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Thread: Grrrrr, blast and damn it - f'ing lawnmovers...

  1. #1
    Master
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    Grrrrr, blast and damn it - f'ing lawnmovers...

    Any experts on here - ****ing thing is driving me nuts.

    Was fine after first use from winter a few weeks back for an hour and more but the next week started playing up.

    Mountfield SP42 2019 basic petrol job, just won't run right.

    Little used, petrol clean and fresh, carb clean, jets clear, compression fine, spark lovely, carb linkages all free, safety cut out fine, fuel lines and filter clear etc.

    After cleaning it out I remounted without the air filter assembly - it then ran beautifully and re-started perfectly each time.

    Put the filter assembly back on and lo and behold won't start - eventually did but conks out quickly.

    Logic suggests something has been blocked/moved etc but nothing.

    Air filter assembly off, won't start or run again...

  2. #2
    Craftsman
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    Has it got the little rubber red button to prime it before starting? If so it could be the diaphragm.

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  3. #3
    Is the filter dry?

  4. #4
    Grand Master JasonM's Avatar
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    Thereís a YouTube channel by Mower Man that is good, down to earth guy that goes through the process and likely issues.
    Cheers..
    Jase

  5. #5
    I'd suggest contacting Mountfield direct, chances are they have a customer care/helpdesk.

    R




    Ignorance breeds Fear. Fear breeds Hatred. Hatred breeds Ignorance. Break the chain.

  6. #6
    Master
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    I had a similar problem with my honda went from working to not mower place had to completely dismantle the carb and rebuild only cost about £40 though

  7. #7
    Master
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    Quote Originally Posted by JasonM View Post
    There’s a YouTube channel by Mower Man that is good, down to earth guy that goes through the process and likely issues.
    Was watching him last night!

    Thanks for the replies chaps, I managed to get it re-started after it has gone cold - so definitely a fuel starvation or similar issue I think - will try again in the next few days and see how it goes.

    To answer other points:

    No primer bulb on this model.

    Filter foam is properly oiled but the assembly was fitted without the foam anyway for testing.

    I've had a few outboard engines over the years and fuel varnish/deposits etc are always a PITA. I'm a bit of a luddite in many ways but fuel injection taking over from carbs was a huge leap forward.

  8. #8
    Master
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    Further damn and blast - I'm going to torch this thing soon....

    Following above got it out again - will run for a few minutes before it warms up then starts coughing and spluttering and dies.

    Will restart eventually, gives a few more coughs then some added backfires before dying again.

    F'ing front lawn looks likes I've got into bloody 're-wilding'...

    GRRRRRRRRRRRRRRRRRRRR!

  9. #9
    Grand Master JasonM's Avatar
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    On a similar note, my wife has a video of me trying to pull start a petrol strimmer, on each unsuccessful pull you can hear the chickens freaking out at the noise, its pretty funny, I go on for ages getting more and more pissed off and frustrated until I throw the bloody thing to the ground and walk off in a huff as she is laughing her head off, she then put it to the Steptoe and son music. I would post it but my shorts are showing bum cleavage and its not very flattering.
    On closer inspection the carb was half hanging off as a retaining bolt had worked itself out.
    Cheers..
    Jase

  10. #10
    You need a certain technique Jase, my 70 year old father was always great at pull starting, found it a PITA myself.

  11. #11
    I had loads of issues with a hayter some years back. It was the gasket between the carb and the manifold, it had a tear in it somehow. Changing that cured all the hot start issues.
    Might be worth checking as remounting the air filter might just have finished the gasket off somehow.
    Cheers
    Tim

    Sent from my CPH1941 using Tapatalk

  12. #12
    Master Maysie's Avatar
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    I had similar issues with a brand new Honda mower a few years back. Took it back under the warranty and they tried a couple of times to fix it, but without any success.

    In the end it needed a full ultrasonic clean of the carb as the tiny spec of crud in there could not be seen and would not come out with normal carb cleaning fluids.

    I wonder if perhaps you may have sucked up some dust into the carb when you have been diddling around with the air filter? So may have a similar issue?

  13. #13
    Master Tifa's Avatar
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    Have you stripped and cleaned the carb, and ensured jets are open? A good ultrasonic cleanout can work wonders.
    Also if you haven't already, drain fuel completely...you'd be suprised at the amount of water that can collect at the bottom of the tank..condensate is a really common problem. For irregular running consider swapping out the plug too.
    Good luck.

