Indeed I have played with various pump element sizes - And found that the best all round for performance and speed governing tended towards the largest element I could get...
Smaller elements had a tendency to be lazy on the governor, as well as cause a greater amount of carbon build up in the cylinder when running crappy fuels... There was marginally more "ignition knock" with the larger element when timed correctly for the RPM desired....
Further, I experimented with everything I could lay my hands on spring wise for determining best governor responses...
I ended up with a basic formula of spring length un- tensioned, at rest, being 3x the length of the lower end of the bellcranks total travel as its shortest, to 6x the travel length at its longest.... The spring wire diameter does make a substantial difference, but that being said, the average best wire diameter I found was between .8 and 1.2mm and the nominal coil diameter was around 10 to 12 mm... Wide variances I know, but with not all springs having the same wire hardness (thus changing the forces they can exert over a given pull distance), there is a fair bit of leeway for playing around....
The easiest thing I found was to get 2 identical springs, set one up and start trimming until the response is satisfactory, or best with that particular grade of spring... If you overcook it and trim too much, slap the other one in and don't tighten it till it breaks....Lol.... Trimming off one or two coils at a time was a tedious, but rewarding job ultimately.... Also, I swopped the mounting/adjustment points round for better running too... (as well as getting a nice long adjustable area to work with)...
Some crappy pics below ..... (Not the ideal spring, but what I had on hand at the time.... It holds to around 51Hz unloaded through to about 50.5 when loaded to 3Kw or so...)
Cheers
Ed
PS, the silver tank is an auto oil top up I made and installed..... Keeps the oil up to max level, unattended while running long and extended periods.... It can be filled up during running too, by closing the tap, opening the top plug which has a dipstick attached to it, topping up the the tank, closing the top plug then re-opening the tap....Think its worth a patent application?
....Naah...
If you like it, use it!!
Edit... Oops, forgot to mention.... the crappy pic of the IP rack shows a weak spring I installed to take the slack out of the linkages and further improve governing tremendously... It also provides the peace of mind that should a link fail, the rack closes automatically... Additionally, there is a nut that allows the opening limit to be set to prevent "dirty black specs" on clean washing.... Nuff said!