Mountfield SP534 TR 2006 Lawnmower Trouble

Sounds like a small bit of crrap in the system. Only a small amount of fuel is getting through, which is burnt up almost immediately.
You can use a bicycle pump or car foot pump to blow through the carb. If you can, remove all pipes on the carb, turn off or clamp the tank to carb pipe.. Find a good part to fit the pump adaptor to(wrap cloth around a part that is too small if you have to), and pump. Don't ever suck, always blow. Three times, quite sharply, but not enough to launch a rocket.
Refit pipes, pull the starter a few times, slowly enough not to start it(enough to fill carb).
Then give it a go properly.
If it runs, give it ten seconds, then release the choke, full speed ahead.

Mr. HandyAndy - Really

 

I was going to suggest cupping you hands around the tank hole and blowing as hard as you can, but thats not very lady like, .

On the subject of the tank it hasn't go a fuel on off tap has it that not quite fully open (on).

 

From what you describe, it's likely to be fuel starvation of some sort - rather than, say, over-choking.

Removing the fuel bowl is easily the best start - should be a simple task, and also fair chance it could solve it.

Obviously, turn off the fuel tap first. Then, when you remove the bowl, see if you can keep some of the fluid in it so's you can have a look at it - see if there's a different fluid 'beading' around under any actual petrol - that will be water.

Once you pour it out, see if there's any sediment in there - could just be a fine dust.

Also try turning the fuel tap on - if there are no blockages in the fuel line or inlet valve, petrol should trickle out in a thin stream from where the bowl was located.

Depending on what you find at this stage - and report back to us - you may not have to go any further.