Will I do any harm by running too lean by running the stock Harley muffler on my 07? I need to address my idle mixture screw issue, I need to order a new one. Wondering if it's ok to run the bike this way? Stock carb, filter and Harley muffler. No other mods. It pops when I let off the throttle. Throttle responce does seem a bit better and the sound is a little better than the phhht, phhhht, phhht noise that came out of the stock muffler.

Running too lean will increase internal cylinder temps.   Valves and piston tops can glow red, shortening their lives as well as causing pre-ignition.  Pre-ignition can cause the piston to rattle in the cylinder, which can damage it's skirt. The stock Savage already runs lean for emission reasons, which is why people re-jet the carb.  

gort and sevier are both right but depending how far/fast you intend to ride you may be okay. Not good...okay. Quick 10-15 minute jaunts should be fine if you're not trying to push it past 55 or so. If you just CANT wait, and im one of those people, I don't think you'd have a big problem going for a quick ride aside from bluing. It isnt good for the bike by any means but....I personally would do it. I get real obnoxious if I cant ride and even a few miles seems to keep me calm for the rest of the day. As an example...i rode 2k mi or so on new cast wheels...with the rear wheel significantly off center to the right. How significantly? Enough that Im embarassed to admit I didnt just fix it sooner.

im running mine with a new muffler ive richened the screw a bit more but need a pilot jet upgrade i think

Thanks guys. Yea, my screw is screwd.   I did take it out yesterday as I will not be able to for about a week or so at the earliest. It is running a bit leaner. I pulled the 'choke' out to the first notch for a bit and ran great. Didn't go too far, I had to try out the muffler. I like it, a little deeper without being annoying and non of the phffft, phffft, phffft of the stock muffler. Screw should be here Friday or Monday.