Weird one! I'm stumped with my Ariens snowblower. (video)

[jlatenight]

Hi guys, so it's acting like it's hydrolocked or something, but it's not. When I pull the cord, it rotates smoothly until I hit a point where it locks up and is really hard to pull. You can, but it's too hard to be able to start it. Here's a video of it: The pauses are when it hangs-up. This happened kind of suddenly while blowing recently. Not really sure of the chain of events really. It ran out of gas, I refilled it, then I couldn't start it. If I take the sparkplug out, smooth as can be. Put it back in and the pull start catches then once you get over that "hump" it pulls smoothly maybe one or two rotations, then you hit it again. Must been when the valves are in a certain spot. I can hear a quiet hiss of air out of the exhaust . Not sure if it's in or out. The electric start's the same way. It jams when you try to start it, but if I get the pull rope to a good spot, then use the starter it fires right up and runs relatively fine. Runs a little rough, but nothing serious and sounds better under load. choking it more doesn't help. Oil level is where it should be, and I tuned the valve lash to proper specs. Anyone have any thoughts?

 

[jlatenight]

Welp, after a ton of research, I found it's the pressure relief mechanism, which is usually on the camshaft. It's activated when you first start the motor so a little bump is added to the cam to add an additional movement in the intake valve to release pressure, then releases or retracts once it's started by centrifugal force. Explains why it runs ok if I can get it started.