Motorcycle Repair: High idle on my Yamaha, yamaha yics, vacuum leaks

Question
Hey Wayne, I have a 1986 XJ700 Maxim that idles extremely high after warm-up. I've gone through the carbs, checked the carb mounting boots for cracks, and replaced the boot gaskets. Any ideas on what else it could be?

Answer
Rich,

many of these had idle problems.
Most of it is related to lean idle
mixtures and they are very fussy about
the carbs being synchronized correctly.

Make sure you have no vacuum leaks
anywhere on the boots as you mentioned
or on any hoses. Most of these bikes
have the Yamaha YICS which connects all
the carbs through a passageway underneath
and near the bottom of the head.

These may be part of the problem as they
get carboned up. I will give you a couple of links
to help you understand this system:

http://members.tripod.com/dave_jack/id38.htm
http://home.westman.wave.ca/~jbe/YICS.htm

If the carb sync screws need adjusting, the idle
will be up and down. Also check your plug
color to see if the bike is running
too rich on fuel or too lean.
This will help in sorting it out.
http://verrill.com/moto/sellingguide/sparkplugs/plugcolorchart.htm
Check the air box and air filter, fuel supply
and plug caps.