Shimming the carbs
By Chet Walters †

Some exhaust modifications will make the Valk run lean in the midrange. Midrange lean can be corrected with new jets, but that is a lot of work and requires tools and talent. However, midrange flat spots can be lessened with little effort and expense requiring only a few tools (just a phillips screwdriver if you're careful). What you do is add a shim or two to raise the main jet needles. It's so easy it should take you only 20 minutes or so. (But you really should re-jet, since shims are a qwik fix).
MATERIALS
Assorted washers Radio Shack Part #64-3022
 		TOOLS
Phillips screw driver
(one that fits the soft screws of the caps EXACTLY)
only if you raise the tank will you need:
10mm socket
12mm socket

You can do this without raising the tank if you are very careful with the screwdriver. I have an expensive custom paint job. I ALWAYS raise the tank.

Take off the chrome choke cable covers (the long things like angle iron with three screws). Remove the front and rear tank mount bolts. Raise and tilt the tank away from the side you are working on. NOTE: When tipping the tank, please be careful of the things that attach at the rear of the tank. There is a vacuum hose and a fragile fuel petcock. It is possible to tilt your tank without removing these items, just raise the front of the tank and tilt it to the side. You can loosen the petcock with a long small phillips screwdriver inserted into the tube in the center of the knob. Once loose, pull the petcock off the stud. Be careful when you re-install making sure the knob is oriented correctly.

For each carb Take two screws from the cap, being very careful not strip the screw heads (they are soft so use the correct screwdriver). Loosen the third screw. Stick your finger in the middle of the cap and remove the third screw. Slowly raise the cap (there is a spring under there that will send the cap flying if you don't hold it).

Glassp11.jpg (39625 bytes)     Glassp13.jpg (39478 bytes)     Glassp15.jpg (28016 bytes)

Pull the diaphragm up gently and remove the slide. Take one of the cover screws and thread into the top of the center of the slide and pull the needle keeper out. Remove needle and washer. Grab a matching washer from the assorted washer bag and re-install the needle with the original washer and one of your washers (for .020) or two of your washers (for .040) or more. Re-install the keeper, pushing all the way down until it clicks. Invert the diaphragm (make a little "umbrella" out of it). Put the slide back in the carb. Here, the diaphragm will hit the top of the carb before the needle goes into the jet. Tip the top of the slide slightly toward yourself to drop in the needle, then straighten it up to seat the diaphragm. The diaphragm must seat properly, or you'll have a vacuum leak and unbalanced carbs (ouch).

Re-cap that carb and repeat for the other five. Reassemble the choke covers and bolt down your tank. Go for a ride. See if your lean out flat spots are gone. Add or remove washers as needed.

To see if you are running lean or rich, check the color of your plug insulators after running a tank or two. Though the picture above is for heat range comparisons, it matches rich and lean for the most part. Your plugs should look like the center one.