Runs good at idle wont rev after quater thottle bogs .revs good if choke is on

get it running on idle,adjust the idle down till it runs hairy,then adjust low speed mixture screw till you get it highest revs,then keep repeating that till you get it idling normal.rev saw up max revs,adjust high speed jet, in or out till you get max revs,then screw out one quater of a turn.That lets enough fuel thru to cool the sparkplug tip..If thats no good,redo the carbi.Check the tiny filter under the needlevalve hole.Check the needlevalve diaphragm height.recheck gaskets are right way round

When you say it won't rev past 6k what happens? Does it bog down and eventually choke itself out?

sounds like the carb needs a good cleaning. Have you replaced the fuel and air filter? If you take the air filter off does it run better or worse?

Have your carburator adjusted/calibrated/cleaned by a qualified service personnel.

First place I'd check is the carbs - make sure the choke isn't engaged!
Choke on = easy start + easy idle + easy revs + bog under load.

Too much air (hole in the airbox, hose off the airbox) can do this too.

the motor wont rev high on choke.the motor is suppose to fire once on choke. then turn the choke off.pull the start cord and the motor should start and run.check that the throttle conrol is on full. it should run fine.

Any stuck cables or jets or vacuum hose leak?

have u checked the float hight on the carburator? also make sure ur choke curcuit i clean and free of dirt

Check you main jets ccccccthey could need a good wiring through with needle wire cleaners or try running it without any air cleaner unit .If it runs well then could be an air filter problem.

Check for a loose connection by the carb. Sounds like its sucking air.

unleaded fuel is notorious for going stale,and it can leave a resinous coating in the carb-try running the saw on half choke with new gas and less oil eg 50 to 1 for say ten minutes,this should clear the gunk out-if this does not work,you have two choices-strip and clean the carb,or adjust the H (high) scew on the carb anti-clockwise by a quarter turn a time till it revs out full bore-good idea to remove the chain and wear ear defenders when adjusting-and always use a chainsaw at its max rpm,or you run the risk of "kickback"