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1974 Honda CB750 K4 Review
JUST Bikes 26/12/2011
When it made its debut in 1969, Honda’s CB750 four set the template for just about every large capacity motorcycle that followed. The CB 750 arguably also put the final nail in the coffin of the British motorcycle industry, as it accomplished everything the big British twins and singles did, but was more refined, reliable, better-equipped and generally cheaper. A hit around the world, the CB750 enjoyed particular success in the USA, where demand led to a number of developments over the CB750’s lifespan.
These changes were identified by ‘K’ suffixes to the model name. ‘K0’ is the somewhat mythical progenitor of the widespread ‘K1’ and ‘K2’ versions that followed. The K2 lingered in UK, Australia and some European markets throughout the 1970s, but the USA received specific CB 750 variants, the first of which, the ‘K3’, was released in 1973, followed by the ‘K4’ in 1974. Each version received refinements aimed at improving reliability and safety. US government regulations regarding safety and noise were behind a number of the changes made.
The engine in the 1974 CB 750 K4 was virtually unaltered from its 1969 debut. Certainly the capacity was the same at 736cc, as were the bore, stroke and compression ratio figures, although some markets appear to have received CB 750s with a 9.2:1 compression ratio instead of the standard 9.0:1, with gearing differing in some markets, too. The quartet of Keihin 28mm carbs was as per the original. Minor upgrades, like a revision to the cylinder head’s fin bracing, were added, which is an easy visual way to pick a K4 from a K3. On the K3, the cylinder head finning is braced by four vertical pillars on each side – two at the corners, and two on the side of the engine. On the K4, the two side pillars were replaced by a single, centrally-mounted one. These pillars, while seemingly insignificant, did perform an important function in reducing engine vibration and noise.
Less obvious engine changes included a redesigned O ring seal for the oil passage between the block and cylinder head to prevent leaks from the head gasket. During the K4’s production run, a similar improvement was made to several of the stud holes between each cylinder, again with the aim of reducing oil leaks. This upgrade aside, most of the running gear was kept as per the CB 750 K3, which had introduced several improvements over the K2. A visual addition to the gearbox was the casting into the transmission outer case of the gear shift pattern.
One interesting feature still to be found on the K4 was a friction control for the throttle. This allowed revs to remain up when the hand was taken off the throttle – a feature originally included to allow the rider to use hand signals on bikes without indicator lights. The preponderance of indicators, and the reliability of Japanese electrics, meant that hand signals were a thing of the past by the mid 1970s, so the K4 was the last model of CB 750 to retain this feature. Another ‘flaw’, if you could call it that, was the placement of the fuel tap on the right hand side of the tank. This made switching from ‘on’ to ‘reserve’ difficult to do on the run.
Visually, the seat was mildly redesigned, and the colour range was altered for 1974. Buyers could choose from ‘Freedom Green’ metallic, ‘Boss Maroon’ metallic and ‘Sunrise Orange’ metalflake. The green and maroon colours replaced the very 1970s ‘Candy Bacchus Olive’ and ‘Maxim Brown’ metallic from 1973. While these three were the officially released colours for 1974, it’s not unusual to see K4s in other colours, as rebuilds and restorations have led to older and newer colours being applied. On the tank, the black central section that housed the ‘HONDA’ badge was as per the K3, but the spacing on the black/white/gold surround to this black panel was slightly modified, with the white stripe surround being marginally larger. Side covers were colour-matched to the tank, while the badges retained the distinctive script ‘F’ with small Honda wing logo beneath that had debuted with the K1 model.
On the dials, the increments on the speedometer were changed from 20mph to 10mph with the K4, but the rest of the dash layout was unaltered. Indicators and reflector placement varied between markets, with US models generally having larger indicators and side reflectors than European market versions. Higher, ‘Western’ style handlebars were popular in America, although lower, flatter handlebars are not uncommon. While the flatter ’bars arguably look better, there’s not much difference in terms of rider control, and it really comes down to a matter of personal preference.
In terms of handling, performance and rider comfort, later CB 750s like the K4 are a comfortable and enjoyable bike to ride, if perhaps a little less ‘sharp’ than the earlier models. This is largely due to a reduced air intake aperture. Designed primarily to meet US noise restrictions, this made the CB 750 quieter, but also a little slower. The seat height – at 838mm – is a challenge for short riders, while the ‘wide’ footpeg placement also takes a little getting used to. Overall, the CB 750 should meet the needs of most riders who understand they’re not throwing their leg over the latest Fireblade, and ride accordingly.
Hugely popular when new, the CB 750 has been one of Honda’s most enduring models, lasting into the early 1980s with a DOHC engine. While the sportier ‘F’ Series CB750 Super Sports released in 1975 as a response to Kawasaki’s Z1 are a prime target for collectors today, the K Series are still incredibly popular, boasting owners’ clubs around the world, either devoted to all SOHC Honda Fours, or exclusively to the CB 750. This means plenty of advice and spare parts support for the potential CB 750 owner. For the ‘first time’ classic Japanese motorcycle buyer, a mid-1970s CB 750 like the ’74 K4 is a tourer/commuter that’s pretty hard to beat.
SPECIFICATIONS – 1974 Honda CB 750 K4
Engine: 736cc SOHC four-stroke transverse parallel 4-cylinder
Bore/Stroke: 61 x 63mm
Power/Torque: 67bhp @ 8000rpm / 44ft/lb @ 8000rpm
Fuel System: Four 28mm Keihin carbs
Cooling System: Air
Electrical System: 12 volt
Transmission/Drive: 5 speed manual/chain drive
Front Suspension: Telescopic forks
Rear Suspension: Swingarm with 5-way adjustable twin coilover shocks
Front Brake: Single 11.7 inch (296mm) disc
Rear Brake: 7.1 inch (180mm) single leading shoe drum
Front Tyre: 3.25 x 19 inch
Rear Tyre: 4.00 x 18 inch
Weight: 227kg (dry)
Seat Height: 838mm
Fuel Capacity: 4.5 US gal (17 ltr)
Top Speed: 180 kph (approx)