G'day MM,

There should be a number on a sticker on the end of the air filter cap to check what year this is , that's if it's original or not missing.

Has a LM carby ,I have a habit of just calling them a G4 as LM just stands for Late Model G4.

Some have numbers on the side of the alloy head. Sometimes there is a date stamping on the cast block from memory around
where the carby is but you may need to remove all the covers as it's on a flat surface.

If it's over revving and it's not got an air leak somewhere or running on a lean mixture it's most likely going to need a washer
or 2 in the carby to bring the poppet valve in a more closed position to bring the idle down.

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I'd get the motor running then turn the fuel tap off , see if it keeps a constant rpm when it cuts out or does it scream
to top rpm ,if it revs a lot higher just before it cuts out there is an air leak giving the motor a lean mixture.

Another way to see if the over revving is a motor or carby problem is to put a carby on from one of your other good running
2 stroke mowers and it that fixes the problem you know the old carby needs work.

As Norm mentioned the motor being a Chinese Power torque because the cooling fins are wider apart than the earlier motors.

Cheers
Max.