X-Man's Hints and Fixes For June 3, 2002:
By: Bobby Baldwin

Idle Air Control Valve     

     The purpose of the IAC Valve is to control the idle speed.  As we are all putting more and more miles on the bikes, it is becoming more common to see these valves not operating properly.  The symptoms of a faulty valve are: fast or irregular idle and/or erratic performance.  Since these symptoms are just about the same as an air leak, you will need to do some tests to determine what needs to fixed.

     If you still have the stock Throttle Body Bracket, check to make sure it is not broken. You can do this by grabbing ahold of the air cleaner cover and try to wiggle it (don't try to break it); if it moves at all, replace it. I don’t want these articles to become commercials for X-Man Products, but you should replace the stock intake system with the X-Man Air Filter Assembly.

     Testing for an air leak is simple. Most air leaks occur around the intake manifold seals, so check them first.  While the bike is running, spray Berryman’s B-12 Chemtool Carburetor Cleaner around the intake seals. Use caution here, because the Berryman’s is extremely flammable! If you notice the rpm’s decrease, you have an intake seal leak and they need to be replaced.  I stock EH OEM seals, but have new seals that work better.

     If the intake seals pass the test, you most likely have a bad IAC Valve.  To test it, remove the air cleaner assembly, including the backing plate. On the throttle body, you will see the two intakes and butterfly valves. Above them, in the center, is the intake for the IAC Valve. Tape over the IAC Valve intake hole. Start the bike and blip the throttle a couple of times. Now, hold the throttle at about 950 rpm. If you can hold it to a smooth idle, your IAC Valve is bad. You have two choices, replace the bad valve, or bypass it.  At this point, there does not seem to by many IAC Valves available. From what we can tell, it is only used on an Excelsior-Henderson.  So, if you cannot find a new one, here is the way to bypass it.

     Plug off the intake hole to the IAC Valve. I prefer making a new backing plate gasket from gasket material.  Next, plug the hole in the backing plate.  Black Silicon works good.  Reinstall the air cleaner assembly.  You will now need to start the bike and manually set the idle stop.  To do this, locate the idle stop, which is on the throttle cable plate, behind the backing plate.  Carefully bend the idle stop with needle nose pliers until you get the idle where you want it.  I recommend the factory setting of 950 rpm’s.

    If you have chosen to bypass the bad IAC Valve, you will loose the “choke” affect that the valve performed. Now, when you start the bike you will need to control the throttle when you warm the bike up. Just hold the throttle to a fast idle until it warms up and will idle by itself.

Thanks to those who requested this and other topics.

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