Drive me mental sometimes.
Basic, simple lawnmower petrol engine. Briggs and Stratton I think.
Runs for a few seconds, maybe a minute, then stops. Will start again immediately.
I can keep it running continuously on ether.
Different spark plug, same result.
Brand new carburettor, same result.
Drained fuel, fill with fresh fuel, same result.
Run without fuel cap on, same result.
New fuel pipe, 100% not kinked, same result.
Fuel flows freely out of the float chamber.
The only slight weird history of this engine is I ran it on diesel by mistake once. That was some time ago and it was fine again after I go
rid of the diesel.-a Another time it loast all compresson when I ran it
on old fuel - that was a valve that got stuck.
WTF is wrong with it?
On 12/05/2026 19:29, Simon Wilson wrote:
Drive me mental sometimes.
Basic, simple lawnmower petrol engine. Briggs and Stratton I think.
Runs for a few seconds, maybe a minute, then stops. Will start again
immediately.
I can keep it running continuously on ether.
Different spark plug, same result.
Brand new carburettor, same result.
Drained fuel, fill with fresh fuel, same result.
Run without fuel cap on, same result.
New fuel pipe, 100% not kinked, same result.
Fuel flows freely out of the float chamber.
The only slight weird history of this engine is I ran it on diesel by
mistake once. That was some time ago and it was fine again after I go
rid of the diesel.-a Another time it loast all compresson when I ran it
on old fuel - that was a valve that got stuck.
WTF is wrong with it?
I had two B & S engined machines at 'the chateau'. One ride on mower,
one three-wheeled brush cutter.
I certainly had the blocked fuel cap vent issue on the brush cutter
once, but you have eliminated that.
Weird that it will run OK on ether, or I would be thinking spark loss
due to heating of the ignition 'winding' breaking down the insulation. I think ether doesn't need such a strong spark.
Can you get a 'softer' or fancy electrode material plug in the same
size? Or test the resistance of the winding when hot?
On 12/05/2026 19:49, Peter Fisher wrote:
On 12/05/2026 19:29, Simon Wilson wrote:
Drive me mental sometimes.
Basic, simple lawnmower petrol engine. Briggs and Stratton I think.
Runs for a few seconds, maybe a minute, then stops. Will start again
immediately.
I can keep it running continuously on ether.
Different spark plug, same result.
Brand new carburettor, same result.
Drained fuel, fill with fresh fuel, same result.
Run without fuel cap on, same result.
New fuel pipe, 100% not kinked, same result.
Fuel flows freely out of the float chamber.
The only slight weird history of this engine is I ran it on diesel by
mistake once. That was some time ago and it was fine again after I go
rid of the diesel.a Another time it loast all compresson when I ran it
on old fuel - that was a valve that got stuck.
WTF is wrong with it?
I had two B & S engined machines at 'the chateau'. One ride on mower,
one three-wheeled brush cutter.
I certainly had the blocked fuel cap vent issue on the brush cutter
once, but you have eliminated that.
Weird that it will run OK on ether, or I would be thinking spark loss
due to heating of the ignition 'winding' breaking down the insulation. I
think ether doesn't need such a strong spark.
Can you get a 'softer' or fancy electrode material plug in the same
size? Or test the resistance of the winding when hot?
Yeah the igniter thingy is just about the only thing left. Or something
with the valves again. Or an air leak (can't find one).
One thing I left out - it seemed to need choke all the time when it was running, so there's something up. Feels like an air leak now I'm
thinking about it, but no idea where.
WTF is wrong with it?
Drive me mental sometimes.
Basic, simple lawnmower petrol engine. Briggs and Stratton I think.
Runs for a few seconds, maybe a minute, then stops. Will start again immediately.
I can keep it running continuously on ether.
Different spark plug, same result.
Brand new carburettor, same result.
Drained fuel, fill with fresh fuel, same result.
Run without fuel cap on, same result.
New fuel pipe, 100% not kinked, same result.
