Problems with old dolmar 109

[reyerd]

Have an old dolmar 109 saw. Having problems with after letting go of throttle, it bogs and somtimes dies. Sometimes it revs up and idle normal. Have tried adjusting the screws on carb, h screw is one turn out from stop as instructed in service manual. The l screw is 1 turn out, and a bit more. Only one turn is to lean, and saw wil not go full throttle. The idle speed is adjusted right after chain stop moving. Have cleaned the carb 3 times, cleaned fuel filter, tank vent, air filter, checked control lever and the surface is parallel with carb body, tried spraying start fluid around rubber that connect carb to engine, no reving up. 

If I adjust l screw al the way so that throttle responce is 100%, then it wont idle good, idle speed screw is at max rpm, so now throttle responce is maybe 70% bogs and then revs up. But it is ok for me. But still, letting go of throttle and saw dies sometimes. This is anoying, what can be the problem? Maybe it is just adjustment problems. Have not changed spark plug, can this have something to say?

[hatman-nz]

hi 
have one here   was playing up a bit  and had it  tuned  and new plug   going alot better   
it did get new rings a while back  as the standard filter let a bit too much  fine  dust in  
have had saws in the past play up a bit. new plug and away they do   why no  reson plug looked ok    just seemed to make a difference   
could be worth trying   plugs are cheep