I have a whopping 200 miles on my new DR650 and the low speed/throttle surge was killing me. I cant afford a jet kit yet so I decided to shim the needle. I had done this on my previous DR650 so I new it was easy and I figured I would take some pics of the process to help those who have yet to do this including my little brother who just picked up his new bike yesterday! If that surge bothers you this trick eliminates most of it. I forgot what a great difference it makes, night and day! It is very easy to do as I said; first remove the side panels, then the seat then the tank. Be sure to disconnect the small vacuum line from the carb to the petcock and don't worry about emptying the tank as the vacuum petcock will not flow without the engine running.
Once you have it stripped down you can easily see and access the carb. Be sure to clean the area around the carb so no contaminates make it inside your carb while you are working on it.Then loosen the cab boot clamps on either side of the carb and rotate the top to the left side of the bike, you may need to loosen or remove the plastic reusable zip-tie that holds the throttle cables to the frame. That will allow more rotation without damaging your cables. Once you have the carb rotated so that you have a clear shot at the cap remove the two screws holding the cap in place. Be aware that there is a spring under the cap so press down on it while removing the screws.
now you should be here:
Under the cap is the diaphragm which is very delicate so proceed with caution and keep everything clean. Remove the cap and the spring then gently pull up the diaphragm which is connected to the slide.
Here is the slide/diaphragm/needle assembly:
The needle just sits down in the slide and is held down by the spring so to get it out just tip the slide and it will fall out. Once you have the needle out you will see a plastic spacer and a c-clip. Remove the c-clip and slide the spacer slightly down the needle and place a thin stainless washer on top of the spacer and replace the c-clip, then snug them all tight to the c-clip:
I used a plastic washer from another carb I had laying around but any thin washer will work as long as it wont rust.
When you drop the needle back into the slide you may notice that it does not hang straight down from the slide. This is due to a shoulder inside the slide. I don't know the purpose for the shoulder but as we are not changing the seating surface I don't think it is a problem. I have heard that some people cut there spacer so that it fits past the shoulder and sits flat but that would require a thicker shim and I feel like there must be a reason for the shoulder so I left mine alone. The reassembly is easy. Just drop the slide back into the carb. Make sure the the diaphragm is sitting flat and even around the top of the carb body and does not get pinched when reinstalling the cap. Also of note: there is a tiny o-ring that seals the vacuum line connection between the carb body and cap. It is visible in the third picture. Be sure not to loose or pinch this little guy. Other than that there aren't any tricky parts, just be careful not to pinch any vacuum lines when you rotate the carb back into place. You will know the carb is aligned correctly when the bump on the front of the carb neck aligns with the corresponding notch on the carb boot.
While I had the carb rotated to do the needle shim I decided to go ahead and remove the plug over the fuel screw and install an extended full screw I had from another carb. The extended screw can be purchased from procycle.
First it is drill (by hand) the little brass cover plug:
Once you have CAREFULLY drilled through this plug you can CAREFULLY thread a small screw into the hole.
Grip the screw with pliers and twist/tug out it comes!
Easy, and now you have the ability to adjust your fuel screw.
This pic illustrates why an extended fuel screw is nice. Getting to that little bugger while the engine is hot is no fun:
Extended vs. regular screw:
Anyway, I hope this helps a few folks with their low speed surge. It really does make a huge difference and doesn't cost anything, also it is a good way for new DR owners to get a feel for their bikes and show you just how easy they can be to work on.