Honda dropped the NightHawk in fall 1969, and the moto-market scrambled to figure out what just hit ‘em.
The NightHawk sometimes referred to as the CB750, had the first inline four-cylinder motorcycle motor to roast at high RPMs.
Honda had set the industry bar; there was a new way to build motorcycles.
The Honda NightHawk CB750 remained popular throughout the 70s up to the 90s, and there is a slew of used NightHawks available, but what are the common problems with these motorcycles?
Set your side stand down, and read on to find out!
1. Charging System Shaft Chain Breaks
As we mentioned earlier, when the Honda NightHawk came out, it changed the game.
The NightHawk was one of Honda’s first inline-four-cylinder motorcycle engines.
Honda achieved its unique and advanced engineering by moving the starter and Regulator/Rectifier onto a hidden shaft toward the rear of the motor to keep the inline motor narrow and sleek.
Simply put, the stator charges the NightHawk’s battery by converting RPMs into power using a chain on this discrete shaft.
The power the stator pulls from the bike is DC; since batteries require an AC charging current, the DC passes through a component called the Regulator/Rectifier to convert the DC into AC, rectifying the situation.
The NightHawk’s R/R also regulates the charge the battery receives, cutting it off or draining the battery as needed to prevent it from overcharging or exploding.
That chain on the hidden shaft on which the stator and R/R rest are where our problem lies.
Both original chains connected this hidden shaft from the crankshaft, and the chain tensioner was known to break.
Honda developed an upgraded chain to fix this problem, but not until after 1985. For any owners of those early Nighthawks plagued by this problem, here are the symptoms of a broken charging system shaft chain on a Honda NightHawk:
- Battery won’t charge
- Dysfunctional stator
- Poor idling
- Power loss
- Dead battery
It’s not a simple fix, but many pro-Honda mechanics are aware of the situation.
A decent, 80s Honda-literate mechanic will be able to pop out your motor and replace the failing chain and chain tensioner with the upgraded one Honda designed to remedy the failure.
It’s important to note that, while this is a known issue, in some cases of charging system shaft chain failure we came across, the Honda NightHawk in question hadn’t been ridden regularly or stored properly by its previous owners.
2. Oil Leaks Into the Starter Motor
We’ve encountered multiple Honda NightHawk owners who say that their starter had various problems, but only a few of those owners figure out the issue based on the following symptoms:
- Nighthawk has trouble starting
- Oil in the starter motor, often leaking back out.
- Imbalanced starter commuter shaft
- Worn brushes
Let’s work backward to try and pinpoint what’s happening in there.
Leaky rings cause high compression in the crankcase. This, combined with the imbalance starter commuter, lets oil into the starter motor, although replacing the seals in the starter motor case will keep the oil from leaking out of the starter motor.
If the commuter shaft gets out of balance, it will wear out your brushes early.
These worn brushes allow the oil to leak into the starter motor if crankcase compression gets high enough.
Replacing the brushes and brush holder is a cheap fix, fortunately, and it’s a fix that prevents the problem from happening again for quite a long time.
More than a few NightHawk riders in the forums expressed their frustration when they heard the problem; the problem often gets misdiagnosed, and the starter remains problematic.
Sometimes, even after you replace the brushes, the starter is still exciting up. This is generally due to the motor’s damage from the oil leak before you replaced the brushes. If your starter has had problems for a significant amount of time, buy a new or rebuilt starter that fits your NightHawk and start from scratch.
Swap your old dog starter out for a fresh new pup, and your bike will bark to life as soon as you push on it.
Some say the cause of the oil leak is a defective oil seal on the main bearing. It’s not a bad idea to replace the bearing when you replace the starter to be on the safe side.
The bearing seal’s wear could be caused by faulty alignment, though, so have a mechanic look the whole situation over so it doesn’t continue to happen.
3. Transmission Pops Out of Gear
According to multiple NightHawk riders, the motorcycle can develop a gearbox problem that causes the bike to pop out of gear.
From what we’ve read, these riders will notice the issue in second gear initially, but eventually, the gear-knock will happen in third and fourth gears too.
So, what’s the culprit in the gearbox problem on a Honda NightHawk?
There’s a component inside the Nighthawk’s left-most shifting fork (out of three). This small transmission piece wasn’t sized right at the factory, and once it wears out, and when it does, the bike will skip a gear.
We’re told that the issue is most prevalent when riders shift their bikes from first gear to second.
We want to note that this issue is apparently avoidable, provided the Honda NightHawk rider shifts firmly and with intent.
