How to adjust idle and/or mixture on Mountfield mower?

Discussion in 'Other Trades Talk' started by RipGroove, May 3, 2018.

  1. RipGroove

    RipGroove Member

    I have a Mountfield HP185 (https://www.screwfix.com/p/mountfie...ary-petrol-lawn-mower/1323f?_requestid=124906) that is surging/hunting when in use. I've cleaned the carb and gapped the plug and put new fuel in to no avail.

    The Briggs and Stratton 300 series engine has a plastic carb with no screws on it anywhere and there are no adjusters on the clutch/brake/cut off lever cable or anywhere on the linkage rods that open and close the carb so I can't see how to adjust anything, maybe the governor needs adjustment?! If I manually push the carb open a little it runs fine, so how can I adjust this?
     
  2. KIAB

    KIAB Super Member

    There is a service helpline number on instruction book.
     
  3. As you suspect, I don't think these have any adjustment on them for mixture etc.

    What sort of governor does it have - is it a wind paddle flap mounted close to the spinning top fan? (You will need to remove the top plastic cowling to see).

    If so, trace the wire link from this to the carb's throttle butterfly, and then continue your 'tracing' of these links (I think with a spring attached) to a lever on the far end of the carb (ie the outside). This lever may be bent downwards to stop it moving, but often you can move it and this will affect the running speed.

    But FIRST check all the other links and check there is nothing broken or missing - often it's a broken spring wot dun it.

    Any chance of some close-up photos of the top of the carb, showing these links and springs?
     
    rich2766 likes this.
  4. RipGroove

    RipGroove Member

    BRB back with photo's, give me a few minutes
     
  5. KIAB

    KIAB Super Member

    According to manual, a engine Manufacturer’s Owner’s Manual is supplied with your mower.

    Horrible things plastic carbs.

    see this link

     
  6. RipGroove

    RipGroove Member

    Not the best photo's as it's tricky to get up close:

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
  7. RipGroove

    RipGroove Member

    The owners manual just shows how to operate and that's it, I'll watch that video now.
     
  8. KIAB

    KIAB Super Member

    Quite a few video's on Youtube about the BS plastic carbs, basically all the same.
     
  9. RipGroove

    RipGroove Member

    Thanks, I'll have another go at cleaning the jets then, I did already put an airline on all the holes in the carb but I'll try again. I'll have to double check but I'm sure while the engine is surging the governor arm was moving back and fourth.
     
  10. KIAB

    KIAB Super Member

    If there a spring on governor arm,try s different one.
     
  11. RipGroove

    RipGroove Member

    Just cleaned the carb as per that video, still surging. The governor arm is moving back and fourth about 5mm while the engine is running? So do I need a new spring?

    If I hold the linkage steady then engine runs smooth.
     
  12. RipGroove

    RipGroove Member

    New spring ordered, will see if that helps when it arrives.
     
  13. RipGroove

    RipGroove Member

    No spring yet but I've tried resetting the governor as per the instructions but when running the governor arm keeps moving back and fourth causing the carb to keep opening and closing which is obviously why it's surging? I can see it happening but can't stop it, and I need to mow my grass!
     
  14. KIAB

    KIAB Super Member

    As a temporary repair, a elastic band can work,still allows arm to move.
     
  15. RipGroove

    RipGroove Member

    A band holding the carb closed/idle? If I manually hold the carb closed against it's idle stop, it actually cuts out.
     
  16. KIAB

    KIAB Super Member

    It should idle,so fuel issues, block jets(not sure if they are fixed ones), use to metal carbs, NOT a fan of tacky plastic carbs.:mad:
     
    Last edited: May 5, 2018
  17. RipGroove

    RipGroove Member

    Well it doesnt lol, there's no idle adjustment on the damn thing anywhere.
     
  18. KIAB

    KIAB Super Member

    You seen above link.

    But, see especially this link, very clear on carb..




    You done jet correctly under float?
     
  19. RipGroove

    RipGroove Member

    Yeah I did the whole carb top to bottom.
     
  20. KIAB

    KIAB Super Member

    [​IMG]

    [​IMG]
     

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