I purchased a 2001 drz400 3 months back. i've not changed the jetting
yet. have checked myn plug looks fine and has been running great!
my stock jetting that was in my bike was a 145 on the main.
have not checked pilot yet . though i'm going to be trying a size or two up to see if i get any better performance. i'm running stock header and a fmf iv.
have't gotton up past 11,000' yet but that will be soon i hope.:cool: :cool:
If the stock jetting works for you now, you can use the chart on the following link to figure out what you'll need in CO. Now, I had a hard time understanding exactly how I was to use the chart, but maybe you can figure it out.
Also, I have a jetting_calculator spreadsheet (XL) that is much easier to use. Just plug in your current jet sizes, alt and temp, and the alt and temp of where you want to ride, and it kicks out the new jet size.
I was going to use it to get jets for a trip to Tahoe, but we ended up not taking our bikes, so even though I bought the jets, I never used them. Sorry I can't vouch for either method, but the spreadsheet did seeem reasonable.