Smoke from engine of lawnmower

Usually this is a sign of oil being in the ignition chamber. Check the oil level, if too high drain and refill to proper level. Also if you have hills or slopes in your yard make sure that you are mowing up and down not across. If you must mow across the slope make sure to do it with the oil to the downward side. Caution if you do this too often the engine will be deprived of oil all together and seize up.

first check for spark when it dies then check to see if the needle valve seal swelled up from our current fuel

Hello,
I think that will find that the wire strainer has become blocked in your engine breather system. Unfortunately the engine breather for your engine is located under the flywheel, the flywheel will have to be removed with a puller as this is a taper fit on the engine crankshaft and usually a very tight fit ( especially if it has never been removed before ), once removed you will find a small cover held on with two 6mm bolts, remove the cover and you will see a wire stainer, wash this out, and if possible blow it through with compressed air until you can see through the wire strainer when you hold it up to the light, refit all parts and hopefully you will have many more years service from your lawnmower, I write this as I have a garden machinery repair business in Chedzoy, Somerset, England and have had a very similar problem with a customers lawnmower, best of luck and happy mowing.

Nope. If the grass is too high, knock it down to size with a weedeater first. These electric mowers cannot handle the tall, high stuff. If you do, you will surely burn it up.

There is a few things that I would check and might come to a solution to your issue follow this and will help diagnose your mower. Has this engine been over filled with oil?
Has the lawnmower been turned on its side to clean?
Has it ever been serviced because the carburettor diaphragm and air filter need to be changed on a yearly basis.

i had the same problem i talked to a repair shop and they said the coil was going bad and when it heats up there is a short in it (follow the spark plug wire back to the motor and the coil is there ) i replaced the coil pack and problem solved, hope this helps.

Carb needs cleaned as it can't handle the load of the engine and the deck at the same time. My guess about the spark plug melting is that the electronic ignition may have become hot while trying to start the mower causing the wire to melt.

JCB LS45 specs Manufacturer: JCB
Blade Length in cm: 42 cm
Blade Width in cm: 40 - 44 cm
Cutting Width in cm: 42 cm
Electric Start: with Electric Start
Grass Collection Bin: Back
Horse Power: 3.5 hp
Mowing System: Rotary
Power Supply: Petrol 2 Stroke
Type: Walk behind mower

check motor if armature are not broken & see if the rectifier not burnt. rectifier works from ac & convert it to dc to run the motor.
if you need diagram for parts see toolpartsdirect.com