Wow, thanks for all the informative replies.
The B&S motor doesn't use much oil or blow any smoke, so I suspect the rings are not too bad. I'll investigate the possible carby issues that a couple of you have mentioned. If the poor cold starting is nothing more than a malfunction of the choke or enriching circuit, it might be a simple fix. I guess it could also be a top end issue, so I'll check valve clearances too. This is the first time I've actually considered doing any maintenance whatsoever to the engine because up until now it's always been perfectly reliable. Never more than 3 or 4 pulls to fire it up when cold. I suppose it can't be blamed for playing up after 20 years of complete neglect. I estimate it would have done about 500 hours of mowing since I rescued it from the tip.
One of the small kindnesses I did for the motor was to always put a splash of Castrol R racing oil in the fuel as an upper cylinder lube. Although I confess that my main motivation for doing so was not so much for the health of the mower, but because I like the smell. It would transport me back to my old motorcycle racing days over 40 years ago. Imagining myself chasing the likes of Malcolm Campbell around the race track makes a pleasant distraction from mowing the grass.
Thanks again for the replies.
Cheers,
Cam
