I used to have an `86 750... When I removed the airbox, I struggled with the thing for about 45 minutes after removing the carbs... and finally just took a hacksaw to the thing to get it out. I'm *told* that it's possible to remove it intact, but I don't actually know anyone who has done it. You *definitely* want the carbs out first, and the little rubber boots that the carbs go into on the cylinder head come off too... and if it's important to you to keep it intact, I'd suggest lots of patience.
I have the exact same bike. I screwed around with that damn air box for a good hour trying to figure out how to get it out in one piece. I was so pissed off by that time I broke it to pieces with my hands. I knew that the stock air box was'nt ever going back in, so I was'nt worried about how it came out.
I asked a buddy of mine who is a m/c mech how to get them out, he said "you have to pull the motor to get it out in one piece". I BELIEVE him.
Those are you two choices, hacksaw or pull the motor.
Well, K&N and UNI both make individual filters that will fit, but you do *not* want to just plop individual filters on even with the stock exhaust... the bike will run like crap, if at all. There are "jet kits" that K&N and Factory sell for your bike, and that's what ya gotta use if you want the individual filters... note, if all you're trying to do is change the stock air filter, there's no reason to take the airbox out of the bike... there's a 10mm nut that holds a cover on the airbox and that's where your OEM filter is... easy as cake once the gas tank is off the bike.
I have a set of K&N individual filters that will fit your stock carbs that might be for sale (I'll know in a week or so)
I bought a set of 36mm flat sides for my bike, but I'm considering buying a new 1000. If I buy the new bike I will have to sell the 750 and I would put the stock carbs back on & sell the flat slides. If I keep the 750, I would sell you the K&Ns. If your interested let me know.
Be patient young man. If you remove the carbs, and all the little brackets from the airbox and the frame around it it will come out intact. A spray with WD40 or silicon will help it slide on the frame.
I've popped mine in and aout a few times since I started the carb fiddling. I took it out for good for the top end work and set it in a box for safe keeping.
i tried takeing it out again today ! with out luck ! that thing is a bitch and a half and i took a big chunk out of my hand , blood everywhere so i said fuck it and it can stay in there for now !!! untill i find the money to replace it with some good stuff!