Dear all,
 happy rider of XV1000 since its first days in 81 till 95, I stored it in my garage taking care of starting the machine from time to time. Now, trying again last week (after more than 6 months), it does run on one cylinder. Cause is that the carburator do not feed petrol to the cylinder. Help is needed in finding a way to clean the inside of the carburator petrol reservoir without having to dismantle the lot ...  or any other bright idea will be welcomed. thanks,    

Not much chance you will be able to fix this without taking carbs apart, but try squirting carburetor cleaner into the fuel hose fitting until it fills the float chamber.  Let it sit overnight and then open drain float chamber drain screw.  Reconnect tank and see if bike will run.  Float chamber drains tend to rust closed.  Free them and use them to drain carbs whenever storing bike for more than about a month.  This will prevent recurrence of this problem.  

dear Peter,
You were right ,no choice but I had to dismount the carburator .Guess what,full of dirt ...needed a good cleaning and that's it.All back in order and perfectly working .thanks for your advice .