Hedge trimmer Engine starts ok but won't Rev up just bogs down

Carby blocked or broken diaphragm

Mix up some "carburetor & fuel injector cleaner" in a batch of fuel, Nathan, at the rate specified on the bottle of cleaner. Run it through the hedge trimmer just like normal fuel. For right NOW, you can use the choke to keep the trimmer running. As the cleaner works, you should need less & less choke to keep it going.

It may take a while.

Next time you store that trimmer for winter, drain it fully and run it until it dies from lack of fuel. Then it won't form varnish on the carburetor jets over the winter - that varnish is what's causing your problems now.

there should be a clutch associated with this machine, eyeball it and check for a broken clutch spring or possible just worn out clutch, good luck

Keep a can of WD 40 handy, spray the workings regularly. Shrubbery is sticky.

The KM90 is a 4mix engine that has valves. You may need to check the valve clearance, using the clearance tool.

Most likely a fueling issue, Check fuel line for air leaks or it could be a carb problem.

could be the air filter needs replacing

REPLACE THE MUFFLER AND IT SHOULD BE FINE.RUST,DEBRIS ECT. CHOKE THEM OFF AND THEY WON'T REV UP.

clean spark plug and gap, remove air filter and clean, look at the spark plug and tell us what color it is, You may need to adjust the fuel mis to get it to run right or you may need a gas filter. Post here with more information.