mower hard to turn over after 6 months

[builderpete]

I have a
Blackstock Wheeled Brush Cutter 173 V 137cc WGT 56-173. I used to be able to turn this over with just two fingers as it was so easy. After 6 or 8 months in the shed it is now heavy to turn over and when running only seems to be at half speed which is useless for a brush cutter. Anybody got any ideas. Gratefully received

 

[Auto Doc's]

If it has a blade, it is a "brush cutter", if it has string it is a wheeled weed eater in my opinion. A 137cc engine does not have the power to cut very big stuff.

What engine is on this machine? Is it a Briggs and Stratton with the black plastic carburetor?

From your description it sounds like the fuel system needs to be cleaned. The carburetor has had expired fuel sitting in it and has begun to break down and has sticky gum formation in the carburetor. All gasoline turns to a varnish if left sitting in a small quantity for an extended period of time, especially Ethanol blend pump gas (petrol)