Fuel flows freely out of the float chamber.
The only slight weird history of this engine is I ran it on diesel by mistake once. That was some time ago and it was fine again after I go
rid of the diesel. Another time it loast all compresson when I ran it
on old fuel - that was a valve that got stuck.
On 12/05/2026 19:49, Peter Fisher wrote:
On 12/05/2026 19:29, Simon Wilson wrote:
Drive me mental sometimes.
Basic, simple lawnmower petrol engine. Briggs and Stratton I think.
Runs for a few seconds, maybe a minute, then stops. Will start again
immediately.
I can keep it running continuously on ether.
Different spark plug, same result.
Brand new carburettor, same result.
Drained fuel, fill with fresh fuel, same result.
Run without fuel cap on, same result.
New fuel pipe, 100% not kinked, same result.
Fuel flows freely out of the float chamber.
The only slight weird history of this engine is I ran it on diesel by
mistake once. That was some time ago and it was fine again after I go
rid of the diesel.-a Another time it loast all compresson when I ran
it on old fuel - that was a valve that got stuck.
WTF is wrong with it?
I had two B & S engined machines at 'the chateau'. One ride on mower,
one three-wheeled brush cutter.
I certainly had the blocked fuel cap vent issue on the brush cutter
once, but you have eliminated that.
Weird that it will run OK on ether, or I would be thinking spark loss
due to heating of the ignition 'winding' breaking down the insulation.
I think ether doesn't need such a strong spark.
Can you get a 'softer' or fancy electrode material plug in the same
size? Or test the resistance of the winding when hot?
Yeah the igniter thingy is just about the only thing left. Or something
with the valves again. Or an air leak (can't find one).
One thing I left out - it seemed to need choke all the time when it was running, so there's something up. Feels like an air leak now I'm
thinking about it, but no idea where.
Drive me mental sometimes.
Basic, simple lawnmower petrol engine. Briggs and Stratton I think.
Runs for a few seconds, maybe a minute, then stops. Will start again immediately.
On 12/05/2026 21:09, Simon Wilson wrote:
On 12/05/2026 19:49, Peter Fisher wrote:
On 12/05/2026 19:29, Simon Wilson wrote:
Drive me mental sometimes.
Basic, simple lawnmower petrol engine. Briggs and Stratton I think.
Runs for a few seconds, maybe a minute, then stops. Will start again
immediately.
I can keep it running continuously on ether.
Different spark plug, same result.
Brand new carburettor, same result.
Drained fuel, fill with fresh fuel, same result.
Run without fuel cap on, same result.
New fuel pipe, 100% not kinked, same result.
Fuel flows freely out of the float chamber.
The only slight weird history of this engine is I ran it on diesel
by mistake once. That was some time ago and it was fine again after
I go rid of the diesel.-a Another time it loast all compresson when I >>>> ran it on old fuel - that was a valve that got stuck.
WTF is wrong with it?
I had two B & S engined machines at 'the chateau'. One ride on mower,
one three-wheeled brush cutter.
I certainly had the blocked fuel cap vent issue on the brush cutter
once, but you have eliminated that.
Weird that it will run OK on ether, or I would be thinking spark loss
due to heating of the ignition 'winding' breaking down the
insulation. I think ether doesn't need such a strong spark.
Can you get a 'softer' or fancy electrode material plug in the same
size? Or test the resistance of the winding when hot?
Yeah the igniter thingy is just about the only thing left. Or
something with the valves again. Or an air leak (can't find one).
One thing I left out - it seemed to need choke all the time when it
was running, so there's something up. Feels like an air leak now I'm
thinking about it, but no idea where.
Oh well, that seems significant. What is the history of the mower -
acquired from new? The new carb is presumably the correct one for that engine or just replaced to match what was already on it ? That ought to
rule out a blocked jet but not an incorrect one IYSWIM . The restarting immediately is the real mystery. A heat related ignition issue should
need it to cool down a bit first.
