I took a lot or ribbing when I bought my Honda CB650. My mates all rode highly modified seventies superbikes with fearsome exhausts and thunderous power. You know the kind of thing, hopped up CB750s, turbocharged Z1's and the odd GS750 with a race-spec engine. If all this seems a little strange in 1994, when there are an excess of nice retros available, well the old superbikes, once their chassis were modified, could be continually recycled and improved. There was just no need to buy something newer.
I had one of the first CB650s, a 1979 model with only one owner and 18000 miles. In many ways a dream buy as it had only cost £750 and was in very nice shape. With just 63 horses to overcome 450lbs the only problem was that the Honda was a bit lost amidst my friends who loved to wheelie and wheelspin themselves into oblivion. Acceleration could best be described as stately, even intense use of the throttle failed to provide much of a kick in the pants, although the engine took on a harder edge once 6500 revs were up.
Various so-called friends who reckoned themselves ace tuners offered all kinds of solutions to the paucity of performance but I settled for a used Motad 4-1 and K&N filter. These fitted without any undue hassle and didn't need any carb changes except for a bit of twirling of the pilot jets. It was an ideal moment to balance the carbs so a mate with vacuum gauges was summoned. The valves were all in perfect adjustment, there were only eight of them to check and just a single camshaft. The engine design harks back to Honda's second four, the CB500/4, which shared much engineering with the original CB750. The biggest difference is the wet sump on the smaller fours, although all the bits on the 650 share more with being an uprated 500 than a downgraded 750.
I immediately fell in love with the exhaust note, a muted throb below 7000 revs, thereafter a harsh wail. People sing the praises of twins and triples but I think the sound that a four makes on cam is the business. The motor was freer flowing, happier both to plod along at low revs and snarl all the way past ten grand. It still didn't have a hope against the other bikes but I was enjoying myself playing tunes on the engine, and that's what counts, ain't it?
The gearbox could've been better, though, there was a tendency to shoot straight past the gear required into a false neutral. By the time I'd located a working gear it was usually one or two ratios taller than I expected. A lot of the time I preferred to leave it in fourth, which would go down to 20mph and up to 90mph, a brilliantly usable range of power.
Top speed was 120mph, but it was accompanied by such secondary vibes that I was dissuaded from holding it for too long. Anything up to the ton, though, was permissible. However, the engine always had a revvy feel, even when cruising in top I was looking for another gear or two. When, after 4000 miles, the chain and sprockets were due for replacement, the chain needing 150 mile adjustments, I decided it was a good time to change the final drive ratios.
A gearbox sprocket one tooth bigger and a rear wheel sprocket four teeth smaller would give 15% taller gearing. I checked this out by taking off in second and third with the old gearing, encountering no problems. It's pretty pathetic really, that most modern bikes are geared to produce startling quarter mile times rather than for the benefit of the rider.
The whole feel of the Honda was changed radically. A deeper exhaust note and much more relaxed feel did not mean slower acceleration as it would take off in first and hit 50mph before needing to change up. The new chain had also smoothed out some of the nastiness of the gearbox, which was much less needed in town, rarely getting out of second.
100mph cruising was wonderfully relaxed, although top gear wasn't much use below 50mph. Obviously, the lower revving engine meant less wear and reduced levels of secondary vibration. Also, fuel went from a terrible 35 to 40mpg to over 50mpg. Out of interest, I cruised the bike for a couple of hours at 70 to 75mph, which was just tolerable in the slow lane, getting 62mpg for my pains. By no means exceptional, but tolerable for long distance cruising.
A lot has been written about how seventies muscle bikes handled, or rather how they don't. The CB650 was somewhere between the extreme of early seventies stuff and the implacable stability of later eighties bikes. Honda had gained sufficient knowledge of steering geometry and weight distribution not to produce a complete turkey. By the time the CB came into my hands, the suspension was worn out and some of the bearings were on the way out. The result was some quite large weaves but no nasty wobbles, which suggested the tubular frame was adequately tough and there was potential for massive improvement.
The CB wasn't a light bike to hurtle around and its overwhelming impression was of being rather vague. I often found the bike wandering off line by a foot or two when hurtling through bends. Knocking off the throttle sent it off on an even wider line, leaving me with the choice of twitching the bars as a prelude to a radical change of direction, or leaning over further which more often than not scraped the stand’s prongs or footrests. After a while, I started going into corners slower but coming out faster.
