Petrol Lawn Mower running rich

[Toilet Duck]

Hello,

My petrol Lawn mower is running rich, its drinking twice the amount of petrol it used to. I recently changed the oil/air filter/spark plug as it was sounding rough. Changing all this has not made any difference. The old plug was black/sooty when I removed it. I checked the new one today and its black as the ace of spades allready. I pulled the air filter off again to have a look around the carburettor area but I can't see any magic screw or something else I can fiddle with. There are some springs that seem to regulate some piece of metal that fluctuates when the motor is running. Can I weaken the mixture myself or is it just knackered? Chhers in advance for any help!











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[trev540]

Had the same problem the other year with what looks like the same mower. Tried new plug and tinkering then gave up and took it to a repair man and he said its the diaphragm. £30 and a day later all was well.

[Trevelyan]

I serviced one of these carbs on my mower this year. As far as I can remember there's no adjustment on them. It might be worth trying to service it yourself to check that none of the jets or passages are blocked. Mine looked immaculate but the mower was running very roughly. After a stripdown and a liberal dose of carb cleaner it's now running perfectly.

I found some videos on youtube showing how to do it. I think this was the one I followed in the end.

http://www.youtube.com/watch?v=Gg4OWXW520k

The carbs are pretty basic lumps of plastic - it's possible that you'll be able to pick up a new one for the same cost as trying to get the old one serviced. I didn't research any prices though.

[rovermorris999]

It might just want a decoke, have a look in the plug hole with a torch. I had a similar problem with a B&S engine, you could see the crud.

[Toilet Duck]

Cheers for the replies chaps, maybe there is hope yet! I'll have a look inside the spark plug hole (how do I de-coke it if neccessary?) and check out the youtube guides. I'll also investigate the diaphram

Many thanks

[rovermorris999]

To properly decoke it's cylinder head off I'm afraid. You may get away with filling the bore with Redex and leaving to soak for a while. Follow the directions on the bottle but make sure you change the oil directly afterwards.

[MJG280]

trev540 said:

Had the same problem the other year with what looks like the same mower. Tried new plug and tinkering then gave up and took it to a repair man and he said its the diaphragm. £30 and a day later all was well.

What he said. Also previously I did an oil change and that gave a rich mixture as the oil was too thin. So did another oil change and ok till it started being smoky and had the diaphragm changed for also £30