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...I need your assistance.
I am not very mechanically minded at all. I know next to nothing about engines. But, having lived in Yorkshire for nearly twenty years, I am tight. I want to fix my petrol lawnmower (Briggs and Stratton engine )myself - it isn't actually broken but doesn't sound too healthy, I think its in need of some TLC before it does give up the ghost. There are a lot of youtube videos on how to repair your lawnmower but I think I need to diagnose the problem first.
Basically, it starts fine, but then when its running and I'm cutting the lawn, every 30 seconds or so the engine slows down to a putt-putt-putt, as if it's about to cut out/run out of fuel, then it goes back to normal - it seems to cough out a bit of black smoke when it does this, which it doesn't do the rest of the time.
I'm thinking (but really I'm clueless) that some new oil, a clean of the oil and air filters ( or replacement?) could help...I'm guessing it has nothing to do with the spark plug(s)? ( I don't know how many it's got). I've just watched a youtube clip of cleaning the carburettor, could it be that?
Please help.
Sounds like a fuelling problem, cleaning the carb will probably fix it.
Checking the spark plugs will tell you if it's running rich (too much fuel = sooty spark plug) or lean (too little fuel = browned spark plug)
Changing the plugs, oil and oil filter won't hurt either
You could also check the points, to make sure that it's sparking when it's supposed to.
Briggs and stratton will probably have downloadable manuals for your mower, which should show you how to do the above.
From your description, it sounds like a dirty/clogged air filter. Take out, wash, re-oil with anything you have to hand and wring out so it is nearly dry but tacky.
The other likely culprit would be a split carb gasket/diaphragm, fairly common. You can either buy these individually, or as a kit with a few other service items.
Good thing about Briggs & Stratton, after sales support and spares availably is superb.
Changing the fuel filter won't do any harm either(if it has one fitted).
Is it two or four stroke?
change the fuel filter and the others and you have gone some way to solving the problem. Drain and clean out fuel tank, fresh fuel and oil.
Decent priced service kits/spares from here
http://www.gardenhirespares.co.uk/
HTH
Oh, just remembered, it could also be a broken/missing spring on the throttle linkage/governor.
So, if I were you, I'd do (in this order):
Clean and re-oil air filter (it needs doing anyway)
Check all springs are intact and attached correctly (look for photos online showing where they go)
And finally, rebuild the carb
Cheers for the tips guys
The following is from B and S's help pages:
Troubleshooting A Fuel Supply Problem
Remove the air cleaner and inspect the choke plate mounted on a shaft at the opening of the carburetor's throat. Check that the choke plate closes easily and completely.
Shaft, choke, throat? Eh?
Is it two or four stroke?
I put normal unleaded in it, does that mean it's a four stroke?? I am embarrassingly without any idea whatsoever. I think I need to put special oil in, which now I think means it's probably two stroke??
😳
Followed your link mulacs, lawnmower parts are MUCH cheaper than bike parts!! Some bits look quite bling too...