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Merfman 11-30-2012 11:57 AM

1984 CB700SC Nighthawk - first rebuild
My Dad's father owned a garage. My father was an Indian/Harley rider. My Mom's father was a WWII bomber pilot who did what most pilots of that era did when they returned home; he bought/rode a Harley. This rebuild will be dedicated to their memories and I want to pass something to my grandkids, Brody and Ava. I'm just an offroad racer who loves tinkering with bikes and doesn't know as much as he'd like about street bikes. A friend convinced me to ride to Alaska in 2010. (I think he said, I'm going, wanna go?) So, I bought a 2003 VStrom and rode to AK and back and was hooked. Sold the Strom and bought a Super 10 in March of this year. Still, something was calling me... so, after much internal debate, I decided I wanted to see if I had the patience to rebuild a neglected bike. I hesitate to use the "restore" word since I've seen so many beauties restored here. My goal is simply to take a neglected bike and make it a daily commuter and resell it. I want to make something that's an example of an old bike in good working order. Simple, right? I searched the local Craigslist ads for a few weeks, looking for a CB750/550/400 What I found is those bikes are gold and rare as hen's teeth in the condition I wanted. I did find one CB360T but the buyer didn't want to budge on the price and I thought it was a little high... then this one showed up. It's a 1984 CB700SC Nighthawk, rough but in correct disrepair: "It ran when I put it in storage"

Here's my starting place...

I got it home last night and powered it up (battery was dead). Turns signals have issues. No neutral light. Must engage clutch to get it to spin. Won't start. Yup, it's a project! Perfect! :clap

This is my first rebuild unless rebuilding dirt bikes from Louisiana national enduro mudfest counts.

I offer this thread up to those that are lurking and considering their first rebuild. Let's see where this leads...

ValuePack 11-30-2012 02:02 PM

I'm in for sure, love to see some old iron pressed back into life.

rob1313 11-30-2012 02:15 PM

My first street bike was the 750 version of that bike that we got North of the border. Looked about the same. These bikes have/had a bad cam chain tensioner. It's worth looking closely at while you're digging into the bike. Good luck, I'd still love to have one of those, if only to keep it to look at now and then

divotdm 11-30-2012 03:50 PM

I'm doing the same thing to a 1986 700s. Popping out of 2nd gear is i big issue with these bikes. When I was looking for mine, I saw many ads that stated 2nd gear is out. Mine was ( i knew before purchase). I have been working on mine of and on for about a year. Here's a good forum


RedRaptor22 11-30-2012 03:59 PM

Going to be a sweet build, you say your from LA as well, you should sign up on DSRL, maybe get some local knowledge and hands to put to use.

I know my neighbors are some pretty good wrenches, one raced enduro and harescrambles for the past 35+ years, and the other has been building and drag racing vintage bikes for that long.

Merfman 12-02-2012 02:16 PM

What have I got here...
Got the bike home Thursday night. Stopped by the car wash and blew most of the dust, oil, grime and flaky paint onto the side of my truck.

I pulled the battery out, hooked up my jump/charger and after realizing the clutch needed to be pulled in for the starter to engage, hit the starter and was rewarded with a nice, smooth spin. But no fire. Let's review the basics needed for a running engine: Suck, Squish, Bang, Blow. Since it didn't make an unfriendly noises when spinning over, I figure 3 of 4 are working, however, I got no bang. Pulled a plug and am relieved to find a spark. Check. Maybe it was hard to start due to the old gas in the carbs. Drained the carbs and restart. No improvement. Hmmm... I re-drain the carbs and am alarmed by the dribble of gas. Long story short here, I discover what a vacuum actuated petcock is, how it works and realize I probably blew out the diaphragms while using compressed air to clean the petcock. I disassemble/reassemble the petcock about 10 times and cannot get it to hold a vacuum. Needs rebuild and I can't even order parts until Tuesday, which means parts might be delivered in about a week. No way can I wait that long before I know if it's gonna run. I temporarily convert the petcock to gravity feed:

After a little futzing around with choke, throttle, etc, she fired up! Actually seemed to run pretty well and sounded tight. The bike has a skosh under 27K miles on it. Now that I know it runs, I can start work! While I'm waiting on petcock parts, I'm going to pull the carbs apart and give them a thorough cleaning, lube the throttle cables, and tighten everything up.

Teflon2 12-02-2012 04:33 PM

Cool Merf. Glad it fired up!:clap

endurodog 12-02-2012 04:49 PM

Nice work so far, with the dust washed off looks to be in decent shape.

