Lawnmower engine constantly seeking/spluttering...
Sunday 2nd September 2012
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Gents,
Hopefully a straight forward one, my Mountfield (B&Q) lawnmower is having some issues. It starts just fine but it seems to be constantly seeking/spluttering. If you turn the throttle down it almost stalls. On choke it's ok (but obviously not meant to be run like that).
Any ideas as to what could be causing this? My immediate thought is maybe there's a governor that needs adjustment but I'm grasping to be honest...
Hopefully a straight forward one, my Mountfield (B&Q) lawnmower is having some issues. It starts just fine but it seems to be constantly seeking/spluttering. If you turn the throttle down it almost stalls. On choke it's ok (but obviously not meant to be run like that).
Any ideas as to what could be causing this? My immediate thought is maybe there's a governor that needs adjustment but I'm grasping to be honest...
Sunday 2nd September 2012
If you are having to use the choke to keep it going it sounds like the carb is crapped up. Strip the carb down and give it a thorough clean especially the jets.
Sunday 2nd September 2012
No sorry, what I mean is that it seems to idle ok when on choke.
Once off choke and set to a high throttle it runs but every so often it splutters (as if it's running lumpy). If on a low throttle it gets worse and has, once or twice, stalled.
Do you still suspect the carbs?
Once off choke and set to a high throttle it runs but every so often it splutters (as if it's running lumpy). If on a low throttle it gets worse and has, once or twice, stalled.
Do you still suspect the carbs?
Sunday 2nd September 2012
Yep, has it got a fuel filter? Have a look at that also.
Sunday 2nd September 2012
Sunday 2nd September 2012
Thanks gents. I will take a look at those items when I get a minute.
I can't imagine it's anything too complicated and hopefully all fixable with my 'short-handled-persauder'.
I can't imagine it's anything too complicated and hopefully all fixable with my 'short-handled-persauder'.
Sunday 2nd September 2012
Before stripping down parts like the carburettor, you'll probably find its simply a small adjustment to one of the two small screws on the carb.
I have a lot of petrol powered garden stuff (ride ons, push mowers, strimmers etc) and I've never had to 'strip down a carb'. They run fine for years, have done for me.
See if you can find the handbook for your mower or the instructions for that particular engine (I'm assuming a Briggs & Stratton engine). There are probably two screws on the carb, one for the idle speed and one for effectively the fuel mix. When the engine is running, gently turn one way or the other, the idle speed screw. You'll find a position (usually within one quarter turn) where the idle speed will smooth out and the engine will run fine at idle. You'll then probably need to adjust the other jet....
It's a balancing act that you won't have to do v often once you it right.
I have a lot of petrol powered garden stuff (ride ons, push mowers, strimmers etc) and I've never had to 'strip down a carb'. They run fine for years, have done for me.
See if you can find the handbook for your mower or the instructions for that particular engine (I'm assuming a Briggs & Stratton engine). There are probably two screws on the carb, one for the idle speed and one for effectively the fuel mix. When the engine is running, gently turn one way or the other, the idle speed screw. You'll find a position (usually within one quarter turn) where the idle speed will smooth out and the engine will run fine at idle. You'll then probably need to adjust the other jet....
It's a balancing act that you won't have to do v often once you it right.
Sunday 2nd September 2012
Sunday 2nd September 2012
No worries. Make sure you identify the idling screw, start with that.
Move it very slowly and mentally note where it was in case you need to return to that position. You shouldn't need to move it more than half a turn maximum to be honest.
Move it very slowly and mentally note where it was in case you need to return to that position. You shouldn't need to move it more than half a turn maximum to be honest.
Sunday 23rd June 2013
Chaps,
Sorry to dig up an old thread but I'm having some problems again with my mower. I'd actually forgotten I had posted this topic before because after posting it the mower was absolutely fine and I don't actually remember doing anything to remedy it.
However, last week my mower developed a weird problem. It's as if it's constantly hunting/seeking. I had a look at it today and the symptoms are as follows:
1. Seems ok on choke.
2. As soon as it's off choke but at a high throttle the mower engine constantly hunts/seeks. The revs rise and fal cyclically.
3. At lower throttles it stalls.
4. The carb has two throttle plates. One that is controlled by the throttle lever itself and a secondary, smaller throttle plate that is controlled by some kind of governor/linkage arrangement. It's this linkage that is constantly moving back and forth when running that is causing it to 'hunt'. Perhaps this is in response to the load varying for some reason but I don't see why it would when idle/not actually cutting grass.
I had the carb apart today and everything looked fine. There was no gunk in it and nor is there a diaphragm that I could see. Just the two plates and in the lower half a float. Everything looks clean and there were no blockages/obvious damage.
The air filter is clean/it makes no difference to the running if the filter is in place or not so I don't think it's an air flow related issue. I also cannot find any idle screw.
Any ideas as to what this could be?
