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Discussion Starter #1 (Edited)
The other day a friend of mine texed me, wanting to know if I'd be interested in buying a motorcyle. He's in the military, was about to transfer back East, and the person who was originally going to buy the bike changed his mind at the last minute. I'm always interested in buying motorcycles, but that doesn't mean I'm in a financial position to do so whenever an opportunity comes around. I texted back and asked what he had, and what he wanted for it. He had a 1991 Honda Nighthawk 750 with 9,000 miles, and was asking $200. It had a title, but the key was missing. It had been laid down a couple times on both sides, and it hadn't been running in more than six years. Despite the minor road rash, it was in good overall condition, and I gladly handed him $200.

Left Side.jpg

After reading numerous internet posts about the '90s Nighthawk 750s, I can state with some certainty that there is nothing special about one. The are best known for being simple, low maintenance, reliable bikes, with average handling and just adequate braking. Something I kept seeing mentioned was that it was "built by committee." The downside of reliable, low maintenance, built by committee bikes, is that they generally don't have that edginess or oddity which would eventually lead to desire. As a result, nice, used examples of these bikes are pretty inexpensive. So, even with a good overall condition, $200 example, it's important to make sure the damage which needs to be repaired doesn't cost more to fix than what a ready to ride excellent example would cost to purchase.

I looked over the bike and found the following: seized front brake, all four turn signals broken, 28-year old original tires, dead battery, six-year old gas in the tank and carbs, scraped mufflers, headlight and mirrors, missing key, minor scratches in the paint, and a need for fresh plugs and an oil change.

If I ignore the cosmetic stuff, and just worry about getting it running and road worthy, I am looking at less than $500, with the majority of that money being spent on tires and carb rebuild kits. Seven hundred dollars for a good running bike in fair cosmetic condition is pretty reasonable, and it should have reasonable sale value on Craigslist of between $1,500 and $1,700. Not a bad return on investment. Replacing the scraped mufflers and headlight would significantly add to the refurbishment cost. Good headlights were running over $80, and good, full exhaust systems were being offered for more than $300 plus shipping. While these parts would make the bike look better, there is no telling if it would actually significantly increase the sale value. If I happen to find the cosmetic parts I need for a good price I'll buy them, but for now they are not high on the priority list.

Today I got a little time to work on the bike. The first thing I did was remove the seized front brake caliper. I unbolted it from the fork lower, then used a 2x2 and a mallet to slowly ease it off the disk.

Brake 2.jpg

That only took a couple minutes, so I decided to remove the ignition lock next, so I could get access to the key code stamped on it. With that code, my local Honda dealer can cut me a new key in a few minutes for just $10.

Ignition Removal 1.jpg

Everything went quickly and smoothly until I tried to remove the Torx bolts which are used to mount the switch housing to the underside of the top triple tree. I actually broke two teeth off my Lisle T-40 Torx socket, stripped the bolt head, and split the fingernail on my right thumb for good measure. It's not a worthwhile project unless you're bleeding. I'll now have to remove the top triple tree to drill out the stripped bolt, and buy a new T-40 socket to try and remove the other bolt.

Broken tool.jpg

Sorry for the horizontally posted vertical photos. I tried to fix them but the kept posing with the wrong orientation.
 

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You can hardly go wrong for $200.

I moved your post to the project logs section, it looks like one!
 

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Good score. When in good shape that bike will be an appliance, keep it full of air, gas and oil and just ride. If you paint that top triple don't use gloss black, ask me how I know...
You can fit a much wider tire on the back, I had put a 150 on mine, it was very stable for highway but handling was terrible when riding with the guys.
I had put Michelin Pilot Activ on and they were great in all weather but didn't warm up all that well under 35F temps.... I went up 2 sizes on all jets, #37 and #117 I think, I got 55mpg regularly with a thorough thrashing. I've got the stock jets if you need them, after a decade in a jar of carb cleaner they should be clean by now. Yours for postage if needed, send a pm.
I also recommend All-Balls brand steering bearings, wheel bearings and fork rebuild kits, good quality and all the seals included. Forks take a full 16 oz from clean and dry, Honda sells it in 16 oz bottles, so very easy there, I think I used 10 weight. Oh, I had found oil filters at Pep Boys, so no need to panic if you forgot to order. I ran Rotella T, very smooth and it tells you when to change it.

Congrats, if you flip it, it'll sell. But if you keep it you won't be sorry.
 

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Discussion Starter #4
I managed to get a couple things done to the bike today. The first and easiest was removing the pads and clips from the brake caliper, so I could spray the pistons with some PB Blaster before I try to remove in a day or so. I have a couple ideas about how to do that. It would be a lot easier if it was a single piston caliper, but it's a two.

