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Bike Profile - Posted 18th May 2009

Yamaha XS650 vs BSA A50
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Karl Bentley has an owner's in-depth experience of living with a pair of classic middleweight twins from the 1960s and 70s. One was built in Britain, the other hails from Japan. Each has its merits, as he explains...

I must confess I like motorcycles, all motorcycles, and both of these machines are fine motorcycles for what they are. That's the rub isn't it? How many folk buy a bike and then moan because it doesn't do what it can't?

The BSA is the black one, while the Yamaha is the one in black. 1968 BSA A50 Royal Star and 1975 Yamaha XS650C

The 1968 BSA A50 Royal Star can't do 100mph. Well it could, just about give or take a few mphs, but not for very long I expect and not without needing a rebuild soon after. The 1975 Yamaha XS650C probably could do it with a lot more ease but you'd need to save up a lot to have all those fillings replaced afterwards, as the vibration would be rather intense. And the XS does have a 30% capacity advantage over the British twin, so a direct performance comparison between the two is hardly sporting. But that doesn't usually stop us, so…

The A50 engine is basically the same as the A65 apart from the cylinders and top end. In its Royal Star form it's a sedate A- and B-road tourer and there is no shame in that, especially on today's busy roads. Compared to the BSA the XS650 is a much more boisterous A-road machine which can take on motorway blasts, but it's a machine that can do sedate bimbling if you want it to. With more people finding pleasure in pottering around the lanes, I rather suspect these lowly tuned twins could find a place in more and more folks' sheds.

Actually very different. Engines: 1968 BSA A50 Royal Star (left) and 1975 Yamaha XS650C

The A50 with its 9:1 compression ratio and mere 32bhp can plod along happily at 65 all day, with the vibes just starting to make themselves felt. The XS650 with a compression of 8.4:1, 50bhp and 153 more ccs can add another 5mph to that before the vibes start to say 'no more' unless you want that tingling finger feeling after getting off the bike. That's not to say that both bikes won't go faster, but why would you want to? Indeed both the A50 and the XS650 can be tuned to go much faster but that's for racing and beyond my ramblings here.

Once you've got the bikes going then you'll need to stop, eventually, and here the BSA does have an advantage. That front brake on the A50 is one of the best drum brakes available on Brit bikes, without spending vast amounts of money that is. It's progressive, as in it slows you down more the more you pull on the lever, and in normal use fade free. In fact it is much, much better than the standard twin disc set up on the Yamaha. It shouldn't be, but Yamaha got the master cylinder to brake piston ratio all wrong, which means you have to really squeeze that lever for it to work. If you can squeeze it hard enough then it does work but there is no feel to the whole system -- hence the term 'wooden'.

BSA brake works Brakes: 1968 BSA A50 Royal Star

If you add a bit of rain to the equation then the stainless discs make for even more heart stopping moments, though new pad materials have reduced that 'oh my God, I'm going to die!' effect. Some owners even have their discs drilled in an attempt to alleviate the problem.

Yamaha mudguard fits. Brakes: 1975 Yamaha XS650C
XS Yamahas on eBay.co.uk

The rear brakes of both bikes work well though the A50 seems to require a lot of movement in that long brake lever before anything happens.

Now we've dealt with going and stopping I suppose a mention about bends would be in order. Everyone knows that the XS650 has never had a good reputation for altering direction, indeed much money was thrown at Percy Tait to make it better and the resulting bracing dotted around the Yamaha's frame is evidence of that. I found the main problem with the XS650 roadsters was that feeling of being perched on top of the bike rather than sitting on it. This is all to do with the relative positioning of your hands, feet and backside and on my bike it felt all wrong. So I sliced an inch or so off the seat foam and for me this transformed the bike's ergonomics. Now I feel much more part of the bike as I have always done riding the A50. This hasn't made the Yamaha handle any better, but it has made me feel a lot happier piloting it.