A new cheap pattern ignition coil/igniter might still be worth a try.
The restarting
immediately is the real mystery. A heat related ignition issue should
need it to cool down a bit first.
On 12/05/2026 19:29, Simon Wilson wrote:
Drive me mental sometimes.
Basic, simple lawnmower petrol engine. Briggs and Stratton I think.
Runs for a few seconds, maybe a minute, then stops. Will start again
immediately.
Surely
"Shit in the carbs"
HTH
:-)
Drive me mental sometimes.
Basic, simple lawnmower petrol engine. Briggs and Stratton I think.
Runs for a few seconds, maybe a minute, then stops. Will start again immediately.
I can keep it running continuously on ether.
Different spark plug, same result.
Brand new carburettor, same result.
Drained fuel, fill with fresh fuel, same result.
Run without fuel cap on, same result.
New fuel pipe, 100% not kinked, same result.
Fuel flows freely out of the float chamber.
The only slight weird history of this engine is I ran it on diesel by mistake once. That was some time ago and it was fine again after I go
rid of the diesel. Another time it loast all compresson when I ran it
on old fuel - that was a valve that got stuck.
WTF is wrong with it?
WTF is wrong with it?
IrCOm suspecting the mower issue is ignition related.
Drive me mental sometimes.
Basic, simple lawnmower petrol engine. Briggs and Stratton I think.
Runs for a few seconds, maybe a minute, then stops. Will start again immediately.
I can keep it running continuously on ether.
Different spark plug, same result.
Brand new carburettor, same result.
Drained fuel, fill with fresh fuel, same result.
Run without fuel cap on, same result.
New fuel pipe, 100% not kinked, same result.
Fuel flows freely out of the float chamber.
The only slight weird history of this engine is I ran it on diesel by mistake once. That was some time ago and it was fine again after I go
rid of the diesel.-a Another time it loast all compresson when I ran it
on old fuel - that was a valve that got stuck.
WTF is wrong with it?
On 13/05/2026 09:32, Spike wrote:
IAm suspecting the mower issue is ignition related.
But, but, it must be fuel.
<thinks> Oh, you're probably right.
One thing I left out - it seemed to need choke all the time when it was running, so there's something up. Feels like an air leak now I'm
thinking about it, but no idea where.
Simon Wilson <simowilso+newsdemon@nodamnspamn.gmail.com> wrote:
On 12/05/2026 19:49, Peter Fisher wrote:
On 12/05/2026 19:29, Simon Wilson wrote:
Drive me mental sometimes.
Basic, simple lawnmower petrol engine. Briggs and Stratton I think.
Runs for a few seconds, maybe a minute, then stops. Will start again
immediately.
I can keep it running continuously on ether.
Different spark plug, same result.
Brand new carburettor, same result.
Drained fuel, fill with fresh fuel, same result.
Run without fuel cap on, same result.
New fuel pipe, 100% not kinked, same result.
Fuel flows freely out of the float chamber.
The only slight weird history of this engine is I ran it on diesel by
mistake once. That was some time ago and it was fine again after I go
rid of the diesel.-a Another time it loast all compresson when I ran it >>>> on old fuel - that was a valve that got stuck.
WTF is wrong with it?
I had two B & S engined machines at 'the chateau'. One ride on mower,
one three-wheeled brush cutter.
I certainly had the blocked fuel cap vent issue on the brush cutter
once, but you have eliminated that.
Weird that it will run OK on ether, or I would be thinking spark loss
due to heating of the ignition 'winding' breaking down the insulation. I >>> think ether doesn't need such a strong spark.
Can you get a 'softer' or fancy electrode material plug in the same
size? Or test the resistance of the winding when hot?
Yeah the igniter thingy is just about the only thing left. Or something
with the valves again. Or an air leak (can't find one).
One thing I left out - it seemed to need choke all the time when it was
running, so there's something up. Feels like an air leak now I'm
thinking about it, but no idea where.
