These are instructions for modifying the stock air box on a Suzuki DR350.
Rejetting goes hand in hand with this mod. Performing either the rejetting or
air box mod alone will make your bike run worse - if it runs at all. Performed
together they will make the bike easier to start and include a noticeable HP
increase as well!
Further information and products available at: Jesse's Web site:
Remove the rubber manifold and that will give you access to the screen. The screen is located in the front of the rubber manifold and just pulls out, discard screen.
Remove the carb and take off the bowl carefully. The large jet is the main and the little black hole down inside is the Pilot Jet.
Remove the main jet (using a small blade screwdriver).
Install a 140 genuine Mikuni main jet and close up the bottom of the carb.
On the bottom front you have the fuel mixture screw for the idle circuit that is under a brass plug with a small hole in it. In this picture it has already been removed. Remove the fuel screw cap that normally hides this screw. Carefully drill out the brass plug. It will usually start to spin and just lift out during drilling. You can optionally replace this screw with my Extended Fuel Screw - this makes future adjustments a snap! This screw controls the amount of fuel fed to the idle circuit. Adjust this until you get the highest rpm's (taking it too far will cause them to drop again) then drop the rpm's with the throttle stop to mfr's specs.
Now remove the top and pull out the little plastic step washer then the needle, if your needle has multi-grooves on it, place the clip in the third groove down (from the top).
If your needle only has one grove in it, we have a Performance needle that has five grooves on it. This will raise the needle and give you a richer midrange fuel mixture to balance out with the extra air that you will be getting from the airbox modification.
Once the manifold is out then you can drop the shock reservoir down over the swing arm.
Now remove the mud guard.
Now you can take out the airbox.
Remove the filter element.
Here is the Stock vs modified airbox. To duplicate this draw a square on the top beginning from the right side about a half inch behind the mounting bolt holes across to the edge of the foam rubber trim then straight back to the foam rubber edge, then back across and forward. You should end up with an approx 3" x 4" square now take a jig saw and cut this area out.
Be sure to clean out all the debris and set it a side.
To reassemble the works It is easier to install the carb then the air box and then the rubber manifold fasten the manifold/carburetor joint first then the airbox joint check from both sides to see that the rubber boot is properly engaged with the airbox and carb. Reinstall the shock reservoir and the mudguard and you should be ready to go. Leave the metal filter mounting piece in place it is needed to hold the filter element in place. That's it!