My 84 Westy has had stabilizer valve/ ISCU problems.  The ISCU on the 84 is
behind the plastic panel on the passenger side of the engine bay just behind
the air cleaner assembly. There is a wiring harness leading to the ISCU
through the front edge of the panel.  The ISCU is electronic and not
serviceable. ( I took it apart to see but my problem turned out to be the
valve itself.)  The valve should vibrate ( or maybe buzz) with the ignition
on. Best  to test it with the engine off, ignition on.  You should feel a
vibration when touching the valve.  The problem we had was poorly controlled
idle speed especially during warm up in winter.  I first cleaned the inards
of the valve with carburetor cleaner - that helped, but not goo enough. Then
I disassembled the valve (it is crimped but can be uncrimped) and found that
the valve seat was carbon coated.  This was cleaned off with carburetor
cleaner and a toothbrush  (an old one).  Once reassembled and the crimp
sealed (GOOP works fine) the idle problem was gone. Still working 1 yr later.

To test the ISCU put an ammeter in the line to the valve. This should read
around 400 ma (If I remember right) at idle.  If ma reading is ok and idle
isn't, then the problem is the valve not the ISCU.

Good luck

John

>Anyone,
>
>I've tested my idler stabilizer valve on my 87 Westy and it has continuity,
>yet it does not buzz. Checking the book, states that you should check the
>ISCU. Well that's fine, but where is it? Can it go bad? 
>
>Ed. 
>
>
>"Ask a question and you are a fool for five minutes.  Do not ask, and you 
>   remain a fool forever."  - Ancient Chinese Proverb
>
>
>
John & Dianne Brigstocke
Unionville, Ontario
brigstoc@astral.magic.ca