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non starting mower

Discussion in 'In the Garden' started by jfg, 13 Mar 2019.

  1. Tigercubrider

    Tigercubrider

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    How old is the fuel?
    even easy start or something similar can be weakened by old fuel. Modern stuff goes off really quickly. It also gums up jets.
     
  2. jfg

    jfg

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    The fuel is brand new from the fuel station and the carb was stripped twice and cleaned with carb cleaner.

    There is no seal either on the needle valve or in the jet sleeve that it sits into. I don't recall seeing one either, although that doesn't mean there wasn't a seal in originally.

    So i've scoured briggs bits and found a carb seal kit for the age of my motor and it does contain a tiny red seal.

    I phoned the order through this morning, so hopefully by wednesday i'll having a running mower.
     
  3. Burnerman

    Burnerman

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    Can hardly wait (y)
    As before, not all Briggs engines use this seal and most folks have never heard of it but without it the fuel level is too high and flooding occurs.
    Sometimes a replacement carburettor is the easier option, again GHS usually can oblige.
    Fingers crossed!
    John :)
     
  4. jfg

    jfg

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    After being let down by yet more parts suppliers I have finally got hold of a new seal kit for the carb.

    Unfortunately still not starting, however there is now a slight smell of burnt petrol from the exhaust which wasn't there before.

    Very frustrating. I think i'll buy a new carb and see if that fixes it.

    If not i have a physics defying engine!
     
  5. Burnerman

    Burnerman

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    That could mean that the engine has fired once, maybe.
    Probably off track - what's the oil level like? Is there any possibility that the sump has filled up with fuel at some point?
    Just looking at the original post, where the engine seemed to be hydraulically locking.....definitely fuel related, that one.
    Next instalment, please - if you've any energy left :unsure:
    John :)
     
  6. lostinthelight

    lostinthelight

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    An over advanced timing can have a similar but not so dramatic effect but easily diagnosed by removing the plug lead and pulling it over.
     
    Last edited: 14 Apr 2019
  7. Burnerman

    Burnerman

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    True, but jfg says the flywheel key is sound. The mystery continues!
    John :)
     
  8. lostinthelight

    lostinthelight

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    Very true John but the bit that I cant stop wondering about, especially as I ve seen them fail to start with a slight dent in the key, showing no physical signs of misalignment but displaying a typical preignition resistance.

    “The woodruff is very slightly narrower than the indent in the shaft & flywheel. There is no visible misalignment.”
     
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  9. Burnerman

    Burnerman

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    I haven't much more to offer here, but on the engines I've had with sheared flywheel keys (about 6 I think) - none of them have run, naturally enough - but they do tend to fire somewhere as the spark is still produced. This has involved flame through the carb, explosions in the silencer or somewhere in between :eek:
    I've always noted some damage or marking, either on the crankshaft, the flywheel taper or both.
    At this stage of the problem I do feel that your diagnosis is very likely, but jfg is no fool!
    John :)
     
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  10. jfg

    jfg

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    And i'm back on it.

    I fitted the genuine briggs new carb today, exactly as before.

    I examined the old air filter nd it was black and grimy and stank of fuel.

    I looked at the casing attached to the carb and again it was wet with fuel in the lower part where the air filter fits.

    So back to the drawing board. I checked the oil again, it doesn't smell of fuel but is quite transparent and clear rather than gold or brown.

    I removed the spark plug and sprayed a generous squirt of carb cleaner into the barrel before pulling the starter cord. there was little spray out of the plug hole.

    I'm now wondering if the rings are worn enough to allow fuel past in small amounts and to just not have enough compression to start. The plug just gets wet when i remove to check it after cranking.

    Does anyone know what the compression should be? 500e engine 140cc
     
  11. jfg

    jfg

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    and so as not to seem like a rude tosser, thanks for the help so far.
     
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  12. Burnerman

    Burnerman

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    Been waiting for this :mrgreen:
    Time to ditch the air cleaner for now.....I guess its the paper element type? They are white or light coloured when new :eek: and the engine will be perfectly happy without it for now.
    Just to add to your sleepless nights:
    If fuel sprays from the plug at any time, its too rich to start up. Do you think there is a possibility that the fuel is leaking from the carb and diluting the oil? Best to check by level, but the carb is new now so I wouldn't suspect that.
    Regarding compression, I haven't any figure but if you put your thumb over the plug hole and crank it over, your thumb should be blown off. Sorry, I'll rephrase that :mrgreen: your thumb shouldn't be able to stop the air coming out of the plug hole.
    I guess your right arm muscles will be Popeye like by now!
    John :)
     
  13. jfg

    jfg

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    back again.

    new genuine flywheel key fitted today, spark plug gap is 0.30", coil gap is 0.012", fuel into the carb via red primer button on the side. new spark plug and there is good spark when pulling.

    still no start!!!!

    i was mistaken previously there is no fuel getting into the oil.

    the flywheel fits only in one position and is spot on!!!

    the pull start still sometimes jams when pulling.

    So with so much already done there is no difference to starting.

    I did do a finger test over the spark plug hole and there was some pressure. i'm going to get a pressure testure to get an accurate reading.

    With all i've so far i'm edging towards internal issue, valve or rings.
     
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  14. Burnerman

    Burnerman

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    I'm surprised you have any patience left :(
    With the rocker cover off, you can see the valves operating and when they are closed there should be small clearance which you can feel. On a couple of occasions I have had engines where the pushrod has come off but that is obvious.
    As for compression pressure, I'll stick my neck out and say look for around 90 psi but that's a guess!
    One way to check for valve seal is to pop the engine on its side, have the valve shut and pour petrol into the port - just to see if it leaks through.
    Do post back!!
    John :)
     
  15. EddieM

    EddieM

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    I suppose you have checked the holy trinity, fuel,air, spark?
     
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