4. Speedometer and Tachometer Needles Break Off
One complaint we’ve heard from owners of old Honda NightHawks is that the needles on the instruments, namely the tachometer and the speedometer, will break off.
This makes the gauge more difficult to read, but many NightHawk riders say that you can still read the instruments enough to know your roundabout speed and RPMs.
But why do the instrument needles on a Honda NightHawk break off so easily?
Sunlight penetrating the instrument gauge’s glass is magnified. In time, repeat exposure can degrade the plastic needle of the instrument, eventually causing them to break. The surface of the gauge discolors with age due to repeated sun exposure, making it hard to read with or without a full-length needle on deck.
This isn’t necessarily a testament to a design flaw. The fact is that Honda makes reliable motors—the engine of a NightHawk from the early 80s will far outlive some of the small, plastic, cheap components.
If you’ve experienced degrading instrument needles on your NightHawk, stock replacements may be hard to come by at this point.
Most NightHawk riders we’ve heard from on this were forced to fab their own gauge displays, either from those intended to fit other models or from scratch.
5. Clutch on Used Models Worn From Old Age
One of the common complaints we encountered about the NightHawk isn’t exactly a problem or flaw; the expected reality when buying a motorcycle, like the Honda NightHawk, that’s over 30 years old, is that the clutch is often worn. A worn clutch can fail shortly after the buyer puts some miles on the bike’s clock.
One solution is to take extra care to inspect the clutch of the used NightHawk before you buy it, if only via a thorough test ride.
Another solution is to ask for a lower price and replace the clutch yourself or have it replaced by a Honda mechanic before you stack a bunch of miles onto the motorcycle’s odometer.
A worn clutch feels and sounds like a big deal, but it’s actually a pretty straightforward job.
Here’s how to change the clutch on a Honda NightHawk:
- Pop the cover off one side. You may have to remove the brake pedal to get to it, but not much else.
- Once you’ve pulled the side cover off, you’ll see six or so obvious bolts, each on their own spring. Put your NightHawk in gear to keep the clutch from spinning while you uninstall these bolts.
- Uninstall the clutch disks.
- Install the replacement disks, coating each disk with the Honda recommended motor oil as you install them.
- With the bike still in gear, reinstall the bolts. Note: we recommend replacing the springs with freshies, as clutch springs lose tension often enough as it is.
General Pros and Cons of Honda NightHawks
Here are general pros and cons of the Honda NightHawk:
Here are some of the NightHawk’s selling points:
The Honda NightHawk is mounted with an air-cooled 747cc powerhouse of an inline four-cylinder motor, a design they haven’t changed much but to improve upon.
Modern NightHawks run four-valves per cylinder, flashing its black finish and polished accents and thumping your chest with a four-to-two exhaust set-up as it rips past.
The old-school NightHawks had bicycle-style spokes that fit the era with a shine, while the modern Hawk flies on polished five-spoke mags.
The NightHawk is a streamlined machine, minimal with chrome and aluminum, polished; a black chassis to turn it minimal look to stealth.
- Charging System Shaft Chain Breaks
- Oil Leaks into the Starter Motor
- Transmission Pops Out of Gear
- Speedometer and Tachometer Needles Break Off
- Clutch on Used Models worn from Old Age
What Do the Reviews Say?
Once warmed and rolling, the machine feels very quick and light, masking its just-under 500-pound weight. The nimble handling is neutral – the bike neither falls into turns nor stays straight up. Rider input is followed precisely.
The four-banger finds its peak power in the high rpm range, as expected, with only a mild amount of buzz filtering through. Roll-on power is somewhat spiritless unless you drop a gear – or two or three – to get the revs up where they’ll do you some good. That seems to be in the 7,000 neighborhood on the tach; then the engine pulls hard up to the 8,500 RPM redline.
I found myself double-shifting the close-ratio transmission a lot around the city. But once free of traffic, I found the transmission quite useful in keeping the engine spinning up where the power lives. Down low, around 4,000 rpm or less, the bike still chugs along happy as a clam. As a matter of fact, the engine still pushes you along in top gear as low as 15 mph. Just don’t expect to move out too quickly from there.
Instrumentation is sparse, with a speedometer, tachometer, and a row of simple warning lights. The on-board clock is located on your wrist. It’s simplicity, and that’s the definition of a standard motorcycle.
The Nighthawk is a very capable machine perfect for those not really committed to a particular type of ride. Throw some bags on and a windshield and you’ve got a tourer. Lower the bars, add a small fork-mounted fairing, and you’ve got a sportbike. Or leave the machine as it is and enjoy its elementary purpose – two wheels and a motor and the wind in your face.
What Is the Resale Value of the Honda NightHawk?