How critical is low idle rpms?

[outdoortype]

I'm having trouble w/carb adjustments after switching from catlyic converter e-tech to pre etech muffler. I grinded the limiter tabs off the jets & richenend both jets 1/8 to 1/4 turn. The tach says I'm idling around 2800 to 3200 rpms. The specs call for 2700. I richened the screw a tad & slowed them down to 2900-3000 range but the saw smoked when I revved it. The H jet is a tad rich. After about 7 seconds it made it up to 12,700 the first time and then 12,490 the second time. After about 20-25 minutes, the new spark plug was black. I'll lean the H jet just a tad but should I mess with the L jet? The saw accelerated ok before I richened the L jet and idled only a tad faster than with the CAT muffler. I haven't been able to use the search function on this site to I apologize if this topic has been covered. Thanks for the input.

 

[Butch(OH)]

The saw scientists may chop me up here but basicaly an idle RPM range is given in the book because it is both less wordy and easier to understand than saying that your idle speed must be slow enough that the chain doesn't turn but fast enough that the engine will accelerate quickly. In other words don't sweat being out of the book range an RPM or two. Set your idle jet where the saw idles it's best and allows for quick acceleration, sometimes a compromise there. Then set the idle speed slow enough that the chain doesn't turn yet fast enough that you get good trigger response. Remember that both idle RPM and miss adjusted idle mixture can cause a throttle response from idle problem. Then set high speed to tach or by ear in cut if you have ears for such noises. Remembering that the mixture adjustments affect each other to some extent and if off by much you will have to readjust the other.