xj 1100 maxim won't run right

I have an '82 xj maxim 1100. As a bit of background I bought the bike towards the end of last year and it ran fine. It had the 2nd gear problem so over the winter I went through and did the 2nd gear fix. About a month ago I got the bike out and it ran fine...for the first two days. I rode over 100 miles and everything was running completely fine. Suddenly as I was riding the bike started running really rough around 4,000 rpms. It would have massive power loss, backfireing and at times stalling completely. It has been doing this ever since accept the rpm range seems to have shifted a bit lower and it starts running badly between about 2,000 and 4,000 rpms. It will do this whether I am in gear and riding or just sitting in neutral. If I accelerate through the rpm range I can get through it without any issue but as soon as I try to hold a steady rpm it starts to die. I thought that something must have gotten into the carbs so I took them apart and cleaned them completely. I didn't find anything in them that would seemed to be clogging them and when I put it all back together the problem persisted. I am at a loss as to what the problem could be. If anybody has any idea as to what the problem could be that would be wonderful. Thank you to anybody who can help.

 

I have an 82 1100 also. Mine was running badly also this year. So I cleaned the carbs as you did and it still ran funky. I just got done setting valve clearances. The valves were too tight for sure. After two trips to the Yamaha dealer to get the right shims it now runs alot better. More power and seems to be smoother. When I let off the gas I can here the exhaust popping. I still need to sync the carbs. I also put a new set of plugs in also. Let me know if any of this helps.

 

I have had a similar problem with my 750, seems to be the petcock isn't letting enough fuel into the carbs, sometimes it would get slower and slower then die after a few miles and not start back. Right now when it starts acting up I can switch to prime position and everything's back to normal.

 

Check the vacuum going to your petcock and make sure that the petcock is working good.