The fact that you can run it continuously on ether would seem to
indicate to me, that it is not a spark related issue. But Pete's point
about ether not needing such a strong spark might be true as well,
but doesn't explain why it readily starts again after stopping.
Needing the choke on all the time to run normally means it's a fuel
delivery or fuel mixture problem for sure.
There isn't that much to these things, head off, look for anything
suspect, check valve lash, check compression, spray something around
the carb isolater/gasket to check for an air leak, ???
On 12/05/2026 22:44, Mark Olson wrote:
Simon Wilson <simowilso+newsdemon@nodamnspamn.gmail.com> wrote:
On 12/05/2026 19:49, Peter Fisher wrote:
On 12/05/2026 19:29, Simon Wilson wrote:
Drive me mental sometimes.
Basic, simple lawnmower petrol engine. Briggs and Stratton I think.
Runs for a few seconds, maybe a minute, then stops. Will start again >>>>> immediately.
I can keep it running continuously on ether.
Different spark plug, same result.
Brand new carburettor, same result.
Drained fuel, fill with fresh fuel, same result.
Run without fuel cap on, same result.
New fuel pipe, 100% not kinked, same result.
Fuel flows freely out of the float chamber.
The only slight weird history of this engine is I ran it on diesel by >>>>> mistake once. That was some time ago and it was fine again after I go >>>>> rid of the diesel.-a Another time it loast all compresson when I ran it >>>>> on old fuel - that was a valve that got stuck.
WTF is wrong with it?
I had two B & S engined machines at 'the chateau'. One ride on mower,
one three-wheeled brush cutter.
I certainly had the blocked fuel cap vent issue on the brush cutter
once, but you have eliminated that.
Weird that it will run OK on ether, or I would be thinking spark loss
due to heating of the ignition 'winding' breaking down the
insulation. I
think ether doesn't need such a strong spark.
Can you get a 'softer' or fancy electrode material plug in the same
size? Or test the resistance of the winding when hot?
Yeah the igniter thingy is just about the only thing left. Or something
with the valves again. Or an air leak (can't find one).
One thing I left out - it seemed to need choke all the time when it was
running, so there's something up. Feels like an air leak now I'm
thinking about it, but no idea where.
The fact that you can run it continuously on ether would seem to
indicate to me, that it is not a spark related issue. But Pete's point
about ether not needing such a strong spark might be true as well,
but doesn't explain why it readily starts again after stopping.
Needing the choke on all the time to run normally means it's a fuel
delivery or fuel mixture problem for sure.
There isn't that much to these things, head off, look for anything
suspect, check valve lash, check compression, spray something around
the carb isolater/gasket to check for an air leak, ???
Well. New ignition/magneto thing arrived. Same result. Checked
compression, 130psi. Took the valve cover off, all seemed to be well. Checked for suction with my finger over the inlet manifold (with the
carb off).
Looked carefully at all of the carb/gaskets/spacers/heatshields etc. and they all looked ok. Placed the first few back in position and stuck my finger over the hole again, seemed less suction.
RTFPD (parts diagram). Found one gasket in the wrong place. Put it all
back togtether carefully again, and now it runs, but without needing choke.
The weird thing is, it ran with the gaskets in the wrong position for
ages, except needing choke. Then at some point just decided it had had enough and would only run for a few seconds.
Inlet air leaks are a bugger to diaganose, but I should have checked
more closely as I'd already mentioned it.
I thought my posh Hyundai mower had a problem just now. Kept slowing
down and speeding up. Was just about to get the plug out etc. when I
realised it was struggling to cut the lush, no mow, fertiliser enhanced,
May growth. Raised the cut height a couple of notches and it was fine.
The rain was imminent, so I rushed out first thing while the grass was
at its most resistant.
--
Moto Morini 2C/375
Gilera 175 Sport, Husqvarna 401 Svartpilen
Honda CB250RS (Not Waynetta!)
"Do not adjust your mind, there is a fault in the reality"
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