Lawnmower Engine Maintainance

[stevelup]

Hi

We inherited a petrol lawnmower with the house we recently bought. It appears to have been sat for approximately six months and was not 'decommissioned' properly before being left.

I simply can't get it to run properly. The fastest it goes is a rough idle and it stalls whenever you hit any thick grass.

It is a generic Italian manufactured machine - the same as which is seen in most of the DIY sheds under various names. It has a 150cc Briggs and Stratton engine.

The spark plug is clean and correctly gapped. The armature is correctly gapped and the spark is healthy and reliable. The throttle plate moves freely in response to feedback from the governor. I've replaced the oil and it has fresh fuel in it. There are no other adjustments (relating to the fuel mixture etc.). The compression seems fine - if you spin the flywheel backwards, it bounces back with a healthy snap.

I don't know what else to try? Does anyone have any advice?

Thanks,

Steve

[TMC]

Diaphragm in carb

about 20 mins to do £4.00 for diaphragm

Google Briggs and Stratton lots of exploded diagrams

Tony

[Alan]

In message , stevelup wrote

Remove the carburettor/petrol tank assembly - if it was anything like mine there will be one difficult to see screw at the back of the carburettor.

Remove the carburettor. from the tank and I bet the fuel filter(s) will completely blocked with c**p - probably an emulsified petrol/rust compound of some sort. I found that cotton buds and rising with petrol did the trick (the crud sinks to the bottom of a bucket so you can recycle the petrol when cleaning). There was a lot of crud in the petrol tank.

Usual obvious warnings about safety should be observed. For comfort you will need to work somewhere warm - the front room in front of the open fire is ideal :)

[Nick]

Another possibility is that the tiny fuel passages in the block of the carb body have been "furred up" with residues from evaporating petrol which in turn reduces the flow of fuel - still seems to run ok at low power demand (fuel flow) but will not pass enough fuel for higher demands, mixture goes weak and the engine cuts.

This can be attacked wth carb cleaner - immerse parts in it and try to flush fuel through the tiny passages. - also put cleaner in the fuel tank and let it run through.

Nick

[Andrew Gabriel]

I agree with all the points posted so far. Also, check the air filter. They probably vary in design. Mine was a piece of foam sponge which you wetted with clean engine oil and wrung out to ensure even coating but no excess. To clean it, you washed it in petrol, and dried out by wringing and then squashing in kitchen roll to get most of it out. Then wet with clean engine oil and wrung out again.

[stevelup]

Hi

Thanks everyone for the tips. I'll attack it some more tomorrow.

Cheers,

Steve

[Tim Lamb]

In message , Nick writes

My local *repair shop* (Taylors Tools, Kings Langley) offers an ultrasonic bath for de-gumming carbs. Around a tenner and while you wait if you phone first so they can switch on the heater.

regards

[Nick]

I think Aldi or Lidl are selling an Ultrasonic bath now or soon.. - might be worth a punt ..

Nick

[stevelup]

Hi

It was indeed the diaphragm - its working perfectly now.

Many thanks,

Steve