I am assuming you have everything in the carby adjusted properly. The most important thing to check is the diaphragm is sealing. I have detailed the procedure behind checking this above. The same process applies for power torque and full crank engines when it comes to diaphragms.
If the diaphragm is sealing you could try adjusting the governor port on the cowl. Start up the engine with the governor hose connected to its port on the cowl. Make sure the engine is at full speed and twist the governor port left or right and you will notice the revs will adjust accordingly. The little wheel you click the hose into turns both clockwise and anti-clockwise. Just find your sweet sounding midpoint.
Lastly if that doesn�t work check your top crankshaft seal. These engines start with top seals cracked however they rev way to hard because they are leaning out due to excess air entering the combustion chamber.
To check the seal remove the flywheel and dribble a little 2 stroke on the seal and then rotate the crankshaft to check for bubbles.
Bigted will no doubt be able to add additional detail if I have missed anything.
Please make sure you wear appropriate safety gear when making adjustments to running engines.
PS. These are great engines. I still get a fair few through to repair and they all end up being great runners for relatively very low cost.
Jaffa.