While I was out running errands today, I stopped by a local tool shop which deals in high-end, made in America tools, Proto, SK, etc. (think of it as brick & mortar tool truck). They had a replacement for my T-40 socket, and said there would be no charge because Lisle has a life time warranty on it. I've had it, and the set it goes with, for more than 20-years, so that was a good investment.

Next I continued working on removing the ignition. After stripping the one of the two Torx screws which hold it to the bottom of the top triple tree, it became obvious that the only way I was going to get it off was to remove the top triple tree, so I would have more access to them. This required disconnecting plug for the ignition, which is inside the headlight housing, disconnecting the clutch cable (which for some reason passes though cast-in cable guide on the front of the top tree), and removing the handle bars. Loosening the pinch bolts, which clamp the tree to the fork tubes was pretty easy, but naturally I did not have a socket the correct size for the stem nut. As a result I did what I've done a number of times in the past: Use a socket which is slightly larger than the nut, while using a thick rag to take up the space. In this case the metric nut was approximately 1 3/16", so I used 1 1/4 socket with a terry cloth rag to fill the gap. Stem nuts never seem to be on with very much torque, so it usually takes steady, gentle pressure to break it loose, and I have yet to damage the chrome on a stem nut.

Top Tree Off.jpg

With the top tree removed, I flipped it over and put it back on the forks upside down, so I could apply the leverage needed to remove the two screws. I could have clamped it in a vice, but I would ended up damaging the finish as a result. The undamaged screw came out very slowly using the T-40 socket and a breaker bar. I then used a hammer to tap the new socket into the stripped out screw. I managed to get it moved about two full rotations before what remained of the screw head finally gave out. I then grabbed my drill and a 3/8" bit. It took between five and 10-minutes to drill though the screw head and release the ignition. Now here's the rub: When I was triumphantly admiring my freshly freed ignition in the light of the kitchen, I noticed the lock code, stamped into the ignition body right next to the fork lock pin. The ignition does not have to be removed from the top tree, but you need to remove the top tree to see the code. No big deal, I'm out a little time and a 30-cent screw. This will also give me the chance to everything in the triple tree area a lot better.

Screw Drilled out.jpg

Tomorrow I will try to find time to get to the Honda dealer to get a new key made, and work on removing the rest of the screw from the top tree.
 

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I enjoyed my 1991 Nighthawk 750. I purchased it used from a local Honda shop back in 2000-2001 for 4k. I enjoyed the UJMness of the bike and quickly moved on. It is one of the bikes I wish I had kept.
 

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Discussion Starter #7 (Edited)
I managed to get to the Honda dealer today. I spent 15-minutes and $15 and got two new keys. This dealership has been around for quite awhile, and they told me they actually have a pretty good inventory of new old stock cut keys for older Honda's (the one's with the four-digit code stamped on the key and locks). If you need a key for an old bike it's worth a try to see your local dealer.

New Key.jpg

The only other thing I did to the bike today was come home and check to make sure the keys open the tank lock and seat lock. They do. The six-year old gas smells nasty (but I've smelled worse), and the only things under the seat were the missing license plate (last registered in 2002), and a service manual print out describing the ignition system (this could get interesting). No owners manual, or tool kit. Oh well.

I'm not in a hurry to get the pistons removed from the brake caliper. I'm happy to let the PB Blaster soak awhile to ensure they come out ok. I watched a video on refurbishing calipers, and it suggested using fine brass wire wheels in a Dremel Tool to remove any corrosion in the piston bores, so I'm going to source a couple of those before I start. I looked up brake rebuild kits the other day online, and the prices ranged from around $10 to almost $40. I asked about availability while I was at the dealer today, and he could get one for about $20. Considering what the parts are for, I'll go ahead and get them at the Honda dealer (once I know the caliper is salvageable).
 

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Discussion Starter #8
I've spent a couple hours now trying to bleed the front brakes and build enough pressure to force the pistons out of the capliper. I am beginning to suspect the master cylinder needs a rebuild. It is moving fluid, but not in the quantities it should. Over the course of an hour I only managed to pump one resevoirs worth of fluid. During that time I never felt any pressure build, and the pistons never moved. Also, a normally functioning master cylinder should squirt fluid up out of the resevoir if you pump it too fast. I pumped fast and slow, and never once got a squirt of fluid out of the master. This bike isn't new enough to have a bleed screw on the master cylinder (I looked). I did some internet sluthing and found a suggestion I'm trying now: zip tie, or use some other method, to compress and secure the brake lever, and leave it like that over night. Supposedly this will allow any air bubbles in the master cylinder, and possibly the brake line, to float up and escape into the reservoir. I'll see how well this has worked in the morning. If nothing happens I'll be ordering a cylinder rebuild kit, luckily they are cheap, and it's an easy task.
 

