Proper Jet Sizes

Hey guys,

Already learned alot on this forum and I've been searching for a similar thread but couldn't find one. Sorry if this is a repeat, here's my situation:

I'm getting ready to take the drz across country from Virginia to Arizona, ranging from sea level elevations to 10k feet. Most of the riding will be around 3-6 thousand feet. What do you guys recommend I jet my Mikuni carb to? I tried rejetting it the other day by using other people's setups as a guide but it is running less than ideal (loss of power from 3/4 to wot, and heavy backfiring) Please Help!!!

2001 DRZ 400s

Mikuni Carb

3x3 mod, slip on exhaust

currently: 142.5 main jet, 22.5 pilot

DJ needle with 3rd clip in

fuel screw 3 turns out

Any advice is greatly appreciated, thanks.

142.5 main and 22.5 pilot are the stock sizes I had in my 400SM... it was surgy and poppy even without the 3x3 mod... I'd say put in a 155 main and 25 pilot (assuming that you're running the Mikuni CV and stock fuel screw).

Thanks PJ, I'm new to carbs but I'm wondering if 155 might be a little large for my expected elevations?

Pretty tough to get a normally aspirated engine to meter perfectly from sea level up to 10,000 feet... I'm assuming that you'll only see the high thin air while crossing the Rockies. I'm no carburetor expert... Maybe somebody with more experience could chime in...

Try 150Mj.....

You need to be testing at the higher altitude you will be mostly riding at, for accurate evaluation..

150 works well, thanks guys.

150 works well, thanks guys.

Do you have the stage 1 or stage 2 needle?

Stage 1.

Before I swapped for the FCR I had this set up in my S. I'm not a jetting expert so I don't know if this was correct but the bike seemed to run well. I think there might be a difference in the needles and the stage 1 needle takes smaller jets than the stage 2 needle. Can anyone with the knowledge of these kits confirm that last bit?

MJ 145


DJ stage 1 needle

Clip on 4th notch from the top

E header with S muffler

PJ 22.5 Kientech extended fuel screw 2.75 turns out

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