I am looking to put a stockklx 300 axhaust on my 06 klx 250. Does anyone have any jetting advice?

 

Assuming you are at sea level, use at least a #125 keihin if you are going to remove the airbox snorkel. The stock pilot should be OK.

 

I am about 500 ft. above sea level...Also where's a good place to get one?

I have already removed the snorkel and dropped a tooth on the front sprocket.

Now I am moving on to exhaust and jetting....

 

I'd keep my eyes on ebay. Alsocheck out Thumpertalk.com since people sell them from time to time over there. I would have no issues with aused one, because the stock 300 exaust is tough as anold boot. Ron Ayers stocks most of the OEM parts if you want to get a new one.