From our Old Bike Archives – Issue 84 – first published in 2019.
Story and photos: Jim Scaysbrook
Sometimes being ordinary can be a good thing. In the case of Honda’s CB350, a very good thing.
Figures vary, but in the period of the little twin’s existence, from 1968 to 1973, more than 300,000 were sold, and for a while it was the top selling motorcycle of any capacity in the booming USA market. Add to that figure a hefty number of the street scrambler CL350 and you have a success story that today could only be dreamed of.
At this stage, Honda were extremely adept at making what the market really wanted; relatively simple, utterly reliable, clean running four stroke singles and twins – from 50cc step throughs to the sophisticated DOHC CB450. The CB350, and its near identical sibling CB250, were the generational leap from the earlier CB72/77 twins, and in outright performance terms, roughly identical. But the CB250/350 was more sophisticated, less sporty, and more appealing to the masses who were discovering motorcycling as a cool means of transport.
At the heart of the matter was a parallel twin engine with the cylinders vertical, as opposed to the CB72/77 series which had the cylinder sloping forward. Up top sat the familiar chain-driven single overhead camshaft running two valves per cylinder set at an included angle of 66 degrees, and down below was a 180-degree pressed-up crank. Actual capacity was not 350cc but 325.6cc, achieved by a bore and stroke of 64mm x 50.6mm. Stated horsepower was a relatively modest 36hp – but which was substantially up on the 28.5hp produced by the 305cc CB77. And there was an extra gear in the box over the 72/77 four-speeders, which had somehow been squeezed in to the existing cluster. This made a significant difference to the ‘rideability’ of the new model – removing the yawning gap between first and second gear that had taxed acceleration, and which also made down-changing to first gear quite a chore.
A close look at the engine revealed that there were indeed many differences to the 77, some subtle, some major. The camshaft now sat in aluminium caps at either end, not the old ball races, with no centre bearing, and with rocker arms on externally adjustable eccentric spindles, similar to the DOHC CB450. Driven from the centre by an endless chain, the camshaft sprocket had bonded rubber resonance dampers to reduce chain noise, with a slipper tensioner between the cylinders. The dual valve springs were new: progressively wound to cope with the +10,000 rpm capabilities of the new engine, yet providing modest seat pressure. The inlet ports stepped down from the 32mm carb venturis and progressed around the valve guides in an ‘hourglass’ configuration to accelerate the mixture intake and cylinder filling.
Four main bearings supported the crankshaft; ball bearings on the drive side and rollers for the others, with the crankpins running on roller bearings. The left side of the crank drove a 100 watt generator and the starter motor. In keeping with its drive to a new, less sophisticated (in motorcycle terms) market, Honda paid meticulous attention to balance, and hence smoothness. The new 350 scored maximum points in that respect, being virtually vibration-free. Primary transmission had also been redesigned to give more efficient meshing without increasing the gear sizes. This was achieved by using two rows of gears, the teeth of one row staggered in relation to the teeth on the second row. The power is transferred to two rows of teeth on the clutch drum, meaning that the time the gears are in mesh is doubled, and avoiding the power losses associated with a more inherently silent-running helical gear. Speaking of the clutch, this was a hefty affair with eight metal and eight friction plates and a four-spring pressure plate, running in oil, and apparently bullet-proof. Although Honda had used constant-velocity Keihin carbs before, those fitted to the CB350 were of a more refined design, with a new jet system to improve low-speed running, as employed on the CB450.
Chassis-wise the CB350 was fairly conventional, with pressed and spot-welded sections rather than tubular steel in most places except the swinging arm and the front down tube and engine cradle – which after all were the most visible parts. A large section welded-up pressed steel backbone anchored the frame, with pressed gussets holding things in place. In most respects, the frame resembled a slimmed down version of the CB450 chassis, with a heavily reinforced steering head and a double cradle loop at the bottom. To further ameliorate vibration, the top engine/frame mounts contained rubber buffers. In fact rubber mounts were in abundance; for the petrol tank mounts, tail light, rear mudguard, handlebars, ignition switch and elsewhere, including the carburettor mounts.
Exhaust pipes were twin-skinned, with large diameter chrome plated outers enclosing smaller inner pipes. This not only reduced the tendency for discolouration, but the smaller diameter inner pipes increased gas velocity at the lower end of the rev range. The pipes finished in rather pleasant looking reverse cone megaphone that emitted the characteristic Honda crackle from the 180-degree firing order.
In terms of suspension, the CB350 broke no new ground, with conventional (one-way damped) Showa units up front and gas-filled twin shocks at the rear – the back end being particularly spongy despite having 3-way preload adjustment, and somewhat below par. Surprisingly, given their dimensions and quality look, the brakes were generally criticised in road tests as being inadequate; the rear would lock fairly easily while the front would refuse to do so under any circumstances and give a rather lazy approach to retardation. Another point of rancour was the fact that the seat was not lockable, and nor was the tool box, giving felons easy access to the tool kit, which realistically, should have been located under a lockable seat.
The new CB350 was certainly a breath of fresh air, styling-wise, when it hit dealers’ showrooms in 1968. Gone were the old slab-sided, chrome panel tanks and in came two-tone décor in white with either red or turquoise contrasting panels. Also gone was the traditional system of mounting the speedometer and other instruments within the headlight shell. Speedo and tacho were now separate and mounted on a bracket above the headlight, but the ignition switch still resided under the left hand edge of the fuel tank, instead of between the instruments, where it logically belonged. Front brake and clutch cables routed neatly through a curved bracket attached to the handlebar mounts.