I rode the bike in stock form for about 4500 miles. As I didn't fall off it couldn't have been that bad! The need to pass an MOT meant the sagging rear shocks had to go. The breaker came up with a set of Marzocchi shocks that were so stiff I thought they came off a tractor. They were totally mismatched to the soggy front forks. As the front calipers spent at least half their time seized and the front wheel and steering head bearings were pitted, when the breaker offered a front end off a 1993 CB750 that had been back-ended I did a trade-in with him. The forks went on with surprisingly little hassle.
The MOT was passed without any problems. The Honda felt racing taut with the new bits but it was a bit uncomfortable for long distance work, as my body was subjected to a continuous stream of minor road bumps through the suspension. Cornering was so improved, with a much more accurate feel, that I had to saw off the stands' prongs to avoid doing pirouettes on them. The secure feel was even more emphasized when I replaced the worn out Dunlops with a brand new set of Metzelers. I could hurl the bike right over on the edge of the tyres and at a 100mph the plot was remarkably secure.
Top speed with the taller gearing was only 125mph, but the improved feeling of security meant that I could now stay with my mates' bikes in most curves and the reasonable comfort, taut suspension apart, from the flat bars and rear-sets I'd fitted meant that on long tours I could do several hundred miles before any pain set in.
A hard ridden and woefully neglected CB650 won't last very long, my friends kept telling me, based as it is on CB500 components, but I was doing a full service every 1000 miles and the taller gearing undoubtedly gave the engine a much easier life. In a year I did 20000 miles, which put 38 thou on the clock without any problems. By the time it had done 40000 miles, though, the camchain was rattling and there was some smoke on the overrun.
I had one of the first CB650s, a 1979 model with only one owner and 18000 miles. In many ways a dream buy as it had only cost £750 and was in very nice shape. With just 63 horses to overcome 450lbs the only problem was that the Honda was a bit lost amidst my friends who loved to wheelie and wheelspin themselves into oblivion. Acceleration could best be described as stately, even intense use of the throttle failed to provide much of a kick in the pants, although the engine took on a harder edge once 6500 revs were up.
Various so-called friends who reckoned themselves ace tuners offered all kinds of solutions to the paucity of performance but I settled for a used Motad 4-1 and K&N filter. These fitted without any undue hassle and didn't need any carb changes except for a bit of twirling of the pilot jets. It was an ideal moment to balance the carbs so a mate with vacuum gauges was summoned. The valves were all in perfect adjustment, there were only eight of them to check and just a single camshaft. The engine design harks back to Honda's second four, the CB500/4, which shared much engineering with the original CB750. The biggest difference is the wet sump on the smaller fours, although all the bits on the 650 share more with being an uprated 500 than a downgraded 750.
I immediately fell in love with the exhaust note, a muted throb below 7000 revs, thereafter a harsh wail. People sing the praises of twins and triples but I think the sound that a four makes on cam is the business. The motor was freer flowing, happier both to plod along at low revs and snarl all the way past ten grand. It still didn't have a hope against the other bikes but I was enjoying myself playing tunes on the engine, and that's what counts, ain't it?
The gearbox could've been better, though, there was a tendency to shoot straight past the gear required into a false neutral. By the time I'd located a working gear it was usually one or two ratios taller than I expected. A lot of the time I preferred to leave it in fourth, which would go down to 20mph and up to 90mph, a brilliantly usable range of power.
Top speed was 120mph, but it was accompanied by such secondary vibes that I was dissuaded from holding it for too long. Anything up to the ton, though, was permissible. However, the engine always had a revvy feel, even when cruising in top I was looking for another gear or two. When, after 4000 miles, the chain and sprockets were due for replacement, the chain needing 150 mile adjustments, I decided it was a good time to change the final drive ratios.
A gearbox sprocket one tooth bigger and a rear wheel sprocket four teeth smaller would give 15% taller gearing. I checked this out by taking off in second and third with the old gearing, encountering no problems. It's pretty pathetic really, that most modern bikes are geared to produce startling quarter mile times rather than for the benefit of the rider.
The whole feel of the Honda was changed radically. A deeper exhaust note and much more relaxed feel did not mean slower acceleration as it would take off in first and hit 50mph before needing to change up. The new chain had also smoothed out some of the nastiness of the gearbox, which was much less needed in town, rarely getting out of second.
