I have a 1986 Yamaha Virago 1100. It sat for awhile not sure how long though and it didn’t seem to have the power it was suppose to so I changed the plugs and oil and it ran great for a day and half then started acting up and backfiring then lost the power again. When it started I heard a clank inside the carbs I believe this to be the choke or enricher. One cylinder (the rear one) has a fouled out spark plug with black soot all over it. I pulled the carbs and found a vacuum plug broken so I replaced I pulled the bottoms of the carbs and cleaned it up down there then but it back together and put them back on the bike (I noticed that the enricher on the carb for the rear bank was sticking in the up and down postion), and it ran good for a couple of days and has started clanking in the carbs again and lost power as well as backfiring. There is one shop in town out here that works on Yamaha and they have never heard of this problem they said it may be a vacuum problem but they are not sure everything else is more than an few hours away. Is there a way to adjust, rebuild, or do I have to replace them? Is there a conversion kit to go to a manual choke and a single carb?
I think the shop gave some good advice. It sounds like you have an air leak somewhere.
KJS used to make a single carb conversion kit for the Virago 1100’s – not sure if they still do or not. Seems unlikely.
You can certainly rebuild your carbs. Pieces will still be available from your dealer.
I would look very astutely for air leaks. Inspect the intake rubbers, the vacuum hoses, and any internal diaphragms the carbs have. Spray WD-40 or other fluid on with the bike running and see if you can detect a change.
Also, you can download the Yamaha XV1100 Virago Factory Service Repair Manual from my site.