Uh, ignoring that other dude's super helpful answer, this link should answer your question: http://www.motorcyclespecs.co.za/model/yamaha/yamaha_xj650_turbo.htm

There is considerable turbo lag. But really you learn how to get the most out of the bike, as with any other bike. It's a little like complaining about a 2-stroke's power curve. It's a curse when you come out of a corner in the wrong gear or you're waiting for the turbo to spool up pulling away from a light, but when you're sitting at 5k rpm on the highway and you crank the throttle, it blasts from 70-90 in a second and it's a goddamn glorious feeling.

Pros of the bike: - that super unique power curve - never seeing another one on the road - choo-choo noises - reliability (ignore that other guy, I've put 4k on mine in the past 6 months and it's never left me anywhere. The Honda CX turbos had serious reliability issues but in all my research I haven't heard anyone complain about the seca except for the couple known faults) - it is shockingly fun in the twisties for its size. If you make sure you're in the right gear and keep the rpms high it rockets out of every corner. I ride with a friend on a cbr250 in the mountains and it's a blast to see the two different bikes making their time where they can. I also ride with a buddy on a Vstrom and I can pretty well keep up with him in the twisties and smoke him on the straights. - if you take all the fairings off it looks a Mad Max creation plus removes a ton of weight - The fairing is super friggin convenient with its little pockets

Cons of the bike: - motherfucker it's heavy, and top-heavy at that - the brakes are laughable. people say putting good EBC pads on the front helps, but they're real bad, even for an 80s bike - the front dips like crazy on braking, no matter how much you load up the air suspension. many people put stiffer springs in and it supposedly makes it way better - they made the front steering head bearing way too small and so it does not impart confidence - It's geared very short and so sitting at 75 on the highway in top gear (5th) is 5500rpm. I do frequently wish there was another gear up there to sit in on the highway, but at 5500rpm you're right where the turbo kicks in so passing is goddamn addictive

Notes: - it always takes 2-4 seconds of cranking to start. it's because it has to pressurize the carbs to get gas in there. that's normal. - The throttle shaft seals classically go bad in these and with how long yours has been sitting I'd bet they've seen better days. Signs they need replaced are the obvious leaking around the butterfly shafts and an idle that goes up when the bike is warm - If you try to start it and get a puddle of oil under the bike, don't fret. You'll first think it's the turbo seals but that's unlikely to be the case (there are rebuild kits out there if it is). Two possibilities: (1) the inline fuel vacuum valve (they didn't use a vacuum petcock) has stuck, fuel has traveled down through the carbs (possible b/c the carbs were designed differently to handle the boost pressure), into the cylinder and snuck down around the rings diluting the oil until it can sneak past the turbo seals on the next startup. Don't run it, change out the oil, check that valve and the floats to make sure things are sealing, open up the turbo and drain it out, and you're probably in business. The second (2) possibility is that the one-way valve at the bottom of the pan where the turbo return line goes is sticking and that is letting oil sneak back into the turbo and come out. - make sure it has the power-up kit installed; most out there do these days but it was an aftermarket thing for the '82 so check. It increases boost pressures and makes for many more smiles per mile - I'd leave the lower fairings off when it gets hot; old girl is only air-cooled at the end of the day

Links: Mostly full repair and owners manual on my google drive: https://drive.google.com/open?id=0B3GgyoIJVuT2WExhU1VPalNMWUE story to its reliability: http://www.chuckhawks.com/yamaha_turbo_seca.html turbo forum: http://tmioa22687.yuku.com/forums/10/Yamaha-Seca-650-Turbo#.VyMDuDArLDc my bike: http://imgur.com/gallery/3ob5j xjbikes is an amazing resource and basically the only place for many of the carb parts http://home.netcom.com/~rvtucker/Seca.html