Any petrol powered lawn mower gurus?

[Alucidnation]

Morning all.

I have an Alko 42br Briggs & Stratton powered lawn mower.

A few days ago, after starting it (used it just before last weekend and it was fine) the engine was surging and hunting and would would not settle.

After a quick bit of googling i deduced that the carb gaskets could be worn so rather than purchase just the gaskets, i found a complete carb with gaskets etc for £19 so i fitted that thinking it would solve the issue but alas not!!

So, after another bit of investigation, someone mentioned that replacing the govenor and idle springs can cure it.

I must admit, the ones on my mower at the moment are quite slack but i wasn't sure if they should be tighter?

Or should i be looking at other things (that are simple to replace ).

Any help much appreciated, as i now cannot see the dog when i let it out into the back garden/field.


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[Philemon]

If yours is the carburettor with the diaphragm, then the likely cause is dirt/grass blocking one of the jet holes, or the tang at the front of the linkage being bent in towards the engine. This is usually caused by bumping the mower into bushes when mowing forwards.

If you have replaced the diaphragm already then you know how to take it all apart. Do it again and make sure that you clean the tank & carb out and install the diaphragm and gasket in the right order. Don't get carb cleaner on the diaphragm tho since this will ruin it.

Lots of videos on YouTube. Donyboy73 is a great small engine doctor.

[jeff m2]

Surging could be caused by a weak spring on the Governor arm.
The actual governor is usually inside the crankcase, I don't think you want to change that

Set the gov adjustment by moving the arm as far as it will go from its rest position, then move main butterfly to full open, tighten screw.
There are usually a choice of holes for hooking up the spring, choose one that "takes up the slack" initially.
If needed , move it into the next hole that increases the spring tension.

General info, not model specific.

[ARHarh]

Happened to me some years ago, after stripping the carb and finding no faults it was no different. after filling with fresh fuel it worked fine for a while then the problem returned. It was the breather in the fuel cap blocked.

[Alucidnation]

Thanks everyone for your help.

I have checked all suggestions and everything looked ok so I bought a couple of springs and replaced those and the hunting has been cured (I think!)

No adjustment can be done on the carb or governor and breather holes on the fuel cap and gasket all clear.

Trouble now is it just runs as rough as hell.

Took the carb off again to give it another clean and found the new diaphragm gasket has a tiny spilt in it around the part where the spring sits.

So, gasket and diaphragm ordered and so ill try that!

[jeff m2]

Once you put in the new carb kit don't use carb or fuel injector cleaners the rubber and fibre bits don't like it.
Also if you use ethanol petrol with carbs make sure you use ethanol stabaliser in the winter not the original stabaliser, more important for classic cars, but holds true for mowers etc.

There are issues with ethanol and carbs.

[8-P]

I had an issue with mine recently. Wouldnt start, followed the video below, seemed to be a blocked jet I think, fuel wasnt getting to the engine.

Found a good source on ebay for bits:

http://stores.ebay.co.uk/Spares-for-all-seasons/_i...

Dont forget you can adjust the carb, there is a screw (idle screw?)

5 mins on here

https://www.youtube.com/watch?v=I-dkqIdv9GE

[Alucidnation]

Thanks for the links!

Unfortunately my carb is the newer plastic non adjustable type.

Hopefully the new gaskets will be here in the next day or so, so i am hoping that will sort it!

I have also discovered that there is another breather fitted to the engine, so that might be next if the gaskets don't help.

[8-P]

Also just found this, they even have the carb for my mower - only place Ive found it too.

https://www.briggsbits.co.uk/

[Alucidnation]

OK, success at last.

Turns out it was the diaphragm that came with the new carb that was casing the issue, as it had a tiny split in it.

Just replaced that and it now runs better than ever!

Thanks again everyone!

[8-P]

Alucidnation said:

OK, success at last.

Turns out it was the diaphragm that came with the new carb that was casing the issue, as it had a tiny split in it.

Just replaced that and it now runs better than ever!

Thanks again everyone!

Ive seen a few reports of diaphragms causing issues. Amazing really when all it really is is a small seal between the carb and the tank right? I didnt totally remove mine for fear of damaging it. Probably like yourself, having mucked around with the carb area now Im pretty confident I can keep this mower going indefinitely!