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I had the same problem on a cb400 master cylinder, replacing mine made more financial sense than a rebuild kit. Now it'll pump brake fluid out the bleeder no problem.

Also I've found reverse bleeding (pumping brake fluid in through the bleeder and up into the MC) much easier, there's tons of youtube videos on it. I don't know if you've got dual front discs and whether or not dual calipers would complicate that process.
 

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Discussion Starter #10
80CB400t: Thanks for the tip on reverse brake bleeding. I watched a couple videos on YouTube, then went out looking for a large syringe, or a kit to do it. My second stop was the local Kawasaki dealer. I asked if they had any reverse bleeding kits in stock. They didn't, but the mechanic had a couple large syringes on hand (it never occurred to me how handy those things could be until I started watching the videos), and gave me one for free. Just because you own Honda doesn't mean you can't find things you need at other dealers! I still need to get some fresh tubing before I give it a shot, but I should get a chance sometime this weekend.
 

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Discussion Starter #11
Last night I finally got around to trying out the reverse bleeding method for the first time on the front brake. I was worried something was not going to go right, and I would just end up wasting an hour or two in the cold. As it turned out, this is the easiest brake bleeding method I have ever tried. The only problem I had was not cracking the bleed screw open far enough at first. Once I figured out my mistake the fluid injected into the caliper very easily (just take it slow and steady). I was amazed at the amount of air I could see bubbling out of the master cylinder reservoir. I will definitely do this in the future. Below is the simple set-up I used to reverse bleed the brake, just a larger syringe and clear vinyl tubing which fits tightly over the bleeder screw.

Reverse Bleeder.jpg

Once the brake was bled, I turned my attention to removing the pistons. Single-piston calipers are pretty simple, you simply pump the brake until the piston finally leaves the bore. Multi-piston calipers are a little more difficult, because you have to get all the pistons out at the same time, and if one stuck the others will come out first, leaving the stuck one still in the bore. One of the YouTube videos I watched showed how to use a stack of shims to allow all the pistons to come out at the same time. You stack the shims in front of the pistons, where the brake pads would normally be, then pump the brake until all the pistons make contact with the shims. Then remove one of the shims from the stack and pump the brake until the pistons make contact again. You keep repeating this procedure until all shims are removed. One little note I would like to add: If you are removing the pistons be cause one is seized. Keep the last shim in place in front of the piston which is not seized, then continue to pump the brake until the seized piston leaves the bore. I stopped when I thought both pistons were loose enough to finish removing by hand. So I removed the caliper, drained the remaining fluid from it, and took it to my basement shop to finish disassembly. As it turned out, the non-seized piston came out the last 3/16" very easily. Unfortunately, I spent about 20-minutes trying to remove the stuck same distance. You cannot use pliers to remove the pistons if you plan to reuse them, because it will damage the chrome finish, which will in turn ruin the piston seals.

Piston Removal 1.jpg
A full stack of shims at the beginning of the process. I used 1" x 1/8" aluminum to make my shims.

Piston Removal 2.jpg
After removing a couple shims part way through the piston removal process. (Note: I used a rubber band to hold the shims in place while worked)

Disassembled Caliper.jpg
Success! The caliper is finally disassembled and ready for cleaning.

Tonight I cleaned up the caliper and the pistons, and they look like they can all be reused. The biggest problem I found, and cause of piston seizure, was corrosion in the outer piston seal groove.

Bore Corrosion.jpg
Here's a close up shot of one of the piston bores, and you can see the corrosion in the seal grove.

Both piston bores had this corrosion, but only one piston has seized. This corrosion squeezes the seal tighter around the piston, which prevents it for moving in and out properly. I spent a little time using a pick tool to remove the worst of the corrosion deposits from the seal grooves. Tomorrow I will use a Dremel tool with fine brass brushes to polish them up. With a little luck the parts I ordered from Dennis Kirk will be here tomorrow afternoon as well, and if I have the time I can get the caliper back together.
 

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Discussion Starter #12
My new seals arrived yesterday afternoon, along with a few other parts I ordered from Dennis Kirk, so I spent a little time finishing up the brake caliper. I used a couple soft, brass, wire wheels in my Dremel tool finish polishing the seal grooves after removing the worst of the corrosion with a small pick. They came out looking very good.

