I finally got around to test starting it today and have encountered problems. First, I had forgotten it was leaking out the primer cap, so replaced the O ring.
Then when I tried again I find it only starts in the run position and only runs very high or not at all along with momentary stalling and backfiring. I did notice the throttle control lever moves a little too freely for what I'm used to. Any ideas? It sounds like a carburettor tear down will be required, or is it possibly to do with the decompressor valve?