Briggs and Stratton

[James2]

Hi,

I have a problem with my Stiga lawn mower,

the Briggs and Stratton engine will not run.

Recently the engine spluttered and stalled, upon investigation, I found the oil sump full of petrol. I have dismantled and cleaned all parts of the carbereta, checking the needle and float , drained out the contaminated oil and refilled with fresh petrol.

When I restarted the mower, the engine ran for about ten minutes and then stalled, checking the oil sump again, FULL OF PETROL.

Can anyone advise me?

Regards James2

[Théière]

After cleaning the carburetor did you check the float poperly shut off against the needle valve, was there a fine ring around the viton seal on the top of the needle, any wear will allow fuel to continue to flow.

 

 

[Gluestick]

Usually this phenomenon is caused by one of two faults:

A Control Diaphragm in the carburettor is perforated:, or;

The main Diaphragm in the fuel pump is split.

By the quantity of petrol apparent in the sump after only ten minutes running, I would check the fuel pump.

If your mower uses a Gravity Feed system only, then the problem lies in the carb.

It is strange that the engine would run for ten minutes, however, if so much petrol was simply washing into the cylinder: i.e. sufficient to soak past the piston and rings and into the sump!

I would thus opt for a problem with the Vacuum Operated fuel pump.

 

[James2]

Hi ,

The engine is gravity fed fuel, when I checked the needle in the carbereta all seemed OK, a very small orange coloured seal at the tip of the needle, I assume is the `viton seal ` appeared to be in good condition, however what is the best way to check the seal is not leaking?

All advice greatly appreciated.

James2

[f1steveuk]

I take it the float has no petrol in it? It's obvious the flow rate is way to high and doesn't sut off, so it has to be the float and/or the needle valve. Can you Google the engine/carb, and if it gives an exploded (not the best choice of words where petrol is concerned!!) post a link, and we can have a look.

[Théière]

Steve, they are very basic carbs, similar to an SU float and needle valve arrangement. Very concerned as a friend blew up two Briggs and strattons (pistons split vertically in two) and I have a feeling that the same fate may await if the oil is being washed out of the bore.

 

[James2]

Hi,

Thanks for the diagram, I take it I need to dismantle the carbereta again and perhaps replace the needle and valve? as it looks as though this is how petrol is getting in the oil sump.

Regards James2

[f1steveuk]

Normally it's the float that shuts off the fuel flow, unless the jets are held open by dirt in between the needle and it's seat. I'd have thought a strip down on a CLEAN sheet of pepper, and a good clean should really sort it. Petrol flow through a carb' can wear the inside quite a lot, but it would take a while in a little carb like that I'd have thought. Reminds of the time I used an air line to clean an Escort carb', and shot a valve several hundred feet!!!

[James2]

Hi

Thanks for your help, will procede to dismantle the carbereta and give it a thorough clean, checking for any obvious dirt or anything that may have caused the leak.

Will let you know how I get on.

Regards James2

[Théière]

James don't forget to check the float floats, a pin hole would mean it would stay submerged and also not shut off the fuel.

Another point to look at is the spindle that passes through the float, any tightness will also prevent shut off.

Good luck