Yes I can get a 31R907-0007-G1 (17.5) which list for $571 to replace the 2008 18.5 rated engine which might be fine since the old engine is on the old rating system for more than twice the price of the current parts needed. The problem is how close was the old engine actually to the labeled HP. Still I would had recommend the more powerful engine as I done ran into this with one my 42" mowers that had a 310000 series that just barely was able to cut grass and this Husqvarna 42" would have the same problem and needs a true 18.5 or better engine. This would be the 33S877-0019-G1 (19hp) Promo engine which lists for around $623 plus an hour labor to put it on and wired it up properly.
What had got me on this engine was the pieces of the valve seat where in the muffler and I hadn't removed it. When I was turning the engine over accessing various areas they worked they way back into the exhaust port into the engine. Jamming it again once the valve had opened. Kinda lucky it did it. I would not had known until I had everything bolt down and attempted a start-up. It is first time I have ran into this kinda problem in a long time. Usually with a valve seat problem the engine still turns most of the way turn if pieces are in the cylinder and stops but this had done few complete turns after I got the stuck rod and counter balance link freed but I didn't have the camshaft and push rods in place before I was re-assembling the engine yesterday. This is what I get for thinking that the stuck rod and counter balance links to be the root problem caused by the destroyed plastic plug of the counter balance weight.
Sometimes surprises shows up on a repair and boy this is a big one and caught me off guard.
And I am
at myself for letting the engine do it do me.
The truest measure of society is the how it treats its elderly, its pets, and its prisoners.