mower running badly

We have a small self-propelled 4-stroke petrol lawn-mower that has run well in the five years that we've had it, despite having minimal maintenance. :o When I last used it, a couple of weks ago, it ran really badly, hardly pulled itself along and I struggled to cut the grass.

I checked the plug - ok. I took off the air filter and cleaned the sponge, took off the panels surrounding the carb and checked it for blockages or muck but found none. I was a bit baffled as I could see no adjustment screws so reassembled it to no avail, it still runs lumpily.

It's got a pretty standard Briggs and Stratton engine, has anyone got any suggestions to make it run properly?

Yours hopefully, Chris

 

Thanks John. I did give the filter a bit of a clean and scraped around the plug to get the clag out but perhaps I ought to invest in a new one. It does seem strange that it hasn't got an idler adjusment screw because when I manually open the throttle butterfly it revs up icely. Curious.

Chris

 

Mine just chugs at the moment. The plug is clean and the gap is correct, the air filter is clean. I cannot find a way into the carb. (if it has one!) to see if the jets are blocked. There is enough petrol in it too and the underside is not clogged with grass. What next?

 

Sorry you've got problems Palustris. I haven't used mine for a few weeks but the grass has grown a tiny bit so I'll be getting it out in a day or two. I hope it goes okay. Otherwise, anyone else got any ideas for our mowers?

Chris

 

Whatr is really annoying is that the manual does not mention the engine 'chugging' only not running at all and there is no blow up picture of the engine in it either, as there was in our old Honda machine. I cannot use the old mower as a. the wheels wore out and no one has new ones and b. There is a bees nest underneath it which I do not want to disturb.

 

Oh dear! Mustn't disturb the bees! I'm wondering if the timing has slipped. I'm going to search the interweb and see if I can find out how to do it. I'll let you know if I have any luck.

Chris

 

The words "no user serviceable parts" seem to occur more frequently in the instruction books with anything mechanical we buy.

 

As it`s self drive, could the clutch cable need adjusting?:thumb:

 

Donn't see how that would affect the engine just chugging rather than running when the drive is not engaged until one pulls the other lever.

 

With any internal combustion engine that stops working unless any settings get altered it can only be either, fuel, spark or air.

 

Are you sure that the choke is off, if it's not fully off then that can make it run badly. Too rich mixture.

 

These machines do not have a choke as such.

 

That's right, they have a plunger to prime the carb, prior to starting. My research has thrown up a couple of possible things. If the flywheel key is damaged it will cause vibration and hence, poor running, but what is interesting is that the cutting blade acts as a flywheel and if it is bent or damaged it can cause the engine to run badly. Palustris, have a look at this: http://www.westongm.eclipse.co.uk/Diagnosis.html

Chris

 

Cheers. As far as I can tell, the cutting blade is as straight as it should be. I am waiting for my mechanic son to be bothered to answer his Emails to see what he can suggest. I may have to bite the bullet and drive the machine (in the back of the car, not the actual machine itself,silly) over to him. Cut the top lawn with the electric mower just, grief the pain in my back is not something I wish to have.