  14. #14
    Master
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    I always fit a new diaphragm at the start or the season - any small hole can play havoc with starting

  15. #15
    I understand completely and have advice! I had a hardly used mount field mower - wouldnít start, gave it a massive kick which hurt my foot, started taking it to bits, realised it was not made to be dismantled - Put back together even more broken and immediately listed for £50 on the local Classifieds/eBay. Someone then came and took it away from me

    These things really are cr@p not worth wasting your time with, my advice is get something else. I got an electric one from b and q which works fine but there is an annoying lead which I will of course mow over one day.

    Would recommend Honda mowers if you donít mind spending £600 on a mower but they seem to at least actually work.

  16. #16
    Craftsman
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    Regards
    V


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  17. #17
    Journeyman
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    Got a Mountfield about 10 years ago that was half price in a sale. Lasted 2 years before it wouldnít start, took it to a place in Lanark that does mowers and it would be £200 to fix it, which was more than I paid originally. Bought a Bosch electric 42cm instead that I still use.

  18. #18
    Proper carb cleaner works wonders, i think it has toluene in it, devolved all of the gum in the carb, I have got lot of things over the years to run just by soaking and cleaning the carb with it.

  19. #19
    Craftsman Chewitt13's Avatar
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    When I have starting problems, a spray of cold start gets blockages cleaned



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  20. #20
    Master
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    Cheers guys. Yes, Iím sure the carb is the issue here.

  21. #21
    Master
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    As it happens I ‘think’ I may have a brand new carb here - LHP16?
    How ‘east’ East Sussex are you?
    Untitled by biglewie, on Flickr

  22. #22
    My Honda is a bitch at times

    As she has fuel I lie get on her side with air filter up

    Then I spray some starter fluid into the air intake

    She goes like the clappers then for quite a few weeks

    Iíve had all the BS rebuilds new this new that but a YouTube guy suggested the lie in its side

    It works


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  23. #23
    Master
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    Quote Originally Posted by lewie View Post
    As it happens I Ďthinkí I may have a brand new carb here - LHP16?
    How Ďeastí East Sussex are you?

    Thanks very much Lewie. I need to have another go at this one first (itís barely got more than maybe 6 hours use).

  24. #24
    Quote Originally Posted by Max... View Post
    Thanks very much Lewie. I need to have another go at this one first (itís barely got more than maybe 6 hours use).
    They only last 6 hours till they are broken, mine had not even used a can of fuel up - Iím still bitter about it even now.

  25. #25
    Master
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    Donít let it beat you
    Yours free if you need it 👍🏻

  26. #26
    Master
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    Quote Originally Posted by lewie View Post
    Donít let it beat you
    Yours free if you need it 
    Wow, super kind of you. Thank you. Iíll update ASAP.

  27. #27
    Master
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    I had a similar problem with this engine (Iím sure hence the carb) Iím sure it was just the gasket that was letting by- hence I never used the carb just the gasket from the box

  28. #28
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    Hi Lewie - had another go yesterday, even more thorough clean still no joy. My carb looks a little different though, various ways but also my linkages on top are all plastic.
    Last edited by Max...; 28th June 2021 at 11:40.

  29. #29
    Master
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    Quote Originally Posted by Max... View Post
    Hi Lewis - had another go yesterday, even more thorough clean still no joy. My carb looks a little different though, various ways but also my linkages on top are all plastic.
    Have you replaced the gaskets?

  30. #30
    Master
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    The main gasket between carb and manifold is pretty thick and A1 - at the moment running the carb without an air box.

  31. #31
    Master
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    For a couple of £ Iíd order a new set

  32. #32
    Master
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    If it runs without the filter, the filter is the problem. Those pesky oiled sponge filters are a pain. I stopped oiling the filter on one for that reason and it was fine afterwards.

  33. #33
    Grand Master Dave+63's Avatar
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    Quote Originally Posted by tixntox View Post
    If it runs without the filter, the filter is the problem. Those pesky oiled sponge filters are a pain. I stopped oiling the filter on one for that reason and it was fine afterwards.
    This is potentially your problem. Over oiled filters actually block the due from getting through do you suffer from air starvation ragged than fuel starvation.
    Thoroughly clean the filter with petrol and then try it again unoiled.

  34. #34
    Master
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    No - please see other posts - filter is not the issue - it's clean and oiled as it should be but regardless it runs (or doesn't run) just as crap with the filter box as without! :)

  35. #35
    Master thieuster's Avatar
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    The culprit is the E10 fuel. Do not use RON95, use E5/RON98 or Aspen4

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