D100 Ran, Died, Crank-No Start, Loose Rocker, One Valve Not Moving

Hey guys and girls. Looking for some help. I've searched around but can't find a problem quite like mine so here goes...2011 D100, 17.5HP B&S. Mowed the other day for about 20 minutes with no issues at all. All of a sudden, she starts running rough, I lose power, get some pops through the exhaust and she dies. After multiple Crank-No start attempts, I thought maybe a fuel issue (about 1 month old). Drained all fuel, replaced with new fuel, new fuel filter, new plug also. Still Crank-No start. Decided to push her back to the house. After reading on this site that similar symptoms were experienced with out of spec rocker/valve clearance, pulled the rocker cover and sure enough, top rocker had about 1/4" of clearance. The stud had backed out. So, tightened the stud, and started to set the clearance. Removed plug and turned engine by hand. As I was turning the engine over, the top valve moved in and out. The bottom valve did not move at all. I suspect this is the problem. What would be broken internally that would prevent this valve from moving? What is my next step in getting her running again? Thanks in advance for any help and sorry for the long post. Just wanted to include as many details as possible.

-jfaulk

I dont think its a problem internally. I think its a problem with your head(the one on the mower). The valve seat behind the rocker that wont depress has backed out to the point that the valve wont open. Verify this by looking through the valve springs to the metal ring around the valve stem. If one is backed out so much it wont allow rocker to depress then thats the culprit. This is caused by overheating. To prevent this take flywheel cover off engine and clean cooling fins around head. Best way to fix is to replace head.

Thanks, dfbroxy. I think that's it. I'm going to try to get a new head this weekend. I will post back with my results. I appreciate your info and explanation.

Post 2 describes what happened to my John Deere 100 about 2yrs ago. I just bought a new head. Some folks will just press a new valve seat into old head and then pin punch the head around it to squeeze it tight. But I just put a new head on it. I found one local for $220. I heard this valve seat loosening is a fairly common problem on older JD's.

Edit add -> My seat was out so much that the valve would not shut and no compression at all. The motor just spinned freely when I let off the starter.

Re: D100 Ran, Died, Crank-No Start, Loose Rocker, One Valve Not Moving-UPDATED

Just wanted to update my progress. As dfbroxy stated, the valve seat had backed out of the cylinder head. I replaced the head this morning. She fired right up on the first turn of the key. I also changed the oil, oil filter, air filter, fuel filter, spark plug, added a fuel shutoff valve, cleaned all the cooling fins, and drained my fuel tank just because it needed it. Thanks to all who posted.

One more thing to add, keep the transmission and the fan above it very clean. They are prone to get covered in grass clippings and overheat and fail. If you want some incentive to do so just look up the price of a replacement k46 trans. If it is a 2011 model and still has the origional trans in it consider changing the fluid in it to synthetic 5w50.