old bike running TOO well

hey guys found this site and have spent FAR too much time here already. my question and or problem is this:
I have a recently aquired 82' Yamaha XJ750 Maxim, i bought it from a family member of a friend, it has roughly 10,000 miles on it and has been stored indoors its whole life. it was parked roughly 7 or so years ago, he had the carb rebuilt 2 years ago, which sat in the box until a week ago, when i and two other buddies went down to try and get it running, long story short we had the carb installed and it rnning in under two hours. problem is it idles at around 2500-3000 RPM's, this weekend i brought the bike home and paid for it, (according to some OVERpaid) and changed the oil, and filter (20W50 and the cartridge filter, when it called for 20w40, ok?? y/n) replaced the battery, and found that in its 7 yeat slumber a mouse had damaged the airfilter, which is currently being shipped here.
any ideas as to wha the problem is? i was hoping since the carbs were rebuilt they would be ok but the more i dig into this bike the more it seems to be the carb, the throttle cable, and choke cable are fine, and the gas tank was flushed out before we ran the bike at all. just looking for some hints, suggestions, or something else. thanks.

 

There are a few carb experts on this site but from my perspective it could be:

* the idle adjustment knob between carbs #2 & 3 might need some tweeking outwards to drop the idle, or

* the butterfly valves controlled by the synchronising screws might need to be adjusted down (in synch), or

* the mixture screws on the front (mikuni's?) of each carb may also need tweaking.

If Richard Massey doesn't come in on this one seek him out on the site - he has pages of carb tips.

 

Just to add to Redcentre's comments.

Start with the idle adjust screw. Metal knob dead center between the middle two carbs (2 & 3). Turn it counterclockwise to reduce idle speed. If you can't get it to idle at 1000 rpm then the carbs were probably not synched or the pilot screws not set to a decent starting point during the carb clean/rebuild.

Look in the FAQ Suggestions forum for "Bench Synching" the carbs. This gives you a starting point to move forward with the Vacuum Synching that is also described in the FAQ Suggestions section.

I'd also read one of the invaluable threads there on cleaning the carbs. Pay close attention to the sections dealing with the enrichment circuit and the Pilot Screws.

I would pull the carbs and do the bench synch, clean and ensure the pilot screws are moving freely and set to 3 turns out from seated. Reinstall the carbs and see if you can then adjust idle with the idel adjust knob. You'll then be ready for vacuum synching and a colortune (another good one to read up on).