I have a 2003 KLX 400R. The PO installed a Type 496 Pro Circuit full exhaust with a uni filter. I am at 866 ft above sea level and would like to know what size jet I should use. Its still got the 142 stock jet in it right now. My 09 KLR 650 I went from a stock 150 up to a 160 DJ stage 2.

 

I was going through my klx/drz 400 manual to see if there were any recommendations. Did not see any at the moment. You will have to do the plug chop method, record in your manual your results in your settings. A 1k feet above sea level is not too bad and maybe a couple sizes down on the main, with some needle height adjustment. I would not think it would be too drastic of a change. Good luck