Hi Bruce, thanks for answering so quickly.

When the mower started playing up last weekend I thought it might be the carb, as it would take a few pulls to start (unusual) and then run up to revs then die, as if the fuel wasnt getting through.

I took the tank assembly off the top to get at the carb. I didnt touch anything up here at this point.

I took the white cover off the carb by undoing the brass screw. As I eased it out the float and plastic 'needle' fell out. The needle had worn on the end so I thought I had my problem solved. The o-ring was a bit dodgy so I decided to check the rest of the carb out while I was there to save two trips to the local parts place. I popped the end cap off the carb and took the spring out. I eased the thin metal diaphram cover off the white plastic spindle. The diaphram itself looked good. I gently folded the diaphram back far enough to check as much as I could see in the carb itself. I noticed the rear rubber block, which held the ignition cut-off wires, was perished and the wires were quite loose. I decided to replace it as well.

I put it all back together with the new needle and rubber bits. I replaced the spark plug. I fired it up, which took a bit of pulling, and it ran, but wouldnt idle. Below half throttle it would die. At full throttle though it ran just like it always did, with the governer working OK. I did the lawns and put it back in the garage to worry about it this weekend instead.

This morning I took off the tank assembly, having pulled out the fuel tube from the carb.

I removed the plastic dirt shroud which just lifted away.

Once that was clear, I checked around the crankcase and could see a good 30mm part of the o-ring peeking out from between the starter housing and crankcase - it had obviously been crimped in like that at the factory. It had sealed OK, as the mower ran flawlessly for four years from new, but as it was now perished and had cracks in it, the crankcase joint was leaking.

I undid the three bolts holding the starter housing to the crankcase and took it off. The o-ring fell out in bits. Another trip to the parts guy and I had a new o-ring. I ran some oil around it and fitted the ring to the starter-housing and reassembled it, twisting it slightly from side to side to bed the o-ring in properly. I also opened the carb again and checked everything was OK in there. This time I pulled off the rubber tube from the small 'ufo' shaped thing for clearance (Im not sure what it is called but which I assume is part of the governer). Everything else looked fine.

I reassembled everything and turned on the fuel tap; immediately petrol began leaking from the priming bulb. I opened the carb again and made sure the needle and float were OK - I must have bumped it offline when assembling it as this time it worked OK. I made sure all hoses were back where they came from - the fuel one to the carb and the other one to the 'ufo'. The mower started with two pulls, which made me happy. But, when I throttled up, it just kept going, and I throttled back and let the mower warm up. It now idles beautifully and at about half-throttle it gives me the nice steady 'put put put' that I had before, but long grass just bogged it down - no governer at work. I cant see what I have upset as far as the thing goes, but I also dont know how the governer works on it anyway, so no surprise there.

Sorry for the long post, but I hope this is accurate enough for the pros to make a diagnosis.

Cheers from accross the ditch.

Dave.