Anyway, that is more than enough ranting. The short summary is, I think the most practical way to build your high performance Victa is to get hold of a standard set of hot-up parts that have been designed and documented by someone else who spent a lot of time and money doing it.
Im with Grumpy.
Sorry but i missed the purpose of the excersise. Is it just to mow grass???
Personally i would say that a full crank Victa has more than enough standard to mow as fast as i can push short of jogging. Well thats 'Lawn' mowing. If you were cutting grass you would use something else, something like a Super 24 which even with the same Victa motor on it has enough HP to chew grass nicely.
Bob.