Hyundai HYM40P Stuck pull cord repair help needed!

[Numaticjoe]

Hello everyone,

Last weekend I got a Hyundai mower from a free group on Facebook. The fault was described to be that "the pull cord doesn't pull". When I went to collect it, I managed to get it running literally as soon as I pushed it off the guy's drive. It took a bit to get going but the pull cord was absolutely fine! After I got it home, I managed to cut my entire garden with it. When I went to start it after cleaning the air filter (which was completely dry) it just wouldn't and on one pull it felt as if the cord got caught on something and it just quickly retracted back into the mower. Since then, I've not been able to get it to pull whatsoever. I have checked the basic things such as if the engine was hydro locked or seized which I don't think it is as when the spark plug (which is quite dirty) was out it still wouldn't turn or spew any oil out. It isn't seized either as the piston could be pushed down with a wooden stick. The absolute most I can get out of it is if I spin the blade to the left and then pull on the cord, it goes a little further but still gets stuck in the same place. I'll leave a link to some photos and videos I have taken of it

Video link

I'm extremely new to petrol engines/lawnmowers so I don't know much at all so any help is greatly appreciated!
UK Based
Thanks all!

 

[ILENGINE]

From the looks of the spark plug I am wondering if the head/piston are carboned up and a piece of carbon has come off and is preventing the piston from reaching top dead center which would prevent full engine rotation.

 

[Numaticjoe]

From the looks of the spark plug I am wondering if the head/piston are carboned up and a piece of carbon has come off and is preventing the piston from reaching top dead center which would prevent full engine rotation.

Thank you very much for your reply,
Should I just remove the head and clean off any carbon on there and the piston and replace the spark plug or does further dissasembly need to be done? It did look a little crusty when I held my phone torch up to the hole where the spark plug is.

 

[ILENGINE]

Remove the head for at least cleaning. Then turn flywheel to see if it will make a complete rotation. If it still doesn't rotate then you have bigger issues that may not be worth pursuing.

 

[Tiger Small Engine]

Thank you very much for your reply,
Should I just remove the head and clean off any carbon on there and the piston and replace the spark plug or does further dissasembly need to be done? It did look a little crusty when I held my phone torch up to the hole where the spark plug is.

I have never heard of Hyundai making mowers. Anyway, before removing cylinder head, remove recoil assembly and check it and lubricate it. Make sure pawls that engage flywheel cup are working. Remove spark plug and see if blade and pull start are working smoothly.

 

[ILENGINE]

I have never heard of Hyundai making mowers. Anyway, before removing cylinder head, remove recoil assembly and check it and lubricate it. Make sure pawls that engage flywheel cup are working. Remove spark plug and see if blade and pull start are working smoothly.

Tiger it would help if you would watch the guys short video. The piston is hanging up at what appears to be TDC and will make a full rotation both directions up to that point. Engine is making a clunking noise at that point Also most sounds like a crank hitting a broken rod, but with the debris on the spark plug that he shows I am suspecting a large piece of carbon is jamming the TDC position.

 

[StarTech]

Which if carbon using some decarbonizing fluid may save the day. Just had a FS111 heavy carbon up where it jammed at TDC and fluid save me having to disassemble the unit.

But a valve seat may have cam loose. But it worth a try to decarbon first then pull the if no luck. Also be aware yu may not be able to get parts as even the EU I don't anything of a parts list.