On Sat, 23 May 2009 16:30:46 -0700 (PDT), muzician21 wrote:

Have a B&S on a 70's era Snapper 21" pusher with an aluminum deck. I
believe the engine is probably 10 years newer than the rest of the
mower.

Maybe 10 years ago I took it to a repair shop who installed a solid
state unit to replace the points. Even with the solid state ignition
it was never one-pull start, but as I recall it usually started with
probably 3 - 5 pulls. Now it takes probably 20 pulls or more and
monkeying with the throttle. Once it fires it runs like a clock, runs
up and down the speed range fine. It's also easier to re-start once
it's been running - though still not one pull. Doesn't seem to use an
inordinate amount of oil, no discernible smoke out the exhaust. It
gets what I'd call moderate use. I'm in central Florida so it gets run
bi-weekly or so during the rainy months, not at all during the months
of what passes for a winter down here.

I'm mechanically inclined but not well-versed on the theory of this
kind of engine. I've had it broken down far enough to remove and flush
the gas tank, change the points when it had points, replace the pull
rope. I've change the spark plug of course. I know it should start
much easier than it does. Any suggestions where to look, what to
tweak? There isn't that much to it from what I can see, so it
shouldn't be that difficult. I believe this mower has a lot of life
left in it.

Thanks for all input.

It certainly seems that there's a fuel problem when cold, since you say the
engine runs fine once started.

A couple of suggestions, with apologies if they're not relevant due to the
layout of your particular engine:-

1) Remove the air cleaner and see if you can look into the carburettor's
air intake pipe.
Normally there will be a spring-loaded butterfly valve, which is closed
when the throttle is in the "start" position. If there's any obstruction
preventing this butterfly valve plate from closing properly it can allow
too much air to enter in the start position, so the start mixture isn't
rich enough.

2) If the carburettor has a priming bulb (which you push to prime the
engine), give it two or three pushes while you're looking into the intake
pipe, and confirm that raw fuel is being squirted in there.

My mower starts first pull, but only since I realised that it takes a
little time for the raw fuel squirted in by the primer bulb, to evaporate.

These days I normally give the bulb four pushes, take the cap off the gas
tank, and then fill the tank from my fuel can. By the time I've done this
and replaced the cap, the raw fuel has mostly evaporated, and the engine
draws in vapour instead of liquid fuel, to start on the first pull.

Cheers,
John S

(follow-up set to rec.autos.tech, where I saw your post)