Generally sold as the Super Sport, the CB350 went through several styling changes over its five-year production run. The first deliveries in 1968 had rubber knee pads on the tanks, similar to the 72/77, but these were quickly dropped. The first real change came in 1971 when the basically white colour scheme gave way to either candy gold, red or turquoise, with a black swirl on the petrol tank – a style that later appeared on the Wankel-engined DKW. Now that made a change: Europeans imitating Japanese. The 1972 model also dispensed with metal for the side covers in favour of plastic, which was also used for the rear chain guard, air filter box and headlight shell. Towards the end of the production run in 1973, some markets received the CB350 with a single disc front brake.
In Australia, the CB250 – virtually identical to its bigger brother in every respect except the bore size and the final-drive ratio – outsold the CB350 by a considerable margin. In 1972, the 250 was only $52 cheaper, but in its largest market, New South Wales, the 350 was slugged with crippling registration fees; the same fee applied to the CB750 for example, while bikes of 250cc and below enjoyed a much lower rate. This was indeed a pity because the 350, despite only having a 4-horsepower increase, offered much more robust performance across the rev range. It may also explain why NSW dealers’ workshops absorbed a surprising amount of the CB350 pistons, which were 8mm larger than the 250 and, thanks to the substantial thickness of the cylinder sleeves, went straight in after a rebore.
When Honda, or market forces, decreed that the CB350’s time was up, its replacement in 1974 was the six-speed CB360, described by one road tester as “about as characterless as a real motorcycle can get.” The extra capacity (actually 356cc) was achieved by taking the bore out to 67mm, while retaining the 50.6mm stroke, which begs the question, why did Honda refuse to take the CB350 from 325cc to a full 350; what would appear to be a relatively simple modification that dealers and customers had clamoured for since its inception. The unloved CB360 was heavier (168kg wet), less powerful (34hp at 9,500 rpm) and slower than the model it replaced, but fortunately for Honda, it had the brilliant CB400/4 in the wings.
Unlike USA, the ‘street scrambler’ CL350 never enjoyed a major market share in Australia, for reasons probably dominated by styling. At 33 hp, power was down on the CB350, and weight up, largely due to the massive exhaust system. However out here, because of the volume sales of the CB250/350, good tidy examples are not that hard to find, and spares are plentiful and reasonably priced. And these days, with Historic registration, those annual registration fees that retarded sales of the CB350 fifty years ago are a thing of the past.
Restoring a CB350
The featured motorcycle here is owned by former motorcycle dealer, race tuner and now restorer Steve Ashkenazi, who has had the bike “laying around in boxes” for around ten years. Steve recalls that he was wandering around the various sites at the Gatton Swap Meet in Queensland when he spotted the bike, which was originally in the gold/black decor.
“I had one of these back in the day, a 1969 model, one of the original white models, but a 250 because you couldn’t afford the stupid registration fee they (in NSW) wanted for a 350. I used to thrash it around as a kid, used to double (wife) Wilma to the (Sydney Showground) speedway every Saturday night and rode it to work every day of the week. Anyway, I saw this one just sitting there, unmolested, complete, even all the crankcase screws were completely unmarked, I just re-zinced them for the restoration. That’s what attracted me to it; it was just so original, 23,000 miles, although it looked pretty crap. Apart from things like instruments and the mufflers, I’ve reused all the parts. It ran too – ran like a clock and ticked over nicely – the only reason I really pulled the motor down was I thought the cam rollers were fifty years old, the rubber goes hard and can chunk. But the bore was like new, I just honed it, put in a set of rings and the cam tensioner rollers, that was it. I just vapour blasted the cylinders but the motor was like new; one of the easiest bikes I’ve restored.”
Visually, the CB350 is stunning, the paintwork done by Sam Muldoon (trading as Colourfuel), formerly from Bathurst and now at Taren Point, Caringbah, not far from Steve in southern Sydney. “I gave him a colour match for the paint, supplied the graphics, he did the frame and all the black bits, and I think the result it excellent.”
In the decade he has owned the CB350, it has simply been stored awaiting attention, and Steve has kept an eye out for the few parts that were needed. “I used the original header pipes and got a set of mufflers from David Silver in England; they’re pretty good although the seams look a little bit wide to me, but I don’t think anyone will notice. And I found a set of instruments in the States which weren’t expensive because of the exchange rate back then, so I just grabbed them and put them away. The only other change from standard is the ignition, which is a Pazon from New Zealand. Again, I have had this for years so I thought I may as well use it rather than the points.”
Steve and Wilma are serious rally goers and their bikes are always ridden hard, and despite being only 325cc, the CB350 performs very well. Around the city, the flexible engine and five-speed gearbox are a great combination. The CB350, like several others in the Ashkenazi stable, is fitted with a Ventura Evo rack and bag which is large enough to swallow just about everything you’ll need for a day out.
“Since I’ve been riding it,” concludes Steve, “I’ve come to think that as I get a bit older, a lighter weight bike like this could be just about ideal. It’s got enough power, and is a lot easier to manoeuvre than some of my other bikes.”
Specifications: Honda CB350 1972
Engine: SOHC parallel twin with 2 valves per cylinder. Air cooled.
Bore x stroke: 64 x 50.6mm
Capacity: 325cc
Compression ratio: 9.5:1
Carbs: 2 x Keihin CV 32mm
Ignition: Coils and battery
Starting: electric or kick
Power: 36hp at 10,500 rpm
Transmission: 5 speed, chain final drive.
Suspension: Telescopic front forks 117mm travel, swinging arm rear 73mm travel.
Brakes: 180mm 2LS front, 160mm sls rear
Tyres: Front: 3,00 x 18, Rear: 3.50 x 18
Wheelbase: 1300mm
Dry weight: 149 kg
Fuel capacity: 15.7 litres
Top speed: 171 km/h
Price (1972): $806.00
