Hello - hopefully someone can help - we have a Mountfield ride-on mower (about 2 years old) which keeps cutting out at high revs. Ticks over fine on low revs, but stick it into high revs, it runs for a little while (30 secs to a minute) and then just cuts out. My partner has cleaned the carb, taken out the air filter, but it still does it. Could it be the dodgy battery or plugs? Any help gratefully received because I did my daily number of steps yesterday with the push mower!! Thanks in advance
Mountfield Ride-On Mower
- Thread starter Treeze
- Start date
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- lawnmower mountfield
By all means try a new spark plug but the chances are its fuel starvation.....can you tell us which machine it is?
When it tries to pack in, give the engine some choke, if possible, and see if it picks up again.
John
When it tries to pack in, give the engine some choke, if possible, and see if it picks up again.
John
That machine is likely to have Mountfields own engine, against the earlier Briggs and Stratton.
No problem though, the carburettor will have to be removed for a clean, and an aerosol of carb cleaner is essential.
Post a picture of the carb if you want to have a go!
John
No problem though, the carburettor will have to be removed for a clean, and an aerosol of carb cleaner is essential.
Post a picture of the carb if you want to have a go!
John
OK, thanks. I'll check the machine when I get home. Now I've started the thread, I'll hand it over to my partner as he's the technical one. He did clean the carb yesterday, but not sure if it was with carb cleaner or a quick rub on his shirt...! Anyway, I'll be back on here later with an update. Thanks again.
It’s a 1538M. Fuel line was blown through, fuel filter was removed and replaced temporarily with a piece of pipe to eliminate a blocked filter, carb was removed and jets checked, float valve cleaned. I agree seems to be starvation but I can’t see how, all looks ok. I haven’t removed the plug yet. The battery is not good, was having to jump with leads to get started. Ticks over great, but bring up revs runs for short period then cuts out.
Once the engine has started, the battery condition has nothing to do with your problem.
Spark plugs failing under load and heat isn’t unknown so always best to fit a new one, just to rule it out.
When you overhaul these carburettors it is essential to use a proper carb cleaner in aerosol, I have the luxury of a compressed air line too.
Always look for rust deposits in the float chamber before you go any further. I’d take great care looking at the needle valve operated by the float, followed by the main jet and the emulsion tube directly above it but its only a cleaner plus compressed air that will really do - just blowing through jets with your breath isn’t enough.
The fact that the engine runs for ever at slow speed but dies at high revs, where its using much more fuel has to indicate a fuel shortage at this time.
John
Spark plugs failing under load and heat isn’t unknown so always best to fit a new one, just to rule it out.
When you overhaul these carburettors it is essential to use a proper carb cleaner in aerosol, I have the luxury of a compressed air line too.
Always look for rust deposits in the float chamber before you go any further. I’d take great care looking at the needle valve operated by the float, followed by the main jet and the emulsion tube directly above it but its only a cleaner plus compressed air that will really do - just blowing through jets with your breath isn’t enough.
The fact that the engine runs for ever at slow speed but dies at high revs, where its using much more fuel has to indicate a fuel shortage at this time.
John
Once the engine has started, the battery condition has nothing to do with your problem.
Spark plugs failing under load and heat isn’t unknown so always best to fit a new one, just to rule it out.
When you overhaul these carburettors it is essential to use a proper carb cleaner in aerosol, I have the luxury of a compressed air line too.
Always look for rust deposits in the float chamber before you go any further. I’d take great care looking at the needle valve operated by the float, followed by the main jet and the emulsion tube directly above it but its only a cleaner plus compressed air that will really do - just blowing through jets with your breath isn’t enough.
The fact that the engine runs for ever at slow speed but dies at high revs, where its using much more fuel has to indicate a fuel shortage at this time.
John
Thank you. We’ll give the carb another go. Fingers crossed
My mower does the same thing, I was cutting the lawn one day when it just cut out, I fitted a new plug, air filter, fuel filter, flow from the tank, petrol OK works in my push mower, dismantled the carburettor twice. start some times oK or struggles if starting after its cut out managed to get it to run on tick over for 4 mins max or about 1 min on fast speed so all the symptoms lead to fuel but at a complete loss of what to try next.
In this instance I'd pay particular attention to the flow of fuel to the float chamber of the carb.....there should be a good flow of fuel after the filter (pipe disconnected) and then the needle valve, controlled by the float. If it's a Briggs motor, look up for a red circle of rubber where the needle valve seals onto.
Occasionally these swell and fuel supply can be restricted.
John
Occasionally these swell and fuel supply can be restricted.
John
Hmmm!
Not really convinced but delighted that it's sorted.....unless it has the electric shut off on the carb base and the battery terminals were slack.
Enjoy the machine!
John
Not really convinced but delighted that it's sorted.....unless it has the electric shut off on the carb base and the battery terminals were slack.
Enjoy the machine!
John
I don't think that mower has an alternator so the battery has to have a decent charge or it won't be able to provide enough power to keep the plug sparking at higher revs.Hmmm!
Not really convinced but delighted that it's sorted.....unless it has the electric shut off on the carb base and the battery terminals were slack.
Enjoy the machine!
John
Has it got an external coil rather than a flywheel magneto?
John
John
Pass, looks like you know more about it than meHas it got an external coil rather than a flywheel magneto?
John
However, i have a mountfield ride on with a briggs and stratton engine. If the battery on mine is flat i can jump start it but it will stall as soon as the booster battery is disconnected.