Lawn mower help

Hello all. I have an older Mountfield mower. I could do with help with. It hunts all the time. Reving back and forth. I've stripped it and Cleaned the carbs once.
Does anyone have knowledge of them.??

 

Morning @Portisgrass
I have had similar problems some years ago, after I had cleaned the carb out and the chap in the repair shop told me that it was because the diaphragm had stretched and they never go back properly; so he always replaced the diaphragm. Since then I have always replaced the diaphragm every time I have had the carb off the fuel tank and had no further issues. I think the diaphragm stretches over time and use anyway and I am planning on fitting a new one over the winter as part of the service.
I am assuming you have a Briggs and Stratton engine though.
Either of these sites might help https://www.mowermagic.co.uk/acatalog/briggs-stratton-spare-parts.html and http://www.briggsbits.co.uk/acatalog/index.html

 

As sayed above the diaphragm in the carb or may be still some dirt in there or it could be the petrol cap there's a air hole that may be blocked not letting air in as the petrol goes down having a vacum so not getting it full fuel

 

Most likely duff diaphragm. A good dose of Seafoam wouldnt hurt.

 

Had a smiliar issue recently, muck in the carb, although Mine's a Hayter, not a Mountfield. Was running like a bag of nails until the carb was stripped and cleaned out.

It could well be the diaphram as @NigelJ and @WeeTam suggested.

My only advice would be always blow any dust, shrivelled grass clippings from your fuel nossle each time you refuel as they always seem to find a way to pick up rubbish. Fitting an inline filter into the fuel hose will seriously reduce any debris finding its way into the carb, therefore less diaphram replacements.

A lot of mowers aren't fitted with fuel filters as standard and small ones are obtainable from most motorspares shops or lawnmower service centres for a couple of quid or less. It just means a bit of jiggery-pokery with the fuel hose and cutting out a section to the exact length the filter occupies, assuming that's possible as sometimes the petrol on/off tap can get in the way.

 

Thanks NIgelJ
No,
Is a Honda GV100 engine mountfield lazer It starts and runs but I think you guys are perhaps correct re the diaphragm. I will try this and let you know. If I can find one. Dam machine is old as the hills, can bring my self to throw it.

 

Hopefully you'll get it fixed.

A customer who moved away had an antigue Mountfield M5 (or M3... anyway it had a steel rear roller) that she instisted on being used on her lawn. It was self-propelled and was like being towed by a snail but it did the job, and the lawn always looked magnificently striped when cut - but it would use nearly a litre of fuel in just over half an hour of cutting. My Hayter would have done it almost twice as fast and used a quarter of the fuel.

Sometimes you have to cut your losses and some newer machines can be rather expensive but in the long term, the costs of maintenance and fuel efficiency may outweigh the costs of keeping an old beast alive, especially if you have a large lawn. Jusy talking from experience.