Makita DCS 400 not running proper !

[MakitaDcs400]

Well I have a Makita Chainsaw and it usually starts good and it will run for a few minutes you can rev it up fine.  Then all of a suddon after about 3 or 4 minutes it shuts off as if someone hit the off switch.   I have cleaned the carb, changed the plug, checked the exhaust, the gas in the saw is good because my poulan runs fine on the gas.  About 3 years ago a screw fell out of the saw and my brother put a wood screw in to replace it (screwed right into the coil) once he realized why the saw was running so poorly he removed the screw and the saw was fine up until now.  The saw has been stored with gas in it for a month or so without being used (due to the clutch being bad)  I decided to replace the clutch today and found that the saw is running poorly and help or advice would be appreciated.   I wonder if that coil has finally failed ?

[Lewis Brander]

Hello. What I would suggest is to pull the plug once she quits and check for a spark. If there is I would check fuel filter, cap vents. lines, impulse tube etc for any leaks, also you may have to reclean the carb. Just some suggestions. Take care. Lewis.

[MakitaDcs400]

Well I checked it all and found nothing wrong I have recleaned the carb 4 times.  But I did change the saw back over to the old champion plug the new one was an NGK. And now the saw seems to run better.  I'll give you an update later on and let you know if the saw is still running good.
Thanks for the help !