My jetting setup (2012 300)
 

Just thought I would share my setup. I'm in the mountains southwest Montana and ride 6-10k quite mostly. 6-8k early in the year till the snow melts. Mostly technical single track and I'm a slower B class rider.

I have a 2012 XC 300, all stock.

Running NEDJ Suzuki needle in the 2nd clip, 158 main, and 38 pilot. Did tweak the float height just a touch (leaner). Klotz R50 oil at around 45:1. 91 octane non ethanol fuel. Had this setup for almost a year and about 40 days of riding. Ridden as cold as 40 degrees and as hot as 90 degrees.

Very smooth power with very little hit. Excellent fuel economy. I've done 60 to 65 miles without hitting the reserve. Keep in mind this needle allows you to run a leaner main then the stock needle.

Tried a 155 main but made it too responsive/aggressive for my taste.

I've checked and changed the plug a couple times. Always looks safe, maybe even a touch rich with a darker brown color. Never fouled a plug.

The stock needle gave me more hit, but I really like the smoothness of the NEDJ. Fuel economy was horrible with the stock needle. Less then a 50 mile range.

Love the bike with jetting. Works great!

Nice work. Thats a small main, but appears to be working for you at those elevations. Just confirming, is it a 36mm/38mm carb?

Would have to be a 36 with that setup I would have thought???
:D

Its the stock 38 mm carb.

Again, with the elevation I run and this needle, allows for the small main.

A buddy of mine in town has a 2013 300 and he is running the same setup but with a 155 main.

I just re read your post and you said it allows you to run a smaller main than the stock needle, and just so you know, thats not the case. The NExx and NOZx/N1Ex needles all have very similar fuel supplies towards WOT. Where the NExx needles clean up is in the lower.

Regardless of that, if its working for you thats good. I've never had to deal with altitiude like that before, but I would think the colder temps would balance it out a little too.