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DRZ400s JD Jet Kit Popping on Decel and Fast Idle when Hot

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Bike Specs:

2006 DRZ400S

Stock Motor

Stock exhaust with spark arrestor removed.

Conditions:

0-4000’ riding elevation (testing at 180’ above sea level)

Testing outside temp is in the 60’s

Modifications:

KN Air filter with 3x3 air box mod

160 main jet

jd blue

clip 4 (counting from the bottom up)

22.5 (stock) pilot jet with extended screw

2.75 turns

What needs fixin:

Massive popping on decal

Fast idle (when hot) (Good idle when cold but won’t start cold without choke full out)

Throttle response seems to be good however; it is lurching while held at steady throttle/RPM’s

Extended fuel screw doesn’t seem to make a difference full in or 3+ out.

I purchased a 2006 DRZ400S with 12K miles. The air box had an attempted 3x3 mod done but no jetting changes were ever done. The bike was backfiring tremendously on decel and would not idle reliably. My TT research lead me to believe the bike was running too lean.

I cleaned up the 3x3 hole and installed the JD jet kit with the above specs based on much reading.

The bike started right up and idled fine.

Once on the road however, the decel pop was just as prevalent as ever.

I also noticed that with the throttle held in a constant position/RPM the bike lurched as if it were losing fuel or getting spurts of fuel.

When I got back to the garage, the idle was high. I adjusted the extended fuel screw and found that even with the screw all the way in the bike still idled fast.

(I hate to admit this part) I tried adjusting the idle screw to bring down the idle but I could not speed up or lower the idle with the adjustment screw.

Getting frustrated, I step away to post for help if anyone still wants to answer DRZ jetting questions:)

Edited by Fullscreen

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I assume youve rode bikes before and fiddled with them so you should know some decel popping is normal. Also, you should definitely run a 165-170 main jet at 4000'. no question. and 22.5 pilot jet? My fcr mx carb stock had a 42 i think? that was too lean for 2000-3000' So I put in a 48. runs fine. the pilot jet should help with the decel popping at least. might help with the idle as well....did you fiddle with your idle speed adjust? maybe by accident?

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A stock 'S has a BSR36, not an FCR, and often uses a 160 main, 22.5 pilot, etc. This thread seems to be getting mighty tangled, mighty fast.

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A stock 'S has a BSR36, not an FCR, and often uses a 160 main, 22.5 pilot, etc. This thread seems to be getting mighty tangled, mighty fast.

You're right, my bad. I think I had about 4 threads up when I replied and I think I meant to high jack one that had similar mods.

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I ended up opening the carb up again to bump the Pilot Jet up to the 25. While I was inside, I took the time to pull the shaft out that the Main Jet sets in and found that it was covered with, for lack of a better term, gunk. I wiped off the "gunk" and put the shaft back in. Installed the 25 Pilot Jet and stock fuel screw 2 turns out. Put it all back together and she fired up and ran GREAT.

So of course I pulled it apart again today to see if a new 22.5 Pilot would fair any better with my $14 Extended Fuel Screw. It still ran lean and while out on the test ride I ended up 3+ turns out and somewhere out on this country road lost the high dollar screw. I kept the RPM's up and dashed back to the garage and put in trusty number 25 with the stock screw. I cut a piece of cork to fit in behind the fuel screw so it doesn't find its way out and ruin a weekend.

Thanks for the help on sorting through this guys.

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