Hi,
Have an older, but very clean Snapper (McDonough) with a small (3.5) vertical shaft Briggs on it. Starts great cold, but will not restart when hot. I checked for spark when hot and it seems fine, nailed me good. Anybody have any thoughts?
Presumably its not getting fuel then, but only when hot. Vapour lock?
NT
Mixture too rich? Choke stuck on? Air filter partially blocked?
Might be permanently choked..is it smokey?
No idea what you are talking about, but if it was a bike and had spark plugs I'd say the plugs are overheating and you need to go to the next number in the 'cold' direction - whether this be a bigger or smaller number depending on the make of plug. I used quite often to carry two or three grades of plug for different operating conditions: a plug designed to run cool in a hot engine tending to get clogged up in a cold one and so on.
S
My first thought, too. My two (larger) B+S ones have a heat-shield between the carb and block, and another one partially around the silencer (which sits close to the carb) - plus the engine cowling is designed to direct airflow from the vaned flywheel down around the head and exhaust port. If any of those are missing it'll likely upset the mixture.
If it's old, might also be the fuel line internally collapsing when hot.
If it has electric start, the starter might be failing and not turning it over fast enough when hot, too (I've got one that went that way, but running it from a car battery rather than the supplied battery "fixes" it).
cheers
Jules
briggies are very low performance engines. Not plug critical at all.
I'd say stuck choke, or just possibly worn piston/cylinder.
Clogged air filter is a possible too.
In general a good strip down and clean and freeing up of all bits and pieces restore them to health.
Very occasionally they get bad at (cold) starting and need valves reseating.
I've never seen one worn out completely to needing a new piston/cylinder though.
Unlikely on the 3.5.bhp unit. I have one in a Hayer rotary. Good smart pull usually sorts it. But there's a governor on it and its quite delicate..lots of springs and stuff.
Normally the choke is 'push past' full throttle. Sometimes that is maladjusted. Mien came bacj from service with what after a year of frustrated poor COLD staring, broke the pull cord, turned out to be a choke that never came ON. Its equally possible to get a choke that never goes off.
Hot starting on full choke is impossible. But normally it will run very rich and splutter if the choke is on full time.
So colour photo of plug removed after allowing to cool from its turned off while hot state, would help (If OP hasn't checked could even be as simple as loose plug or leaky washer, or crossed threaded plug.).
S
The governors on mine are both pretty worn (the in-sump bracket in particular, which means there's a lot of slop in the system), but it doesn't seem to affect them as much as I would have expected - at least not on the larger engines I have (10 and 11HP, the smaller ones might be different). They hunt a little when unloaded, but it doesn't seem to cause problems with starting or running under load.
Yeah, I can see that happening if the setup's anything like mine; the choke linkage design seems prone to binding due to the mechanism and angles involved, and the throttle cable mounting position has to be just right to enable the choke plate and throttle plate to perform correctly.
cheers
Jules
Classic symptom of an over-rich fuel mixture. Any engine that's starts fine from cold won't have anything wrong with the ignition because a fault there would make it much harder to start from cold than hot.
As has already been suggested either choke stuck on or wrongly adjusted, filthy air cleaner or carb flooding (punctured or misadjusted float) or other internal carb fault such as worn jets or a broken diaphragm if it has one. Should be easy enough to work through those.
Dave Baker Puma Race Engines
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