Honda CB450's have had a mixed press. Some of this based on ignorance, some based on the variable quality of the machines that have survived and the rest down to the idiosyncratic nature of the beast. In the mid sixties it was certainly state of art, compared to the vibratory, unreliable and oily British twins. It also revved to heights that would've left your average British twin a pile of wreckage.
Its chassis was standard fare for the era, conventional more in a European sense than Japanese, whose machines up until then had been rather oddly styled with the possible exception of the CB72/77 Dreams, which were the first Hondas to edge away from a shape that was defined by sharp angles and squareness. In fact, in the early sixties most people bought Hondas because they were different.
The DOHC motor defined the design. In the mid sixties engines that wanted to rev to 11000rpm basically didn't exist in large vertical twin capacities, due to valve float. Honda's way around this was to throw away conventional valve springs, replacing them with torsion bars. As these were operated via rockers that also lowered the effective mass of the valve-train. Just to be awkward, the camshaft lobes acted on another set of rockers which in turn operated the valves. The clever part being that the rockers themselves were set on eccentric shafts that could be rotated to alter the valve clearances.
All that added up to a lot of mass held high and an excess of precision machining, the tolerances so fine that matched sets of valve-gear were fitted. So expensive that it was never repeated in any other Honda model, save for the stroked CB500T, where production engineering economies meant it never matched the success of the earlier 450cc version and often died an early, not entirely unexpected, death.
A lot of people had bad experiences with secondhand Black Bombers, most of that down to two things. Engines where the valve-gear had been mixed up and thus mismatched. And people who insisted on revving the engine harshly from cold before the motor had a chance to circulate sufficient oil to the top end. Either could prove disastrously expensive and turn a bike that was basically well designed and reliable into a liability.
Considering that some bikes are nearly 35 years old, and that the most recent CB450 is a quarter of a century babe, the few bikes still on offer on the secondhand market are very variable, both in price, originality and quality. The Japanese classic brigade also distort things a little but have never really managed to define the market; those who demand British-bike style prices usually end up waiting years to find a buyer. Pay silly money, chances are you will never get it back.
The early model had the classic rounded styling, 43hp (at 8500rpm) motor and four speed gearbox. The later bikes had an extra ratio and two more horses but lacked the edgy power delivery of the earlier model, which true to many Honda ranges defined the classic status of the breed. The 43 horses at 8500rpm a bit misleading because it didn't stop the engine revving to way beyond 10,000rpm, those of an adventurous disposition able to hit twelve grand in second! No way to treat what is now a venerable classic .
That added up to an easy 90mph cruising pace in fourth gear, with another 20mph in hand for putting cagers in their place, though ton-plus performance was dependent on external conditions and the rider's willingness to kiss the cute combined tacho/speedometer.
Because the pistons moved up and down alternatively there wasn't any primary vibration but a fairly strong torque reaction along the crankshaft, mostly manifested in low rev shakes. With the 5000rpm plus power outpouring came much improved smoothness, way beyond what British twins of the era could muster.
The relative roughness at lower revs was probably off-putting to people who test rode the bike, expecting things to get worse at higher revs rather than better. The tall, top heavy motor also failed to instill the feeling so prevalent amongst British twins of instant security, though it also lacked the inherent terrors of many later Jap bikes (Kawasaki triples, XS-2, etc). A retail price not far off that of a 650 Bonnie, then considered prime meat, added to the likelihood that the punters would look elsewhere. Honda had the CB750 four to come, which would eclipse the purity of the earlier vertical twin's engineering.
By modern standards, compared to, say, a new Honda CB500N, the 450 feels incredibly rough, more like someone had fitted a diesel lawn-mower engine into a rough approximation of a motorcycle frame. Vibration, finicky controls, suspension that lets through every road bump and a riding position that combines forward pegs with narrow, rumbling bars.
