backfires through exhaust and carb. I pulled the carb cleaned it and didn't help. New spark plug installed still no. Timing light hooked up to it shows the coil is firing. It won't even try to start with choke on. I have to turn choke off to get it to start for those few seconds.

P.S Sorry if confusing to read and the run on paragraph just writing as I think of things
 
OP
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Devil Dog

LawnSite Member
Location
Pennsylvania
Thank you for the link. Reading through it looks like I got everything in properly. But will pull the pan off again and recheck.
 
OP
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Devil Dog

LawnSite Member
Location
Pennsylvania
Maybe a stupid question but what stroke should the engine be in when the timing marks are aligned? Watching the exhaust valve as I turn the engine it is finishing the exhaust stroke and starting intake when the timing marks are aligned. Trying to figure out if the cam gear is somehow 180° off. Or is there no way for the gears to be off if aligned with the marks?
 
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JoeRagMan

LawnSite Senior Member
Location
Near TMI
Crankshaft makes two revolutions for one revolution of the camshaft. If the timing marks are aligned, that is good to go. Next question; did you adjust the valves per manufacturer's procedure after installing the camshaft? I do not know if this engine has compression release, because if that is not installed properly it could keep the exhaust valve open. Potentially would lose compression and cause a backfire out through the muffler. Do you have a leak detector to check compression? If not sure how to perform that test go to YouTube and do a search. That test would tell you if the engine has a compression issue. Please keep us updated, good luck.
 

BigFish

LawnSite Fanatic
Location
chesapeake, va
Look, fer Kohler manuals, I always use the Kohler site.
https://kohlerpower.com/en/engines/manuals
Just scroll down to find yer motor.
Ya want the CV430/CV13 service manual.
All the timing info will be in the man.
Should tell ya how to do a leakdown test also.
IDK if yer motor has hydraulic lifters, but, iffen it does, you need to be very careful with the bleed down/adjustments.
 
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Devil Dog

LawnSite Member
Location
Pennsylvania
I never removed the cam so I didn't mess with the lifters. I did pull the valve cover and it appears both valves are fully opening and closing. I pulled the pan again and rechecked the timing marks and it was still in time. So I don't think it's an internal engine problem. Gonna try and remove the flywheel and see if maybe it sheared the keyway and is off a little bit.
 
OP
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Devil Dog

LawnSite Member
Location
Pennsylvania
Pulled the flywheel. Keyway is good but there was a a buildup of dirt and grass in the magnets on the bottom. Cleaned it out and blew the stator clean. It will now struggle to run on choke but die as soon as I take it off. I tried to upload a video but not sure if it took it.

Edit. Used a video site so hope this works
 
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OP
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Devil Dog

LawnSite Member
Location
Pennsylvania
Update: mower is running :)

I started it in choke and let it do it's spitting and sputtering for a little bit and kept working the throttle down to get it off choke and all of a sudden it just decided to roar to life. So I don't know exactly what changed or why but this thing has been driving me nuts for the last week so I will take an unexplained miracle fix. Lol
 

hort101

LawnSite Fanatic
Location
S.E. New England
Update: mower is running :)

I started it in choke and let it do it's spitting and sputtering for a little bit and kept working the throttle down to get it off choke and all of a sudden it just decided to roar to life. So I don't know exactly what changed or why but this thing has been driving me nuts for the last week so I will take an unexplained miracle fix. Lol
Sounds to me like a carb issue and juggling the choke cleared its throatThumbs Up
I do that on my 1 stroke stuff often
 

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