It sounds to me like the carb might need a good degunking.
Probably plugged or partially plugged jet/s. Try screwing the
needle valves in (gently!) and back out a few time,s then put
back to where they were and see if it helps. If not, perhaps
something's plugged.
You did check for a waterlogged/plugged fuel filter, right?
Fuel's getting TO the carb?

HTH,

PopS


wrote in message
oups.com...
: Hello everyone! I have a Briggs and Stratton 3.5hp engine
fitted to a
: Hayter rotary mower from the mid 1970s. The Model number is
92982 and
: the Type number is 1640-01. It's a 4 cycle, single cylinder,
L-head,
: air-cooled engine for information.
: The problem is I have had it sitting idle for 5 years as the
starter
: rewind spring broke and lack of time prevented getting it
sorted
: sooner. Last week I bought a new spring, rope, (approved
Champion/B&S)
: spark plug and air filter foam element (old one was
disintegrating,
: saturated new one with oil and squeezed excess out), filled the
sump
: with fresh oil and put in half a tank of fresh 95RON unleaded.
: So far, so good. But pulling the rope and some carburetor
needle valve
: tweeking got the engine to start eventually, burning off the
oil I had
: put in throught the spark plug hole. It then splutters and pops
(rich
: mixture burning within the exhaust?) The spark plug has looks
like it's
: not running lean (fuel/oil on it). It then cuts out (maximum of
about
: 15 seconds after starting). Then you can restart straight away.
Any
: ideas as to the adjustments I need to do (I have found I can
start it
: and get it to idle very slowly with the throttle lever set to
minimum).
: Do I need to play with the idle adjustment screw? Is there the
: possibility that the carburetor needs new parts too? I've heard
B&S do
: carburetor kits - how much would I be looking at (UK Pounds)
and what
: parts do they contain - anyone ever used one?
: I know this is a long posting, but i'm not too hot on my
knowledge of
: getting carbs to work perfectly for a smooth idle.
: Thanks in advance. (This email address is invalid because of
spammers
: so reply on here).
: