Hi, new here, really stuck and need soem help please

Scoff

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Hi all. Just signed up to the forum as looks like there is a LOT of knowledge here so hoping someone can help me out. I have just aquired a second hand petrol lawnmower which is quite old now, but I cannot get it started. The mower is a Mountfield Emblem which has the Tecumseh BVS 143 engine.
I have checked the plug and is in good condition, am getting a good spark from it. With the plug removed the blade rotates perfectly, doesn't appear bent or warped. I have put fresh petrol in it and the petrol hose from the tank to the carb isn't leaking or blocked.
When you try to pull the starter cord, it kicks back very violently and is extremely difficult to pull - nearly broke a couple of fingers trying for the first time!! After reading up on this the first suggestion seems to be the timing is out - too far advanced possibly, so I managed to get the flywheel off and check, but the key looks perfect and was sitting perfectly in the shaft recess, so it's not a key shearing problem, therefore I assume the ignition timing must be ok as the flywheel can only fit one way so that the magnets line up with the sensor etc.

I am a bit stuck what to try next and could really use some advice. The mower was stored away for a couple years without use if that could suggest anything?

Thanks for any help
Scott
 

173abn

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If it's been sitting that long I'd take the carb off and give it a good cleaning,could be fouled with old gas..russ
 

Scoff

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Thanks, will certainly do that as will no doubt help with running once I get it going. Could that cause the kickback when pulling the starter cord though?

Scott
 

173abn

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Scott,did you change oil?If it's been sitting that long might be rust build up.I'd put new oil in and crank it ,also clean the carb...russ
 

Scoff

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Re: Hi, new here, really stuck and need some help please

Yep I changed the oil straight away as it was pretty black and thick, so it has nice clean fresh oil in it now. With the plug out, the blade does move round without feeling stuck or like somethign has rusted up though. Will try cleaning the carb and see if that makes a difference - would I be able to use a generic guide for carb cleaning or would i need a specific guide for me engine? Just I havent stripped or cleaned a carb before.

Thanks for your help Russ
Scott
 

173abn

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hi Scott,I'd just get a can of Gumout or whatever you all have in the UK for cleaning carbs with,take off the float bowl and clean it up and spray the cleaner in the orfices after removing the needle valves.should,nt be a big deal.I doubt if you can find a carb kit for it but you could try.I might be wrong but I do'nt think that brand of mower is made in the states.you might try to google it and come up with a hit.let us know how you doing in it.maybe someone with more knowledge can chime in..russ
 

Scoff

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Re: Hi, new here, really stuck and need some help please

Thanks Russ.
I have now stripped down the car and it all appeared really clean in side so has obviously been serviced at some point. Gave it all a good clean with carb cleaner spray to get rid of any old petrol traces and checked the float and needle valves - float is fine and sits horizontal and needle valve is fine also - although i think there should be a horizontal spring which holds the needle valve onto the float hinge, but there wasn't one on there, not sure how big an issue this is as the needle cannot come off the float hinge anyway once it is located in its hole as it just moves verically up and down.
The bolt that holds the lower bowl on needs a new gasket/washer really but after removing this, the brass fuel pipe beneath this was screwed all the way down to the bottom of the thread. I have read that it should be backed off about a turn and a half so could this possibly be causing the starting issue? The last thing I will do is just take the crankcase off and check the cam timing is lined up as thats the only other thing I can think it might be. Will post back with results incase it helps anyone with the same type of issue.

Heres a couple pics of the carb opened up before I cleaned it, in the last picture you can see the brass fuel pipe screwed all the way down into the hole, there aren't any o-rings or anything on it and don't know if there should be? Perhaps I will try unwinding it a turn adn a half as per the online isntructions i read..

img00675201108161941.jpg


img00676201108162000.jpg


img00677201108162000.jpg


img00681201108162005.jpg


Scott
 

KennyV

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WELCOME to LMF...

You have checked the normal things that would cause your kick back...
There could be carbon build up in the combustion chamber, that can increase the compression ratio to the point it won't fire right...
check the plug gap... set it towars the widest acceptable limit... and when you replace it leave it very loose... See if the leaking compression around the loose spark plug will allow you to start it without a kick back... if it will start okay, allow it to run a bit before you shut down & snug the plug up... The run 'may' remove some of the carbon build up... :smile:KennyV
PS... use the highest octane fuel you have available...
 

Scoff

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Thanks for the reply. I have stripped the crankcase off and checked the cam timing and that is spot on, so rebuilt it and tried with the spark plug loose but it still kicks really violently on the compression stroke when trying to start. I have managed to fire it up a couple of times and had it running for around 10 minutes now!! The idle fluctuates quote a lot bu probably because i havent renewed any of the air gaskets yet as wanted to get the kicking sorted first. The only way I can start it is by pulling the cord slowly to get past the compression stroke, then a quick hard pull and it seems to fire straight away, although it still takes quite a bit of effort to pull. Unfortunately it is a bit too much for my back though after having spinal surgery ealier this year so I may have to just sell it on for spares:( I hate being beaten though, I just can't work out what is causing the problem. The cord pulls out freely when i remove the cord housing, and the little tab is coming out to catch the flywheel teeth, then returning back in again as the rope is released again, but it just feels like there is something mechanical causing the violent kick.

Scott
 

mullins87

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If you remove the plug wire from the spark plug, does it still pull hard?
 
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