100mph cruising was wonderfully relaxed, although top gear wasn't much use below 50mph. Obviously, the lower revving engine meant less wear and reduced levels of secondary vibration. Also, fuel went from a terrible 35 to 40mpg to over 50mpg. Out of interest, I cruised the bike for a couple of hours at 70 to 75mph, which was just tolerable in the slow lane, getting 62mpg for my pains. By no means exceptional, but tolerable for long distance cruising.
A lot has been written about how seventies muscle bikes handled, or rather how they don't. The CB650 was somewhere between the extreme of early seventies stuff and the implacable stability of later eighties bikes. Honda had gained sufficient knowledge of steering geometry and weight distribution not to produce a complete turkey. By the time the CB came into my hands, the suspension was worn out and some of the bearings were on the way out. The result was some quite large weaves but no nasty wobbles, which suggested the tubular frame was adequately tough and there was potential for massive improvement.
The CB wasn't a light bike to hurtle around and its overwhelming impression was of being rather vague. I often found the bike wandering off line by a foot or two when hurtling through bends. Knocking off the throttle sent it off on an even wider line, leaving me with the choice of twitching the bars as a prelude to a radical change of direction, or leaning over further which more often than not scraped the stand’s prongs or footrests. After a while, I started going into corners slower but coming out faster.
I rode the bike in stock form for about 4500 miles. As I didn't fall off it couldn't have been that bad! The need to pass an MOT meant the sagging rear shocks had to go. The breaker came up with a set of Marzocchi shocks that were so stiff I thought they came off a tractor. They were totally mismatched to the soggy front forks. As the front calipers spent at least half their time seized and the front wheel and steering head bearings were pitted, when the breaker offered a front end off a 1993 CB750 that had been back-ended I did a trade-in with him. The forks went on with surprisingly little hassle.
The MOT was passed without any problems. The Honda felt racing taut with the new bits but it was a bit uncomfortable for long distance work, as my body was subjected to a continuous stream of minor road bumps through the suspension. Cornering was so improved, with a much more accurate feel, that I had to saw off the stands' prongs to avoid doing pirouettes on them. The secure feel was even more emphasized when I replaced the worn out Dunlops with a brand new set of Metzelers. I could hurl the bike right over on the edge of the tyres and at a 100mph the plot was remarkably secure.
Top speed with the taller gearing was only 125mph, but the improved feeling of security meant that I could now stay with my mates' bikes in most curves and the reasonable comfort, taut suspension apart, from the flat bars and rear-sets I'd fitted meant that on long tours I could do several hundred miles before any pain set in.
A hard ridden and woefully neglected CB650 won't last very long, my friends kept telling me, based as it is on CB500 components, but I was doing a full service every 1000 miles and the taller gearing undoubtedly gave the engine a much easier life. In a year I did 20000 miles, which put 38 thou on the clock without any problems. By the time it had done 40000 miles, though, the camchain was rattling and there was some smoke on the overrun.
It was an engine out job, which required some strong muscles and a lot of fiddling with wires, carbs and cycle parts. Taking off the head I held my breath but could find nothing really wrong. Closer examination revealed that the exhaust valves needed a regrind, which didn't cost anything more than an afternoon's work, whilst over a hundred quid went west on a new camchain, tensioner and top end gaskets. It seemed like a good moment to stop the mild oil leak out of the head gasket. They are straightforward engines to work on but rather fiddly to reassemble.
The engine started up after about five minutes on the starter. It was lovely and quiet, rustling away like a new machine. Since then I've done another 14000 miles with no engine problems. The chassis wasn't so robust, with new swinging arm and rear wheel bearings as well as a lot of rust on the frame and cycle parts that was tedious to clean up as it kept coming back. Hard work rather than great expense sorted it.
There aren't too many CB650s on offer on the used market as they were never the most popular four. The best one I've seen was an 1984 job with only 5000 miles on the clock, but at £1500 it was too much for me. There are a few around at the £500 mark but judging by the engine rattles they need urgent attention. I've just bought a real rat for £200, but then it had done 69000 miles in the hands of more than half a dozen owners - the chassis needs a complete strip down and the engine smokes so heavily that it must need a head job and rebore. I haven't decided if I'm going to restore it or just use it for spares. By the way, both CB500 and 550 engines can be fitted in the frame if the 650 isn't available.
The CB650 isn't the toughest or fastest four in its category but they are relatively cheap and straightforward enough to upgrade to something more useful than Honda had in mind when they made the old beast.
Larry Riley
Larry Riley