TOPIC:

I have an opertunity to get a 1981 honda nighthawk 650 four cylinder, how will this compare to my 750 twin as far as performance, I'm assuming it's 100 cc smaller so it's slower? I have only owned twins so I have no clue what to expect, I would like something with a little more pep. Still keeping my twin I love it but this is a steal

I'd buy the top box.
Steve

a army buddy bought a new one in 1982 and yamaha 750 had a hard time keeping up with

Generally speaking the 4's are faster than the twins.

Look at a gsxr or 600 ninja versus a 1700cc plus harley. I know radical difference.
I owned a kz750 twin, chose to get rid o it and keep my kz550 cuz it was lighter faster and smoother. YMMV

My KZ750 B twin felt like it weighed a half ton and somebody made a mistake at the factory and installed a 49 hp motor.... but it was still fun to ride and had really nice low end grunt with low-mid range torque that made it a joy to ride in the city... especially after I put a 1 tooth smaller counter shaft sprocket on it.

Back when my 650 was stock except for the header, coils and 35 - 40lbs knocked off a Buddy had one and I could always get him on our two lane blacktop in the quarter by a bike or two but as soon as I hit 5th and he hit 5th(They have a 6 speed) he would slowly start walking away from me...... maybe 1 bike at the bridge which was real close to a 1/3rd mile...... think they are 16 valve motors too so a header and a little work could get it quicker yet....... Of course that fairing and bags etc are really weighing it down and he was a good 50lbs lighter than me.

Too bad it's not a KZ. I like the fact it has a one piece valve cover gasket and Honda uses rubber. I wish someone would make them for our KZ's. I believe the valves are adjustable without shims. Looks good, maybe you can fix it up and sell it for a KZ.
Steve

Those SOHC Honda 650's were dogs. A KZ650 will run away from it. Not one of Honda's better efforts.

Kinda a long story here so bear with me I wanna share as this might be useful to someone, so I met this guy to test drive his honda, this was a Craigslist deal btw. So this guy drives to me approx an hour,( trailered the bike) we meet at McDonald's, when I show up he has the bike running off the trailer, we meet shake hands, I take about ten mins checking all the essentials, brakes, lights, tire condition. We agreed before hand I would test ride, so at this point I say ok to your knowledge is everything cooI? I wanna take it on the interstate! He assures me yes, so I hop on and pull out to the road to get on the interstate, I wanted to ride at 45mph before going 65 on a strange bike, now I have never driven a four cylinder, wow so smooth! Not as much torque as my kz twin, not even close actually, but really smooth, so I get to 40 mph and nothing, won't go any more! At this point I'm a mile from McDonalds so I whip a u turn to head back, about half way there the I smell burning something and the front end feels scary, so I go to make a left into the parking lot and boom I drop this bike on its left side bam! Front Wheel totally locked on the turn, I always wear my gear so all is ok, the owner comes running over, helps me pick this thing up and the front caliper (there is two) is smoking, turns out the front brakes when I hit them got stuck on, at first I feel bad for dropping this man's bike when all of a sudden he says, "Oh yeah the front brake lines collapsed and before I came to meet you I flushed out the system and figures it was fine!" so I'm guessing it was letting fluid in the caliper but not back out? So now I'm pissed I mean furious! This guy knowingly let me get on a two-wheeled machine with faulty brakes, had he told me about the issue before hand I would not have ridden it, am I stupid for trusting my fellow man? Yes I guess I am! I was shocked! This person put my life in danger for $450. Look anytime you buy anything this old and used there is problems, that's fine, that's why I feel I gave it a really good ounce over, had he not known about this issue I would have chalked it up to an old bike with bad rubber lines, fine I can live with that. But to know that three hours prior this issue showed up, and to say nothing! Then I got to thinking why would he let me ride it? No cash exchanged hands,I could have totalled his bike and waked off! Then I felt better thinking we'll maybe his is just dumb! Not an evil con artist, I guess I am dumb in thinking no one would do what he did, I mean it it was a car whatever, but a motorcycle! So enough of the rant, Two things I learned, I really want a four cylinder bike, and literally trust no one, especially on Craigslist!

Not sure about this.
I think a more experienced rider would have recognized those brake systems in plenty of time to avoid that... just sayin'.
Oh and that was the time to offer $300.00 and no law suit.

Yeah that's prob a fair assessment, have not been riding to long, stuck brakes was the last thing I thought of!
Lesson learned.

Like Miller said to me when I pulled on his Honda Davidson. "You're learning."
Steve