Countax mower problem

[daleyd]

Looking for some advice from the hive of knowledge.

A relative has a countax ride on mower - I was using it the other day and it started/ran fine for about 5 minutes, then suddenly started misfiring.

I knocked off the mower drive, it seemed to settle out for a few seconds and then started popping/misfiring again - push the throttle to the choke position and it seemed to run normally again for a minute until it started misfiring and then cut out.

Had a poke around, couldn’t see anything obvious, after maybe 10 mins it started ok again, just long enough for me to get it back into the shed where it started misfiring again until it died.

Sound like a fuel problem? It’s got fresh petrol in, but I’m thinking it may have some sort in the filter, possibly in the carburettor? The fact it seems to run OK for a few minutes seems to me to point to a fuel problem? Anything else worth checking?

It’s a c500h I think, it’s got a briggs 500cc engine in.

 

[Guineafowl]

Yes, sounds like fuel.

Check for ***** in tank, fuel filter(s) - some have a filter in the top of the fuel tap.

Make sure there’s a decent flow from the fuel line at carb connection. Beyond that, take off the carb bowl and have a look, check main jet is clear, otherwise it’s carb off for a full blow out.

 

[cocker]

I would check your fuel filter(s) and carb bowl first .
Sometimes there's a little filter built into the fuel tap .
Guineafowl beat me to it .
Some have a really sneaky filter in the tank !

 

[daleyd]

Yes, sounds like fuel.

Check for ***** in tank, fuel filter(s) - some have a filter in the top of the fuel tap.

Make sure there’s a decent flow from the fuel line at carb connection. Beyond that, take off the carb bowl and have a look, check main jet is clear, otherwise it’s carb off for a full blow out.

I popped the fuel cap off when I got it into the shed thinking it may have been a breather problem but made no difference.

Looks like there’s a fuel filter under the plastic tank, will check that first off!

 

[dan.taylor.1]

You could rig a temp tank up fed straight to the carb and see if it still does it. Would rule out the carb.

 

[GRW]

Modern unleaded petrol doesn't "keep" well. If you've left the mower over winter without draining the carb - the fuel evaporates.... but unleaded leaves behind a varnish-like residue that gums up cards (& the smaller the carb, the more of a problem etc).
It's common.
The symptom of running better on part-choke is classic.
It can also be a swine to clear, as the "varnish is hard to shift, even with copious squirts of carb cleaner & an airline to blow thru the carb body after stripping it.
If you have (or have access to) an ultrasonic cleaner & carb cleaner fluid, I can attest to that working well.

 

[daleyd]

Modern unleaded petrol doesn't "keep" well. If you've left the mower over winter without draining the carb - the fuel evaporates.... but unleaded leaves behind a varnish-like residue that gums up cards (& the smaller the carb, the more of a problem etc).
It's common.
The symptom of running better on part-choke is classic.
It can also be a swine to clear, as the "varnish is hard to shift, even with copious squirts of carb cleaner & an airline to blow thru the carb body after stripping it.
If you have (or have access to) an ultrasonic cleaner & carb cleaner fluid, I can attest to that working well.

It's been fine up until yesterday, and it's had a full tank of fresh petrol a few weeks ago, but yeah its certainly a possibility! I'm hoping it's just filter rather than carb, as it don't have u/s cleaner. Might be an excuse to go shopping though

 

[PhillipM]

On my cheap mower I just bang brake cleaner and petrol 50:50 through it the first fire up after winter for a few minutes, cleans out the varnish just fine. Used to have the same problem of having the clean the carb every time it was stood.

 

[redlig]

On my cheap mower I just bang brake cleaner and petrol 50:50 through it the first fire up after winter for a few minutes, cleans out the varnish just fine. Used to have the same problem of having the clean the carb every time it was stood.

Personally I drain the carb and make sure it runs dry at the end of the mowing season and never have a problem .If I feel rich I treat it to fresh fuel in the spring, A drop of oil in the fuel for last tankfull of the year can reduce the internal rusting of the tank.

