Hi guys, I hope you don't mind me bombing in here looking for help.

I've picked up a 93' power torque Victa that's over revving and doesn't idle. I know this is a fairly common issue and I've looked at all the common fixes.
I've checked the carb manifold o rings and the top case o ring, they seem to be in very good condition. I've pulled the carb apart and found two brass washers under the governor. I couldn't say if they were installed as a last ditch effort to get this thing to run or if they've been there for ever. Regardless, they're in there. I read here and on other forums that there is rarely a need for more than two washers.
If I squash the rubber inlet hose the mower calms down. So, an airleak seems to be the problem.
The only seal I haven't eyeballed is the lower crank seal, under the flywheel.
I thought I'd ask for a second opinion before I went pulling the rod, piston and crank out to possibly find a perfectly good seal.
I also haven't looked at the vacuume decomp, other than to suck on the hose to confirm that the valve closes. It does. Can this be blanked off to test?

Oh, this mower is for a kid in my street who wants to try making a few bucks after school mowing lawns. I only paid $15 for it and other than being covered in dirt it's in really quite good condition. I'd like to get it running nicely, no point in giving this kid a dud gift.

Really appreciate any help.