Mower engine trouble

Hi All,
I have a Mountfield mower (originally bought from B&Q around 5 years ago) which has a Briggs and Straton engine. All has been well until 2 events... 1. We had a load of building work done and the mower got piled under some other gardening gear and the 2 springs on the carb stretched (net result mower would start etc. but not run so smoothly) 2. The builders used a fuel can for Diesel and I mistakenly put it in the mower :(. Net result tried to start mower (obviously failed miserably) realised my mistake, emptied the tank, filled with petrol. Mower eventually started and I mowed the lawn (albeit with clouds of black smoke!!).
I used the mower a few times after the diesel episode, and although on starting it would have some black smoke, during normal operation, it was smoke free - still not running right though.
All of a sudden, it started conking out after around 10 mins of usage. Taking the plug out revealed it was caked in soot. Cleaning it got the mower going agin for 10 mins... So I... 1. changed the springs on the carb 2. cleaned the air filter 3. replaced the plug 4. got fresh petrol
None of this seems to have made a difference except for the running duration has gone up from 10 mins to enough to mow my lawn (probably an hour and a half or so). Recently though... the 10 mins duration has returned and the same coked up plug and clean remedy!!!
Anyone any idea what I could try next? Should I scrap it?
thanks in advance for your help
Lee.
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The outer of the throttle/choke cable not being held firmly? I've had to use cable ties to fix the cables to the handle. Before fully tightening the ties start the motor, adjust the throttle position and pull on the cable outer to set the correct speed.
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Alan
news2009 admac myzen co uk
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On Saturday, 7 July 2012 09:53:38 UTC+1, Alan wrote:

Hi All,
I have just stripped it down and discovered the following.... - valves and piston caked in soot (now cleaned) - fuel filters a few bits in but nothing to write home about - diaphragm started to peel away from the rubber backing (ordering a new one now!!).
So, looking like the diaphragm is the culprit.
One question though... Since I have taken the head off, do I need to replace the head gasket/ put some gasket sealer on it or just bolt it back on?
thanks all and I will report back once the new diaphragm is fitted.
thanks
Lee.
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Lee Nowell wrote:

advisable, yes.

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To people who know nothing, anything is possible.
To people who know too much, it is a sad fact
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Going Off Topic a bit I'm afraid, but can anyone explain why I can't get YouTube to work - I've been getting a message for a day or so now saying that "An error occurred. Please try again later"
Rob
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robgraham wrote:

From reading elsewhere, the latest Flash update (version 11.3) refuses to play nicely with the Realplayer 15 downloader. Going back to Flash version 10 cured the problem for me on Vista and 7.
Oldapps have it cached here:-
http://www.oldapps.com/flash_player.php?old_flash_player 
--
Tciao for Now!

John.

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wrote:

Thanks John - I'll go and pursue. Rob
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OK - replying to my own posting. I found that the problem was related to Chrome only - if I used Firefox it was OK. A bit of Googling found that this wasn't an unknown problem and the recommended solution was to go into the 'Spanner'/Settings/Advanced/Content Settings/Cookies and Site Data .... and then search for and delete all the YouTube cookies.
Rob
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