Hi JRC
I also have had this problem with my Victa Powertorque. It is still there, but it is very minor rev, I think I need a new throttle kill wire rubber, and governor diaphragm as one edge is a little squashed.
Here is what I did:
Clean carby (especially main jet), and add 2 brass washers under the throttle cam (3 too many for me, but maybe not in your case). Much better.
Turned poppet valve in carby, so the B is where the C was � this makes it richer (refer manuals section), but the change wasn�t that noticeable. It did pick up rpm better though.
Then I replaced the o ring on each end of the plastic intake manifold, and the one under the starter mechanism.
I also stuck a piece of wire down the port the vac hose attaches to (on the block next to the flywheel). I thought it might have clogged up and changed how the governor works.
I then took the exhaust off and cleaned carbon out of the exhaust port � I thought it was worth a shot if it was stuffing up back pressure.
I did the last few things all at the same time, so I don�t know which one made the most difference.
As far as I know, the governor works by pulling the throttle closed � that is, it�s making sure the poppet valve doesn�t fall all the way open. When the motor slows down (heavy grass), less vacuum is created, and this allows the poppet to drop and rev it up again. If you have a vac leak (eg split diaphragm) or insufficient vacuum signal (blocked vacuum port), then maybe there isn�t enough vacuum at high rpm when the engine is drawing the mixture hard (and pulling the poppet valve open by itself).
Checking this is probably the quickest � just don�t snap off the plastic connector on the carby.
Regards
Tyler
