Wednesday 30 March 2022

Honda CB750F2

1977 saw the birth of the Honda 750F2, the last UK model that had evolved out of the original, late sixties, CB750K1. All the bikes used the same basic SOHC engine that in some peculiar ways was a throwback to the abortions of British engineering, featuring, as it did, such antique items as a chain primary drive (albeit, a very strong hyvoid job that didn’t wear very quickly - just as well as a total engine strip was needed to fit a replacement) and a separate oil tank. OK, it was relatively smooth and had an electric start to aid bikers maimed by British bikes; it also tended to stay together pretty well.

As the K1 got older, it became heavier and slightly more stable. By the time the K7 arrived it was outclassed by several rival fours of superior design and power output. In a not untypical Honda manoeuvre the F1 was introduced with a new euro-style, a lot of hype and a slightly tuned motor that almost ruined Honda’s reputation for durability by self destructing with apparent ease.

The F2 had an impressive package of modifications, not least a de-tuned motor that stopped it falling apart, almost meeting the standards of durability found in their first four. Although it may not be so impressive that Honda had to make the bike go slower to be more reliable, at least the rider was ensured of some kind of peace of mind; not until the completely new CBX750 was introduced did Honda get back into the right frame of mind that produced the best bikes although tales of burnt out exhaust valves in these models does show that four valve technology is still not fully understood.

Despite the lack of ultimate top speed (down 5mph to 120mph) the F2 did feature higher lift cams, widened ports and bigger valves, which managed to produce 69hp at a mere 8500rpm. The F2 weighed in at 495lbsdry. It is the nearest that Honda came to perfecting the CB750 formula. The real cutting edge was achieved when the older motor was stuck in a decent chassis, Dresda, in particular, shaving off around 100lbs, allowing a stock motor to increase performance and maintain reliability - at the expense of an uncomfortable cafe racer riding position.

An immediate problem apparent on the F2, especially in the damp, wet riding days of the UK, is that the front brake doesn’t work in the wet. The F2 did have an extra disc fitted, which considerably improved braking in the dry. Swapping the stock pads for types specifically designed for use in wet weather made not one iota of difference. In fact, so bad did these brakes become in my mind that they stood right out from the rest of the machine which exudes a feeling of dependability. Naturally, when these very same brakes seize up their calipers the temptation to start bashing the whole affair with a large hammer is very hard to resist.

Whilst the bike is far from being a lightweight, town riding was no real hassle if you were willing to put in a bit of effort. At least the large wheels didn’t suddenly flop into slow corners like 16 inchers. Engine width was more of a constraint when flicking through cars than the actual mass of the machine. The bars are usefully wide for exerting pressure at low speeds, but a touch too high and wide for comfortable high speed cruising. On very long journeys this: can conspire with a heavy throttle and a wide seat that digs into the thighs to make things less than perfect.

Really fast hustling was rather inhibited by a speed wobble around 110mph and a shower of sparks in left-handers from the centre stand tag digging in. Changing direction in fast corners needed mucho muscle and stability went for a long walk if you jammed on the brakes when in the middle of a corner, although a bit of moderate engine braking by shutting down the throttle was a relatively safe way of losing speed.

When new, the suspension gives a ride that approaches excellence, and the suspension exhibits an uncharacteristic amount of damping effect way ahead of the sixties stuff and not that far short of the very modern components. Of course age is never kind to Japanese suspension - by the time the warranty has expired, and the better Wop stuff has just bedded in, the F2 suspension has to be fettled with, at the very least, the good old stand-by of heavier fork oil and Koni rear shocks. At least twin shocks are devoid of quick wear linkages and nasty maintenance problems.

The motor has been remarkably free of trouble, maintenance mostly a case of checking rather than actually adjusting. This is only as it should be, because by Jap standards it’s no powerhouse, but in return for a lack of excess of top end madness there’s a commendable middle range punch that makes the bike a pure joy to hustle along fast A roads.

No engine is totally free of problems, though, and the F2 will soon start giving trouble if regular oil and filter changes are neglected. Every 1000 miles would be a good starting point for oil changes. If you don’t do this, and use the bike hard, you'll end up rebuilding the whole top end. Expensive. The clutch is a little notorious for rattling and not quite as strong as it ought to be - but moderate use causes no harm. It’s also worth checking the motor on the overrun, or when changing down through the box, for white smoke out of the exhaust - a sure sign that the valve guides are on the way out - something that can happen from 20000 miles on.

A big plus in owning any CB750 is the interchangeability of the various parts of the different versions of the bike. This compensates for the extortionate cost of factory and, to a slightly lesser extent, pattern parts. Not that this was much of a hassle as the most expensive problem I had was replacing the rotted exhaust. A’ fair bit of persuasion was needed as the Motad 4-1 was really designed to fit one of the K series. It’s just that it was going cheap...

One of the problems of owning a bike with an engine designed ten years before the current noise and exhaust legislation is that the engine is adapted rather than designed with these constraints in mind - thus fuel consumption could be a pretty frightening 35mpg, although it did average 50mpg and even did a best of 65mpg on occasion. By way of compensation, the oil consumption was negligible.

The drive chain was an endless O-ring job that lasted for a reasonable 15000 miles, with a slight adjustment every 4000 miles. The points never needed much in the way of adjustment but oxidized badly during winter lay-ups and were replaced each year. The original Jap tyres were replaced by Roadrunners that lasted slightly longer than the Japs - only 5000 miles on the rear but 15000 on the front.

The F2 doesn’t come fitted with a kickstart and when the battery goes dead it’s a very heavy bike to push start. Also the silver in the headlamp faded to such an extent that night-time riding became very dangerous - it was cheaper to fit a pair of bolt on spots than buy a Honda unit! The speedo was wildly optimistic - an indicated 140mph was really only 120-125mph!

These are minor quibbles, on the whole the bike was a great all-rounder, dependable almost to the point of boredom. Not exactly a plodder, but then not really a scratcher either. A good bike for touring. Less weight, proper front brakes and a little bit more power would have made it a real winner.

Ginge