Ride the Honda for a little while, most of the intrusions gradually fade into the background; swapping back to a modern bike makes the latter feel sensationally smooth and sophisticated. Any bike with any amount of mileage on it will have a pretty nasty clutch and gearbox. The former has an excess of drag in town riding, the latter is just plain poorly designed once some wear gets to the selectors. Those used to sixties Hondas will know the score, newcomers will learn some new curses! Call it a learning experience, the box can be mastered eventually.
On the gearbox, one particular trick is for the clutch pushrod to start leaking oil. This is situated right next to the final drive sprocket - if the chain breaks it hammers the pushrod which in turn ruins the oil seal, although the seal can just wear because of all the debris thrown off the chain on to the pushrod.
Honda eventually changed the clutch design but not until the late seventies. Actually, if the chain breaks it can whiplash the back of the engine crankcase, some clowns repairing the cracks with Plastic Metal which then falls out! Even welding is a bit dubious as it can distort the crankcase, leading to all kinds of interesting internal problems.
Either this or the leaking pushrod seal can drain the engine of lubricant with disastrous consequences. Because there are lots of roller bearings in the bottom end, it can run until the last drop of oil's disappeared - by which time the whole top end is most definitely dead.
There are a couple of other things to look out for on the lubrication front. As the engine ages the oilways can gum up, restricting the amount of lube that circulates. There's also a gauze filter tucked away behind the rotary oil pump that also gums up if totally neglected (you need a special tool to get to it so it's very rarely done even during fairly major engine strips).
Oil changes need to be done every 500 miles even when using the best quality 10/40W lube. An early warning sign of trouble comes from the magnetic sump plug picking up metal debris! 500 miles also means a full service - valve clearances (an annoying amount of precision needed), points' gap, ignition timing, carb balance (can be done by ear) and camchain tensioner tweak (weak bolt that can strip its thread).
Neglect all this maintenance hassle, performance drops and vibes increase, though it doesn't do much damage to the motor until the valves tighten up and burn out (takes about 5000 miles).
Generally, these are tough engines that thrive on revs and even abuse, even at their great age. I know some rider's who treat them with kid's gloves, actually ride mostly in the lower rev range, which gives out the most vibration - surely not very good for the engine? No, they definitely need a bit of stick.
Unlike most British Iron of the same era, they are actually up to modern motorway speeds. Well, as long as you put some time, effort and money into upgrading the chassis. At 410lbs it was a bit heavier than rival Brits but that heftiness is readily apparent in things like the steel mudguards and seat base. It takes an awful lot of time to rust them to a state where they can't be salvaged.
The frame is strong, the geometry fine once used to the slightly top heavy feel. The suspension wasn't firm from new but doesn't wear that badly with age. The rear shocks the most obvious area of concern. Girlings go down well (but go for heftier ones than specified as they are supposed to fit the much lighter CB350K's as well and don't exactly transform the bigger twin).
The front end's a bit of a mixture. The TLS front brake good for a couple of fierce stops a day, can twist up the forks, but then it starts to fade a little. There are any number of ways to improve the forks but the effort probably isn't worth it, compared to a hit on the breakers where a relatively modern front end can be found. Hard to find anything worse than stock.
Thus equipped, aided and abetted by some modern(ish) Avons, the CB450 can be slung around as well as the latest CB500 twin. Perhaps not much of a compliment but that's Honda own fault for failing to be leading edge, any more, in vertical twin design. More shame on them as in every sense they invented the modern breed back in the sixties.
Interesting performance, adequate handling, easily modded riding position to suit the rider's taste (the OE saddle more comfy than many minimal modern efforts) and an engine that shouts character in the same way as those hordes of classic Brit's, without most of their mechanical infidelity. Add in prices that are much more realistic than the classic British stuff.
Conclusion: don't be put off by the initial riding impressions, make sure the engine is mechanically quiet (amazingly so at the 800rpm tickover) and if you find one that is in good fettle go for it. But bear in mind that spares are both rare and expensive, and that the motors can turn finicky if they have been long neglected.
Terry Davis