Fuel advise for my Hayter Kestrel/Briggs & Stratton

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Last seen: 3 months 1 week ago
Joined: 25/05/2019 - 14:53
Fuel advise for my Hayter Kestrel/Briggs & Stratton

Hi Everyone,

I have a Hayter Kestrel Lawnmower, with a Briggs and Stratton engine.

I was a bit of a 'barn find' when I picked her up and I couldn't get her running, so she sat in my barn for a few years.

Last year I finally booked her in with the local lawnmower services place and they've given her a good service and she's now running....sort of.

I've only run her for a short while using the fuel that the shop put in her. I know she's a 4 stroke engine and thus the petrol and oil are separate...I don't need to mix them, but I don't know if she can safely run on unleaded or do I need a fuel lead replacement supplement?

She'll be running out of fuel shortly I should think and I don't want to put the wrong stuff in. I've managed to get the manual for the mower, but it doesn't tell you anything about the engine and I'm struggling to find anything anywhere that does.

The other query I have is regarding oil and cooling. After a few minutes of cutting she comes to a sudden halt (engine not mobility). The only thing I can liken it to is an over-heating engine seizing. If you try to pull the chord it's tight, but if left for a few minutes to cool down she fires up and runs again.  How is this engine cooled and could this be caused by the wrong oil?

Sorry for all the questions, but I'm struggling to find anywhere else to turn to.

Many Thanks


Last seen: 1 hour 10 min ago
Joined: 08/04/2013 - 17:02
The engine is air-cooled by

The engine is air-cooled by the fan (part of the flywheel under the starter), this blows air over the cylinder fins and cylinder head. These can get clogged with dried grass etc, but I would have expected this area to be cleaned during a service

The engine is fitted with hardened valve seats and is capable of running on lead-free petrol.

The oil in the engine should be a good quality SAE 30 grade, perhaps they filled it with SAE10w30.

Do not continue to use the mower until you have cured the possible overheating problem, it should be capable of running for hours without overheating or seizing, unless you are doing something like mowing on a slope.

wristpin's picture
Last seen: 1 hour 54 sec ago
Joined: 23/05/2012 - 22:09
Standard unleaded fuel is

Standard unleaded fuel is fine.

The engine is air cooled. Remove the blower housing - top cowling - and make sure that all the cooling find are free of debris.

Oil . A high detergent SAE30 monograde.  NOT the non detergent 30 sold by Halfords etc for classic cars.

Air cleaner. Remove the sponge - if it falls apart they can still be purchased - wash it in petrol  or hot water and detergent. Wrap in old towel and squeeze dry. Then dose with a good “ dollop” of new engine oil , work it into the sponge and then wrap in the towelling and squeeze out the surplus. When  refitting the sponge to the air cleaner case , don’t tuck it all down inside, the lid should push down on the overlap to make a seal.