king1 0 #1 Posted November 13, 2009 i have a c125 with a 12 hp kohler. i got it real cheap and the guy i got it from said it needed some tinkering. it would run for about 10 min. then spit and sputter and die. he thought that it was the carb. he had one that he gave to me and i put it on and it ran ok for about 2 or 3 mowings. it would die occasionally. today i put a new battery in it and tried to get my final mowing in and it started to act up. it would do what he was having problems with, run good for about 5-10 min and then spit, smoke, sputter, and die. it will start right back up but it won't run long under a load. it will idle no problem, it will run at full throttle no problem, it will run at full throttle with the deck going, but when i start to put drive it with the deck going it will really strain and then die. Any idea's? Share this post Link to post Share on other sites
Ken B 3,116 #2 Posted November 13, 2009 Heres some things too check, make sure your points and condenser are good. Make sure the fuel line and filter are clean and free of blockage. I've had exhaust valves stick on k301's when they get good and warm and the motor will start too run really crappy. A little marvel mystery oil in the fuel will help there. Also, make sure the head gasket is good. If you don't know when the last good tune up was ya may as well start there. Share this post Link to post Share on other sites
mcdarbyc81 1 #3 Posted November 13, 2009 i had the same problem but put a new spark plug in and runs fine hope it helps ya :notworthy: Share this post Link to post Share on other sites
WH nut 553 #4 Posted November 14, 2009 A bad condenser will do that also Share this post Link to post Share on other sites
qd-16 14 #5 Posted November 14, 2009 Fuel cap vent blocked?? Share this post Link to post Share on other sites
gregg.d250 0 #6 Posted November 18, 2009 Many K-Series Kohlers will lose compression and shut down as the exhaust valve stem expands and binds in the valve guide while under a load. The exhaust valve effectively sticks open a little (similar to how the ACR system works), then gets even hotter as it can't close and transfer the absorbed exhaust heat from the valve face to the valve seat on each firing cycle, and the stem expands further, causing the valve stem to freeze in the guide even worse-- holding the valve open more. You now have no compression and the engine shuts down A few minutes later after cooling down, the engine will start and run like nothing ever happened. If this only happens under heavy load, I would tend to think this is your problem. It sounds like you've ruled out fuel and possibly ignition issues at this point. Marvel Mystery Oil in the fuel seems to be a fix for this. Lead Substitute is also a good additive to run in the older engines, as it prevents the exhaust valve from 'welding' itself to a non-hardened valve seat on each exhaust cycle. Basically, preventing seat erosion-- and does help with the valve guide issue I believe you're experiencing. Try the MMO and Lead and tell us what you find. :notworthy: Share this post Link to post Share on other sites
gregg.d250 0 #7 Posted November 18, 2009 Oh - and BTW - check your valve lifter clearances. On a K301AS, it should be .008-.010" on the intake and .017-.020" on the exhaust. Check them when the engine is cold. Share this post Link to post Share on other sites
linen beige 14 #8 Posted November 18, 2009 All the other posts are very good ideas, but I gotta ask... Are the cooling fins on the block clogged up with crud? Share this post Link to post Share on other sites
rickv1957 70 #9 Posted November 18, 2009 Is it possable your coil is bad as they will work fine untill they get warm and break down,Rick Share this post Link to post Share on other sites
