Running a motor mower on unleaded petrol

[singalong]

I have a petrol driven motor mower that runs on "regular" grade petrol.

Without me knowing the last twice when my wife has had the mower petrol can filled she has used "unleaded" (This over two years or more)
Just recently my mower had become more and more difficult to start and today when I finally got it started it would only run with the carburettor setting continually in the "start" position and eventually gave up the ghost and stopped.

This all came to light over dinner this evening so my question is:

Have I done any permenant damage to the motor using unleaded in lieu of regular?
Is there an additive that I can add to the non leaded petrol to turn it into "regular"
Any useful comment appreciated.

 

[JohnD]

unleaded is OK. It just wants servicing.

Quite possibly the carb jets are clogged with old dirt and sediment from the tank (often happens with motors that are left unused all winter.e.g. plaything motorcycles).

Why have you decided to blame the grade of petrol?

 

[singalong]

I blamed the petrol because the manual stated "regular" petrol and I assumed "non leaded" would be a problem.

 

[JohnD]

Unleaded has been the norm for what? ten years? And longer in Japan. Is the engine older than that? I'd say Unleaded was "Regular". Motor mowers are quite undemanding, if it wanted a high-octane I'm sure it would say.

Is it a 4-stroke?

 

[singalong]

Yes it is a 4 stroke and it is over ten years old

 

[singalong]

It fact I purchased it on the 10/04/93

 

[JohnD]

Due a service then. Maybe the valve seats are worn. Is it Briggs & Stratton, or Honda, or what? there might be info on the engine maker's website.

You can get an lead-subsititute additive, rather expensive. Almost all the garages that used to sell LRP seem to have stopped now. the old car clubs usually say, run the engine on unleaded, and if the valve seats erode, have new hard inserts put in when it gets bad enough to be troublesome.

 

[tonysab]

I have recently been thinking the same thing - I have a Mountfield Mirage 4 stroke Briggs & Stratton that I acquired from a friend - with the recent lack of leaded petrol available I was wondering if I can use unleaded - someone said I might need to change the spark plug? Should I give it a go with unleaded, not sure what the alternative is to be honest?

 

[JohnD]

Have a look on the Briggs & Stratton website, and let us know

 

[johnf]

Tonysab,
I've got a Mountfield M4PD with a 4-stroke Tecumseh engine. I acquired it 2nd hand from my father-in-law in 1987. I last had it professionally serviced in 1988. Since then, I've changed the oil about every 2 years, and the spark plug 2 or 3 times in total. I've always used unleaded, though occasionally, when I've run out while mowing the grass, I top up with some 2-stroke mixture from my boat outboard can.
These engines will run on anything - you could p*ss in the tank and they'd still go.