Hi Aerrow,
A warm welcome from myself also to the ODK forums.
What you have is one of the first issued Model 45's, if that's the original engine. It shows that the engine was produced in May of 1968 which was the year that the 45 was introduced. I'd say that the mower itself was build around August / September of that year. I does though show signs of repainting at some stage as it's no longer showing it's initial "Alpine Green" colouring.
Now as far as get it going reliably one must start with the engine itself which it seems you've already made a start on. These particular 60102 engines run a very simple carby and all one must do is thoroughly clean out all internals of gummed up old fuel. Throttle body cleaner is a good solvent to use via a long tube nozzle fitted to the to of the aerosol can. Also the tank will require a good clean out. The gasket between between the the tank and carby must be in good shape and if in doubt "throw it out" and replace it so as to avoid air being sucked through the joint. Also the thick gasket between the manifold and head assembly must be serviceable and not allow and air leaks to be encountered. After that it is merely about compression and spark. As you've had it running has eliminated the spark issue as that's been demonstrated to be there, so that only leaves compression. Sadly this is the department that has had time and wear and tear take it's toll of this requirement. Normally these small engines can be rather easily revived but many have taken the option of replacing the power plant with a far more smoother new style Briggs engine, something that I'm doing currently to a similar powered 14 inch Scotty for a friend.
Generally these old 60102 Briggs & Stratton power plants only require a new set of rings and a light honing of the Aluminium bore by hand to give these old girls a second chance at life along with a valve grind and resurfacing of the valve seats to gain full compression again.
I guess that's enough for now.
Cheers,
BB.