EDIT:
No fuel filter that I can see. Just a fuel line from the bottom of the fuel tank straight into the carb.
Sorry to dig up an old thread but I'm having some problems again with my mower. I'd actually forgotten I had posted this topic before because after posting it the mower was absolutely fine and I don't actually remember doing anything to remedy it.
However, last week my mower developed a weird problem. It's as if it's constantly hunting/seeking. I had a look at it today and the symptoms are as follows:
1. Seems ok on choke.
2. As soon as it's off choke but at a high throttle the mower engine constantly hunts/seeks. The revs rise and fal cyclically.
3. At lower throttles it stalls.
4. The carb has two throttle plates. One that is controlled by the throttle lever itself and a secondary, smaller throttle plate that is controlled by some kind of governor/linkage arrangement. It's this linkage that is constantly moving back and forth when running that is causing it to 'hunt'. Perhaps this is in response to the load varying for some reason but I don't see why it would when idle/not actually cutting grass.
I had the carb apart today and everything looked fine. There was no gunk in it and nor is there a diaphragm that I could see. Just the two plates and in the lower half a float. Everything looks clean and there were no blockages/obvious damage.
The air filter is clean/it makes no difference to the running if the filter is in place or not so I don't think it's an air flow related issue. I also cannot find any idle screw.
Any ideas as to what this could be?
EDIT:
No fuel filter that I can see. Just a fuel line from the bottom of the fuel tank straight into the carb.
Sunday 23rd June 2013
Sunday 23rd June 2013
Just edited above before seeing your post.
There doesn't appear to be a fuel filter at all, just a hose form the base of the tank to the carb.
I emptied the tank today and there was nothing of note that came out either, no gunk/debris.
There doesn't appear to be a fuel filter at all, just a hose form the base of the tank to the carb.
I emptied the tank today and there was nothing of note that came out either, no gunk/debris.
Sunday 23rd June 2013
4. The carb has two throttle plates. One that is controlled by the throttle lever itself and a secondary, smaller throttle plate that is controlled by some kind of governor/linkage arrangement. It's this linkage that is constantly moving back and forth when running that is causing it to 'hunt'. Perhaps this is in response to the load varying for some reason but I don't see why it would when idle/not actually cutting grass.
my mower did this hunting also, causing it to nearly cut out at times. if you tighten this smaller spring you mention it increases the operating revs (considerably), it still hunts but the dip in revs is still higher than the max previous rpm. Sunday 23rd June 2013
If you haven't tried to adjust the governor setting then I would say the gov spring is past its useful life and needs replacing.
If you did adjust the gov arm, try putting it back to where it was.
It's not actually that critical.
It's range of movement should be upto full open on the carb butterfly.
If you did adjust the gov arm, try putting it back to where it was.
It's not actually that critical.
It's range of movement should be upto full open on the carb butterfly.
Sunday 23rd June 2013
Sunday 23rd June 2013
Sunday 23rd June 2013
Mountfield use a 3.5/4hp generic side-valve engine on some mowers. 1. Check the head gasket hasn't gone. 2. Check the rather strange throttle linkage, made of lots of flimsy wire and an air operated governor, it is prone to falling apart.
Monday 24th June 2013
When my old lawnmower with a Briggs and Stratton engine did this, it was always the air filter in need of a clean
Monday 24th June 2013
I fix up mowers and sell them.
Hunting on a briggs engine isn't the springs. You can mask the problem playing with them but that isn't the problem. It will be the gasket and diaphragm, dead easy to replace, cost about £2.
How to
http://www.youtube.com/watch?v=ylo7UAdZWnM
buy here
http://www.ebay.co.uk/itm/Briggs-and-Stratton-Carb...
If it isn't a briggs classic ( you can tell if it is by the primer bulb in the video) and is a mountfield rv150 then you need to give the carb a good clean, air filter cleaned and brush the spark plug with wire brush.
Biggest biggest tip. at the end of the season clamp the kill handle down and run the engine til it runs out of fuel. the carbs are so small they clogg with varnished fuel which prevents them starting. This wil work on any petrol mower.
Hunting on a briggs engine isn't the springs. You can mask the problem playing with them but that isn't the problem. It will be the gasket and diaphragm, dead easy to replace, cost about £2.
How to
http://www.youtube.com/watch?v=ylo7UAdZWnM
buy here
http://www.ebay.co.uk/itm/Briggs-and-Stratton-Carb...
If it isn't a briggs classic ( you can tell if it is by the primer bulb in the video) and is a mountfield rv150 then you need to give the carb a good clean, air filter cleaned and brush the spark plug with wire brush.
Biggest biggest tip. at the end of the season clamp the kill handle down and run the engine til it runs out of fuel. the carbs are so small they clogg with varnished fuel which prevents them starting. This wil work on any petrol mower.
Monday 24th June 2013
Useful tip that, mine normally needs some weld cleaner down the plug hole to get it going in spring
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