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Order of procedures for optimum performance: Valve adjustment, then carb synchronization, then pilot screw(jet) adjustment

Mid-range Hesitation

EPA mandated carburetion can result in too lean a mix in the midrange, causing surging or hesitation at mid rpm. This seems to be more of a problem on 700s and V45s than V65s. It can be corrected by raising the needles slightly, which results in more gas when the slides are partially open. Thanks to EPA, the needles are not adjustable, but they can be lifted a little by shimming the needles with 3mm washers. List members report that there probably will be room for only one washer, which may not be quite enough. In that case you might consider installing a jet kit such as Dynojet.

Off-idle Hesitation

This can result from too lean a mix at low speed. Big Brother says no-no to meddling with the pilot screws, except for adjustment needed for different altitudes, which is why they're covered with metal plugs. If you have to drill out the plugs, put a piece of tubing over the drill bit to prevent it from damaging the screw heads.

Idle Drop Method of adjusting pilot screws

(There is a range where the pilot screw creates the highest, smoothest idle. You want to set the pilot screw at the upper end of that range. Screw the pilot screw in too far and the idle drops, screw it in too high and the idle drops = bottom and top of range)

  1. Open the pilots to 3.0 turns. Set idle to 1100.
  2. Start with #1 (really don't matter what number you start at) and turn IN the pilot screw until the idle drops. You can hear as well as see the idle drop on the tach. You've now found the bottom range of the pilot screw.
  3. Then turn OUT the pilot slowly until the idle picks back up. Keep turning until the idle drops again. You've now found the top of the pilot screw range. Turn the pilot screw back in 1/4 turn at a time until the idle picks up. You want the highest idle, smoothest running engine.
  4. If the idle increased past 1100 for this procedure twist the idle screw to back it down to 1100.
  5. Goto #2 and repeat
  6. Goto #3 and repeat
  7. Goto #4 and repeat.
  8. Doing this will get the most efficient burn at idle. Oh... if you didn't mercury synk the carbs then proceed to step 10(shut off bike and go play golf) WHY? Cause you are wasting your time.

After you do the idle drop method, the pilots should be close to the same turns out. The reason they might be different could be many variables: Compression, dirty carbs pilot circuit, un-even throttle plates, valve lash different between cylinders, cam lobe center different between front and rear, dirty intake valves, FLOAT level different between carbs. I am sure there are more but these are the most common.

Read before messing with your carbs:

Motorcycle Jet Kits & Carburetion Basics by Mark Zimmerman

How to Index Your Motorcycle's Throttle to Troubleshoot Carburetion Problems by Mark Zimmerman

Graph of throttle position vs. carb circuit/part used


Do I need to rejet with an Aftermarket Air Filter/Exhaust?

The stock exhaust/air filter is pretty much optimized for the engine in stock form. Drilling the air box is generally considered a "bad idea". Drilling holes in the stock exhaust usually won't require a rejet.

A rejet is not normally needed if you change the air filter to a freer-flowing one (like K&N) and/or slip on mufflers. The majority of back pressure in the stock exhaust system is the collector.

However, if you replace the ENTIRE exhaust system, or change the air filter/box significantly, you most likely will have to rejet.