Mule 610 KAF-400
 

Guys, I really need some objective eyes on this issue.
A while back, my mule was idling while I was doing some quick work and it shuddered and shut off but, wouldn't start back up. I added some fuel to it since it was low but, it made no difference. Still wouldn't fire.
It was acting like it wasn't getting any fire. I pulled the plug and connected it back to the plug wire and positioned it with access to a ground. Spun the engine over and verified that I had fire. Reinstalled the plug, disconnected the fuel line, spun it over and verified that the carb was getting fuel. Still wouldn't fire. Pulled the carb off of it and drained the bowl to ensure it didn't have trash in the carb. Sprayed carb cleaner through all the ports in the carb to ensure none of the internal ports were blocked. All of the ports were open. Reassembled the carb and reinstalled it. Spun the engine, still no fire. Pulled the air cleaner snorkel off of the carb to ensure it was getting adequate air flow. Spun the engine, no fire. I broke out starter fluid, fogged it toward the carb snorkel and the engine lit up momentarily. Checked the carb to ensure again that it was getting fuel and it was. I tried a separate container of fuel to eliminate bad gas, still no fire unless lit off with starter fluid or carb cleaner.
I ordered a new carb and fuel pump, installed, still no fire.
It appears the pump and carb are getting sufficient vacuum to operate properly.
I'm absolutely stumped here.
Not sure what else to check or where else to look.

Any other ideas would be appreciated.

Thanks

Mule 610 KAF-400 Update
 

I've been unable to find any other reason for this behavior so my latest attempt to resurrect this unit involved doing a compression chk.
I expected to see a reading of at least 100 - 120 psi. What I got was a 65 psi reading.
It appears that there might be a stuck valve or something else going on in the head such as a head gasket. If it is either one of those issues, a new head gasket will be installed after I pull the head and get the issues resolved.
Once this brutal cold streak ends, I'll pull the valve cover off and check the valve lash to see if that is the root of the problem.
If I don't see anything out of sorts in the head, it will point to something deeper in the block, piston or problem with the rings.
So, now, I'm hoping for valve issues.....

Final update. Weather broke and managed to get down to removing the valve cover and check the clearances. Seemed a little tight on both valves.
I backed off on both of the valves about 1/4 turn. Hit the ignition, and BOOM, she lit right up.
WOW, my mind was blown. The fact that the valves had tightened up over time to the point that they couldn't hold enough compression and create enough vacuum to pull fuel through the carb, just never crossed my mind. So, I went about properly adjusting them and when complete, the throttle is crisp and sharper than it has been since I've owned it.
I never would have thought this could be the issue.
After doing some research on it, it appears that with this unit being an air-cooled engine, over time the valves hammering the valve seats, they tend to gradually shift from the original position, causing a gradual but increasing larger gap, thereby causing it to gradually lose compression and therefore vacuum.
Who woulda thunk it..........?