 

[GRW]

It's been fine up until yesterday, and it's had a full tank of fresh petrol a few weeks ago, but yeah its certainly a possibility! I'm hoping it's just filter rather than carb, as it don't have u/s cleaner. Might be an excuse to go shopping though

If it's run well this season already, & had fresh petrol then less likely to be varnished - though you can get a flake dislodge & sit in a gallery & cause issues.
Either way it still sounds like carb part-blockage around the main jet or galleries (as opening the choke often allows extra fuel via a different gallery, but also restricts the airflow so it then runs too rich).
If it was a filter, you'd expect stalling, & running choke wouldn't help - so I reckon a carb clean is in your future

 

[Turbo]

Sounds like a blocked filter - any chance it was filled with bad petrol or from a dirty fuel can? Have also seen them filled with diesel!

 

[Smallfry]

It sounds and feels like a fuel problem, but I suspect it is ignition. As said, check for spark. Keep a glove handy for the purpose. As it will be very hot !

I would also change the spark plug as a matter of course.

Fuel problems on Briggs engines normally occur after the winter layup, or gradually make the thing harder to start over time.

 

[Cato]

I think the only thing I'd add to this is to agree with @GRW in that tiny flakes can either dislodge and block or become partially detached and act like a flap when fresh fuel goes through. At the moment I'd say roughly eight in ten running issues I'm seeing re due to varnish build up in the carbs.

 

[Smallfry]

It could be the new E10 fuel has melted the carburettor and fuel lines ! How old is this machine ?

 

[daleyd]

It could be the new E10 fuel has melted the carburettor and fuel lines ! How old is this machine ?

It's not old - maybe 5 years, always been great to start, never had problems and was running fine until the other day. So I don't think it's anything fundamnetally wrong like that, but I need to start with easy/likely things first I guess.

I've got the manual so I'm going to see if I can order a new filter and plugs as a first step, if no joy then it'll be a deeper delve into the carb I guess...

 

[Smallfry]

Maybe we can have another bunfight on the merits or otherwise on battery operated mowers ?

Do check for spark first though, before pulling anything apart, chainsaws are a bu**er for this too !

 

[daleyd]

Maybe we can have another bunfight on the merits or otherwise on battery operated mowers ?

Do check for spark first though, before pulling anything apart, chainsaws are a bu**er for this too !

Well, I probably wouldn't be scratching round covered in petrol if it was battery one, just sayin'

 

[Smallfry]

Well, I probably wouldn't be scratching round covered in petrol if it was battery one, just sayin'

But where would be the fun in that ? What about the challenge to keep ones brain busy ?

Imagine what a dull life we would all lead if everything just worked, and kept on working. Nothing to moan about, nothing to keep that blood pressure up. No reason to throw your spanners about.

Would just have to sit indoors watching yet another repeat of "Homes under the hammer" and looking at this forum on t'internet.

I suppose you could take up Macramé ?

 

[Cato]

But where would be the fun in that ? What about the challenge to keep ones brain busy ?

Imagine what a dull life we would all lead if everything just worked, and kept on working. Nothing to moan about, nothing to keep that blood pressure up. No reason to throw your spanners about.

Would just have to sit indoors watching yet another repeat of "Homes under the hammer" and looking at this forum on t'internet.

I suppose you could take up Macramé ?

Porn? Or if you're reasonably well off, coke and hookers?

 

[daleyd]

But where would be the fun in that ? What about the challenge to keep ones brain busy ?

Imagine what a dull life we would all lead if everything just worked, and kept on working. Nothing to moan about, nothing to keep that blood pressure up. No reason to throw your spanners about.

Would just have to sit indoors watching yet another repeat of "Homes under the hammer" and looking at this forum on t'internet.

I suppose you could take up Macramé ?

I'm currently commissioning an autoclave system for testing materials used in nuclear reactors, I don't really need things that don't work in my personal life as I've got enough here