Mower deck Husqvarna Z254 - belt shakes very badly and engine tries to die when blades engaged

[veekay]

Remove one spark plug and rocker cover.
Rotate the engine so that cylinder is bottom dead centre on compression stroke.
Feed as much nylon rope ( plated rope is better ) down the plug hole as you can then rotate the engine to compress the rope.
That will hold thee shaft while you tighten the bolt the turn the engine back a little and pull the rope out.

Thanks. I have to ask though, what does a rocker cover look like?

 

[bertsmobile1]

It is the tin cover on the end of each head that you take off to check the valve lash .
You need to do that so you can see the valves to work out if the piston is on compression ( both valve closed ) stroke.
So while you are there, check the valve lash at 1/4" past, should be around 0.004"

 

[veekay]

Got my correct belt. I adjusted the clutch as noted, but think it may still be too loose. How freely should it spin when turned? The clutch as well as all the blades turn very easily with the belt attached. It also takes a while to stop the blades once disengaged. Too loose?

I also noticed when I replaced the belt that the other one was almost shredded in half - this after just two hours.

 

[veekay]

Got everything back up and running pretty perfectly. I apparently adjusted the clutch wrong and didn't measure between the two actual plates and instead measured between a plate and the metal frame, which made things super loose.