Well done mate.
Been keeping an eye on this thread - Ive just finished stripping down one of these engines. Just logged in to offer a replacement carb for you (I have several).
If youre thinking of getting into fixing up mowers remember:
Keep It Simple!
Fix the easiest problems first - 90% of the problems I fix on a daily basis are carby blockages or just old fuel.
If the engine wont rev or surges (revs up then down) in your case now I would strongly suspect just a blocked air filter. They have a foam pre filter on them try cleaning out that first (I just wash them in the old petrol I drain from the tank) and smack the paper filter on the ground to loosen up the crap (If you have an air compressor handy give it a good blow out), dry the pre filter, reinstall and see what difference that makes - I'm positive that'll fix your engine. The Air filter doesn't need to be changed EVERY service but does need to be cleaned out thoroughly.
Good luck with the mower!
Pete
