My buddy bought a 1985 CB750, Nighthawk S.
Its blue.
She seems to be lacking in midrange and high end power.
She's a great bike, air cooled, four carbs, leather seat, drive shaft. Needs suspension worked on probly.
I don't have a great ear or eye for problems but it seems to run pretty smooth and otherwise decent mechanical condition considering its age 20 y.o.

Any ideas from you long time Honda aficionados or brilliant Nippontuners for pepping up this little gem would be most appreciated.
Thanks!!!!!!

I'll let G post pics of his bike if I can get him hooked up to this sicko cbr site.

Peace,
David

Probably nothing wrong with it. It has a 20 year old set of carbs and 20 year old technology in terms of cylinder head design/camshafts, ignition. Plus it's only a 750 so it is gonna feel soft.

My '69 CB750 felt like a rocket ship when I bought it new. Now, 13.1 in the quarter at 106 mph would get its lunch eaten by a SV-650. Get out stopped and out handled as well.

Nostalgia bikes are better left unridden lest the mists of time part and reveal the warts.

Are you SURE it's a 750, not a 700?? If it's a 750 (from Canada, most likely), it'll feel MUCH different, and some of the parts won't be the same... I used to have a 700... actually, I crashed it in "wrongway's corner" at NeXXt '04! My dad rides it now, since I've got the 'bird...

When you say it seems soft, I know what you mean, because after getting off the 'bird, I can't hardly stand to ride the NH any more... I mean, it's still fun, but the power is... um... a bit lacking, to say the least, after riding the 'bird... When you say it's down on power, what do you mean? It should be a pretty steady ramp up to about 7k, and from 7k to 7500, the power should make a HUGE spike, although it'll still be slow by modern standards, it should make good power from 7500-10k... Does it fall on its face in the upper end, or what?

I did Progressive springs in the front, and Progressive, I believe they were the "13 series" rear shocks out back, and it COMPLETELY changed the bike for the better! Get with Part Monster about parts, because he saved me like $100 over what I could get any of the shops that I'm friendly with down to, and more than that on retail!

Any questions or anything, let me know...

Mike

yes, yes, CB700, my mistake, thank you.

And thanks for the responses.

"Loses power in the upper range", was the owners description. I didn't push it past 6k maybe 7k 'cause its not my bike and I ride like a pussy anyway. Maybe you could steer me to basic maintenance procedures for a this baby? Someone suggested 'sync-ing' the carbs, another suggested a piston rebuild was in order. I dunno. I'll do a little research on my own for 'oldhondas.org' et. ali. And, no, I was not comparing it to the bird's power response

I've been intending to go bother PartsMonster anyway, since he's less than 200 miles from me.

Thanks again.

David


"wrongway's corner" ??? you're kidding, I'm famous!!! ...for being a squid

and you made an offering there too?? of a CB700? wow, i guess we're like brothers or something then...

For years I had a dream of owning a 85+ V65 Sabre, 91+ FJ1200, 1100F (that i have!), and a 700S Nighthawk. I talked with my motorcycle nut brother for months and he convinced me that 80's bikes are indeed, nostalgia and should be left as is. They will break and parts get scarce. His winning argument against them is that I would never set aside time to do all the repairs that WILL come up. So I got the '01 XX and will focus my short attention and lack of free time keeping it cherry instead of a garage of 20-something year old bikes dripping oil and gumming carbs. Leave it as is I say and enjoy the history of it. The 700S is a very cool bike.

Carbs are gummed up... Take the carbs out and clean them... It's a bit of a PITA compared to the 'bird, but hey, it happens...

Yeah, but it was a ~25mph lowside, which I rode back to the hotel from...

Also, TX1100F, my '85 Nighthawk 700S required a LOT less maintanence than the 'bird does! didn't leak any oil, had shaft drive and hydrolic valve adjusters, and got ~50mpg... Old bikes' carbs don't get gummed up any worse than new bike carbs, but they're just more likely to be gummed up when you get it... If you actually ride the thing, they don't gum up at all! This was before I really started doing any real mileage on bikes, but I did ~20k in 3 years on it and didn't have any gumming up problems...

Mike

Thanks Mike, gummed carbs, I believe that. I think I remember some discussion a few years ago about rebuilding carbs on the bird, I'll look for that.

FWIW, I rode my bird back to the 'hotel' and 300 miles back to Baltimore after 'modifying' it at NEXXT '02. Many thanks to Mark, Bigboy's Bandit friend, who gave me some hose clamps and others who assisted in patching me up for the ride home. I went wide on that turn at only about 30+ mph: I stood up after scraping hard parts. I was a novice and I target fixed on the gravel shoulder. A better rider would have easily adjusted his lean angle, and not gone wide at all. Fortunately few trees, wide ditch and no drop off on the outside there.

David

criticism gladly accepted! And you know what?!? Those are excatly the reasons I WANTED a 700S! Read many places that it's damn near bulletproof. I guess my brothers opinions were rightly aimed at my strong potential to get overwelmed and let things go unfixed or unmaintained with a stable of aged bikes deserving TLC (that i didnt give to my 1100F as it's now a restoration project).

I am very happy he (and this forum!) changed my mind and I got my XX! One bike, one thing to focus on. damn ADHD...

I had a 750 s back in the day. It was my first street bike and it seemed pretty fast back in 87, at least compared the 79 blazer i was driving at the time .

I would check the simple stuff first like the fine screens in the tank. I woud also check your fuel i remember mine running tons better on premium. Also the plugs. If it idles well i would leave the carbs alone till you have too. Those bikes were reallt lean in the mid to pass smog test so anything that causes them to lean out more is an issue unless you rejet.

Thast bike was the cheapest to ride i ever owned !!! I paid 2100 in 87, bought a clutch and a few tires, sold it for 2000 in 93 or 4 ... Bw the way if you ever take teh clucth aprt be very aware of how it works, mine had the most compilcated clutch i ever seen, it was a slipper clutch where only half the plates were used when the back whell was pushing the engine.. It took 5 times with the manua to get it together right ! (after someone moved the way i had then layed out )

Herb

If it was the screens in the tank, it would fall on its face at high speed, not at high rpm in first... At high rpm in first, you're still running on the fuel that's in the bowls... I know, because I had a petcock issue, and didn't run out of fuel until ~100mph...

Mine had a standard clutch. Simple.

Mike