4-stroke engine 'hunting'.

Biggus_Dickus

My son has a 4-stroke self propelled ‘Challenge’ mower;...the engine always starts first time but it ‘hunts’ continuously (and annoyingly) when in use.

I've checked the usual suspects, ...air filter...spark plug/cabling...fuel etc, but nothing obvious.

The Challenge website suggests this...”it is most likely that the jets are blocked inside your carburettor... you can either try cleaning it yourself (purchase a 'carburettor cleaning kit'), or taking it to a local garden machinery centre for a service.”

Is it a diy job?... or best left to a service centre? ...I’m not too bad on the ol’spanners , but these days not if it’s very complex, over fiddly and time consuming.

 

lemondrops69

4 stroke mower engines are straight forward. Good old you tube might have a video to help. Wait till your sons out before you have a go at it, if you mess it up you can deny all knowledge 

Grumpy_chap

lemondrops69 said:

4 stroke mower engines are straight forward. Good old you tube might have a video to help.

Have you been possessed by Fred?
Maybe someone here can recommend a good poltergeist.😆

lemondrops69

Yes, always avoid the dealer and always use you tube. 

BOWFER

Have you checked for an air leak along the intake?
Check where the air filter joins onto the carb, and where the carb joins onto the manifold.

bob_a_builder

Biggus_Dickus said:

Is it a diy job?... or best left to a service centre? ...I’m not too bad on the ol’spanners , but these days not if it’s very complex, over fiddly and time consuming.

Certainly on the usual Briggs and Stratton type engine most often used in mowers - 
Its neither complex, over fiddley or time consuming
Its a very simple job to take off and clean the carb - should be no 'challenge' at all, if you know one end of spanner from the next  - no more than 20 mins 

But seems yours might have a Chinese engine ( possibly just a copy of a B&S) 

Some model specific assistance here on the issue, possibly
https://www.diynot.com/diy/threads/lawn-mower-hunting-surging.480356/

AdrianC

You should probably consider running a good solvent through the fuel system.
One of the best and cheapest solvents is... petrol.

Challenge is an Argos own-brand. First step is finding out who manufactured the actual motor on it...

Ganga

If its a Briggs and Stratton engine the pick up pipe on the carb into the petrol tank has a filter on the bottom which can clog up ,also might just need the mixture screw on the side adjusting.

daveyjp

Have a look at Mustie1 videos on youtube.  He strips down loads of 2 and four stroke engines and carbs.

EssexExile

Is there a breather hole in the petrol cap? If not, make one.

Biggus_Dickus

bob_a_builder said:

Biggus_Dickus said:

Is it a diy job?... or best left to a service centre? ...I’m not too bad on the ol’spanners , but these days not if it’s very complex, over fiddly and time consuming.

Certainly on the usual Briggs and Stratton type engine most often used in mowers - 
Its neither complex, over fiddley or time consuming
Its a very simple job to take off and clean the carb - should be no 'challenge' at all, if you know one end of spanner from the next  - no more than 20 mins 

But seems yours might have a Chinese engine ( possibly just a copy of a B&S) 

Some model specific assistance here on the issue, possibly
https://www.diynot.com/diy/threads/lawn-mower-hunting-surging.480356/

Thanks for the DIYnot link;...certainly some food for thought in that thread. 

It’s a Challenge SE475 engine. If required, a new carburettor assembly is £19.99 which doesn’t seem too bad.

The mower is 4 years and well used,...I’ll probably give it a good tinkering but if it means spending any significant cash/time to repair we’ll probably just replace it,...or alternatively  put up with the ‘hunting’ until it finally gives up the ghost. It still cuts really well though.

Thanks to all for the replies.