Bore Clean.jpg

Next I coated the new seals with a little fresh brake fluid and installed them.

Seals In.jpg

I then coated the pistons and bores with brake fluid and inserted the pistons. They went in with just a little resistance.

Pistons In.jpg

Finally, I reassembled the caliper itself.

Caliper Reassembled.jpg

All that took about 30-minutes. Today I went to the local Honda dealer and picked up a couple new banjo bolt washers. I should have ordered these when I got the seal kit, or checked an automotive parts dealer first. I paid $7.50, which includes tax, for two of them! I was expecting one or two dollars each, for something which is a pretty standard expendable part. I meant to pick up a new bottle of DOT 4 brake fluid, but I forgot, and don't know if I will have time to get out later today to get it. I was planning to get the caliper installed and the brake bled tonight.
 

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Discussion Starter #13
I was hoping to get the caliper on the bike tonight, but by the time I had time it was just too cold to be messing around outside. I did get a few things done tonight such as, remove the insturment cluster and clean it, remove the top triple tree so I could remove the remains of the screw which secured the ignition. I then remounted the ignition to the tree, and used some red and white model paint to detail the lettering on the ignition switch (I was going to take a photo, but my phone was dead). Everything should be ready for me to reassemble the next time I get an hour or so of spare time.

Once that is done it will be time to drain and remove the fuel tank, followed by anything else which needs to come off, so I can remove the carbs. I'm both apprehensive and excited about rebuilding the carbs. It will be an interesting challenge, as I have never messed with a four-carb set-up before. Thankfully, I learned quite a lot from my experience tuning the dual carbs on my CL450. I also need to build or buy a multi-carb synchronizing tool. I've seen a few tutorials on how to make an inexpensive one, but I'd really like to have a nice one for future projects.
 

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Discussion Starter #14
Well it took me a lot longer to finally get back to the bike than I expected, but I think most everyone on this forum understands how that goes. I'm also finding that a sure fire way to get more paying work is to start project I enjoy working on
(I do freelance graphic design work, website content development, photography, video production, and a few other things my military journalism career gave me the skills for). As a result I've been spending most of my free time taking care of a client, and the night's I wasn't busy it was just too cold to play outside.

Tonight I finally got back to work despite an outside temperature of 32-degrees. I got the top triple tree back on, along with everything else I had taken off it. I reinstalled the front brake caliper, then reverse bled it to get the system filled up with fluid. I was getting fluid leaking from around the bleed screw during the reverse bleed, and saw air bubbles come into the clear tubing on my syringe when I would pause to check the reservoir level. Because of this I decide to do a conventional bleed as well. It was a good call as there was a little bit of air still trapped in the caliper. The front brake seems to be working good, but I still need to spray down the disk and caliper with brake cleaner, and give everything a final going over in the daylight.

Back Together.jpg
 

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Discussion Starter #15
So, tonight I thought I'd take on a simple project: Remove one of the turn signals and figure out what it will take to replace the broken stalks on all four of them. Removal was very easy, as just one nut mounts each one to the bike, then all that's left is disconnecting the wires. It only took a couple minutes outdoors, and I was off to my unheated basement, which thankfully is still about 20-degrees warmer. When I dissected the turn signal, I discovered Honda intended the signal and stalk to be a single piece part. The stalk can be separated, but doing so will ultimately ruin the signal housing. This now explains why I couldn't find individual turn signal stalks for this bike anywhere on the internet. Ultimately this is not that big of deal. Aftermarket turn signals are fairly cheap, but I have to find some that are three wire, and not the more common two wire. The signals on this bike are meant to be running lights as well as signals, and have two filament bulbs. I also want to find some with a simple OEM style look, this is a simple bike, not a flashy street racer or a chromed out cruiser. So now I'm off to visit Amazon to see what I can find before a new pile of bills shows up in the mailbox on Monday.
 

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Bike Master and Emgo offer reproduction turn signals for these old Hondas. My local Honda dealer has catalogues with them and they are not that expensive.
TOOLS
 

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I love how this thread has 17 replies for a 4cyl bike on a twins forum. I'm not complaining I just enjoy the irony. Hoping for a HD build in the future.
 

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It's the friendliest place on the internet for stuff like that. I stumbled on Jockey Journal during an internet search and read a thread about a 450 build, so I went and joined up to share mine... only to get an email afterward telling me I couldn't post my 450 build because they stopped taking non-American or British bikes a year or so before (in other words, no Japanese builds). I sent them a caustic reply and they removed my introduction post
 
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