JerryH 12-02-2012 08:08 PM

Best of luck with it. The Nighthawk 700SC was a great bike with a few small issues. It is a bike I wish Honda still made today. It ran great, had plenty of performance for a 700, it handled great and was comfortable. It had cast wheels, tubeless tires, a centerstand, shaft drive and hydraulic valves. It also came with full instrumentation, including a tach. And it looked good. Another great bike Honda dumped. I would recommend pulling and cleaning the carbs, no telling what might be in there. Your biggest problem will be a lack of parts. I rebuilt an '85 Goldwing LTD from the frame up, and parts were definitely my biggest issue. So many of them were no longer available. I got it dirt cheap, in about the same condition as your Nighthawk, and had over $3000 in it before I finished. I got some of the parts used, some from other bikes, some from cars, and had to outright fabricate some. But I had the help of 5 different Goldwing forums. Would I do it again? No. I had no idea what I was getting into. But it was an interesting experience, both fun and frustrating at the same time.

MrBob 12-02-2012 08:48 PM

The 700 was a great bike and designed to be low maintenance. I bought mine on eBay and sold it a year later for what I paid for it.
I found parts on eBay, at a few Japanese bike junk yards and, once in a blue moon, from Honda.
Whey you rebuild that petcock you might want to replace or give the spring a stretch to help it seal.
Really clean versions of this bike seem to sell for a little less than 2,000.00. Mine was 1300.00.

Mike W. 12-04-2012 09:05 AM


Looks like a GREAT start. Bringing a bike back from beater status to something near new can be a huge source of fun and pride... and it can also make you a little crazy:) It's probably a good crazy though... thanks for the post!


ps - I've had nothing but fantastic experiences with these guys for Kawi parts... They say they do vintage Japanese so they might be a useful resource. If someone with an accent talks to you, he KNOWS his stuff.

Bigfeet428 12-04-2012 10:04 AM

I remember those bikes on the showroom floor when I was in high school. Wanted one then and still do. Same goes for a 1st gen interceptor. I'll be following this one.

Yakima 12-06-2012 06:01 PM

Z1 is good.
So is the nighthawk forum. Lots of 700s there.
There's a nighthawk thread on ADV too, in streetbikes.
Sweet bikes. My only ride is a 1985 CB650SC which I've rebuilt into my long distance ride.

Merfman 12-13-2012 07:01 PM

Thanks for all the pointers everyone, great info! As I read more about this bike, I'm pretty jazzed that it's in as good shape as it appears.

Let me introduce a new section to this rebuild report. I'd like to call it "Shit I Learned The Hard Way" or SILTHW, but more on that a little later.

I was last fretting about getting parts to rebuild the petcock. I called Apex Sports here in Colorado Springs (blatant plug) and asked them to order the parts and I was told "We have 3 in stock" - :huh I also got the seat out to a buddy who's gonna fix it up.

Laid everything out..

Out with the old and in with the new..

Checked the operation by applying a small vacuum on the port and verifying it would hold vacuum. Put the tank back on the bike, plumbed the fuel, primed the carbs, thumbed the choke, pulled in the clutch and hit the starter. I was rewarded with a nice idle, sweet!. So Tomorrow I hope to get the carbs out, pulled apart and soaking while I debug the neutral switch. First I have to go to Denver to retrieve some parts a very kind inmate donated.

Oh, about that SILTHW - when reassembling this petcock make sure you use 110% attention to detail. If the little tab on, say a diaphragm, isn't seated exactly, in a spacer for example, the entire assembly will leak like a flea market diaper. When that tab is pressed in until a slight snap is felt, it works perfectly.

Merfman 12-14-2012 09:45 PM

Carb Work
I mentioned my grandfather's garage, found these pics recently, thought I'd share a couple:

Me, Dad, and his Indian, 1958:

Got started on the carbs today. I have enough problems pulling the carb off my dirtbike, I wasn't really sure what to expect on this job. Turned out to be work but nothing to bad.

Here's a short summary of the carb tussle:

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Carbs are out, there was minimal sediment in the bowls, the gaskets looked good but one had some RTV on it so I anticipate some issues at reassembly. After tugging on the carbs for 1/2 hour, I decided to remove the rear fender liner so I could remove the airbox. There was exactly 1 bolt holding the entire thing together and the carbs came out about 10 minutes after removing the airbox. SILTHW - if the gas feed line is petrified, expect the T connector on the carb rails to be the same. It was pretty brittle:

Once the carbs were out, I diassembled each one and started them soaking on SafeTKleen:

Checked each air screw and noted the "TO" (turns out) on each carb for reassembly. Having never tried to adjust 4 at a time, do I put them all back on reassembly or set them all to the setting?

Started the bodies soaking in Pine Sol:

Must remember to remove these:

Didn't have time to work on the neutral switch, maybe tomorrow. Things just need to soak for a while and I'll clean things up a little at a time while parts are soaking.

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