Since there is soo much talk about jetting DRZ400's with air box mods and exhaust mods I thought I would post my recent results. The mods to my new 2006 400SM went for the most part well.. Learned alot of lessons with my DRZ-400S .The mod part list is: Yoshimura 2165500-SA, DynoJet 3110.001, K&N SU-4000, assorted 4mm Allen head machine screws, and a MotoBits footpeg eliminator stolen from S model. Ebay has MotoBits kits avalible.
1. First I removed all the plastics, seat and tank; I also temporarily removed a couple of the factor zip ties to make room to work.
2. Remove TPS from carburetor, gas line; removed vacuum line from gas petcock, removed vacuum line from gas shut-off valve.
3. Removed throttle cables from carb.
4. Removed gas tank.
5. Loosened right heel guard and dismounted rear break reservoir from frame.
6. Removed bolts at lower frame holding rear fender assembly.
7. Loosened the clamp of the manifold side of the carburetor and the clamp at the rear which connects to the air-box.
8. Raise rear fender – I used an old cardboard box to hold it up in place.
9. Rotated carb and wrestled that booger and out!
10. Installed DynoJet stage two jet kit – 155 main, DynoJet needle (2nd clip from top) and slide spring – when I removed the bowl – I used a needle nose vice grips to break the screw loose – then threw the screws away and replaced them with 4mm Allen socket machine screws of the same length.
11. Drilled out idle mixture screw plug – set idle to 3 ½ turn out from bottom.
12. Re-installed carb - (Note: I also replaced the screws for the TPS with 4mm Allen head machine screws, washers and lock washers.)
13. Removed factory header, exhaust can and passenger foot pegs.
14. Installed new Yosh header pipe – left loose.
15. Separated and installed Yosh mid pipe.
16. Installed exhaust can; tossed the steel spacer and installed the new exhaust mount to the hole rear of the factory mount – I think the Yosh directions may be wrong.
17. Reattached the rear break reservoir and installed and tightened up all remaining frame and mount points, then tightened the header pipe at the engine exhaust, and reinstalled the factory heat shield to the mid pipe.
18. Cut a 3 inch square template from cardboard and drew lines on top of the air box with a grease pencil.
19. I then used a sheetrock knife heated up with a propane torch to cut the 3x3 hole in the top of the air box.
20. Removed stock air cleaner element and installed K&N filter.
21. Reinstalled tank, plactics and seat, cleaned exhaust system with Windex.
1st Test Run
22. Bike was difficult to start –needed full choke (man I should have learned from experience with the DRX 400S!) I finally got it start- but it ran like crap.
23. Run the bike up the street and promptly run out of gas.
24. Roll bike back to garage and do a visual inspection.
25. Put the vacuum line on the gas petcock
2nd Test run
26. Bike starts easily, idles wells and runs great…
27. Removed rubber inserts in footpeg, passenger strap in seat, front reflectors, trimmed rear fender and applied appropriate decals. Performed 1st Oil and Filter change (it had a 100 miles onthe bike.)
If I left out some steps I apologize – but I think you can get the gist of things…