RE: OS61 Max SF
Pjtrax,
If this engine has no sentimental value to you (and I suppose there is very little reason for it to), just get a replacement engine...
The normal SF was never considered any 'OS paragon'...
You can easily obtain a new ABC .61 engine... A Magnum will cost you $105 (less as the ASP), an ST will cost $100, a Tower will cost you $90...
The Magnum/ASP are essentially OS SF clones, made by Sanye, with a much better, true ABC construction.
Going into all that trouble and cost of finding parts for this defunct engine, will not reward you with anything better than cheaper engines you can buy new...