In a straight line both bikes are perfect, the Yamaha having a more responsive front fork action to larger bumps, which might be down to the fact that I need to replace the BSA's lower stanchions, as they are fairly worn; a problem on these BSAs, as the lower stanchions were fairly lightweight to start with. Having said that, I have ridden other A65s with the same Triumph-style poppet innards and they have been amongst the best Brit bike forks I've experienced. Overall the BSA has the best handling: rolling into corners with little rider input and picking up again easily, unlike the XS650 which needs a lot more effort from the rider. But I have to own up to running the XS on older Speedmaster tyres that probably don't do a lot for its handling and the BSA on more modern Road Runners, which do.

Black, The one true colour. Engines: 1968 BSA A50 Royal Star (left) and 1975 Yamaha XS650C

Both these bikes came with 12-Volt systems and points and coil ignition. A previous owner installed a Newtronics setup on the XS650 which replaces the points but keeps the mechanical advance mechanism. Something you need to keep an eye on, as the small springs wear out and can give erratic running problems. The original Yamaha mechanical voltage regulator developed a mind of its own shortly after I acquired the bike, but a forty quid reg/rec from Excel spares was a straight plug-in replacement for it and the original rectifier pack. This by the way I found in a stupid position under the battery holder where it could rot away quietly. The BSA had its old crumbling Lucas alternator replaced with a modern copy and a solid state reg/reg unit. I upgraded the ignition with a Pazon Surefire system, which I have been very impressed with.

The Yamaha came with a very sickly electric foot, which I lopped off and threw into a box. One of the problems was that the battery size available couldn't cope with the electric foot for more than one or two attempts. With the recent advent of more powerful gel batteries, I am tempted to reinstall it and see how it goes. Both bikes start easily on the kickstart. The XS needs choke when cold and will fire up after a couple of kicks. The A50 needs a good tickling, till petrol emerges in fact, then it too will fire up, usually on the second swing. The choke doesn't seem to have much impact on the BSA.

Narrow. Nice. Head On: 1968 BSA A50 Royal Star (left) and 1975 Yamaha XS650C

Gearboxes are fine on both bikes, the Yamaha needs its clutch set up just right or you'll find neutral hard to acquire at a stop, otherwise the old practice of snicking it into neutral as you roll to a stop is recommended. The BSA box is a tad clunkier on down changes than the Yamaha. I added an SRM pressure plate and needle roller conversion to help things along. Both clutches, though not light, are easy enough to get along with.

Both bikes approach lubrication in different ways. The Yamaha has a wet sump so carries its oil down low and filters it through a fine metal gauze filter in the sump and another smaller metal gauze filter on the side by the oil pump. The BSA carries its oil in a tank under the seat and relies on more frequent oil changes and a much simpler system of crank-based sludge trap and settling out in the main oil tank and sump. In order that I could use modern detergent oils, I fitted one of Paul Goff's (www.norbsa02.freeuk.com/goffyoil.htm) spin-off filters to my A50. I also added a sump plate with a magnetic plug to make oil changes easier.

Finding spares for both bikes is easy, the BSA probably being the best supported, though recently a German based XS parts dealer (www.xs650shop.de) has come on to the market to replace the sad loss of Tony Hall of Halco, who was the main Brit XS parts dealer. I've also discovered that most Yamaha XS650 came with a 17 tooth gearbox sprocket. Changing to an 18 tooth one drops the revs at 65-70 making the bike much less vibey and more motorway friendly and hardly changes the acceleration off the line.

Like Ant and Dec, they're always on the same side of the screen. 1968 BSA A50 Royal Star (left), 1975 Yamaha XS650C (right), KarlB (centre)

I've found a place for both of these bikes in my garage. I'm glad I don't have to choose between them because I couldn't. But if I had to, well, I suppose it would be the BSA, only because it takes me to more Brit bike events. Ideally, I'd love to put the XS motor into the BSA frame just as a few other folk have done. I wonder if they'd let me have a go?

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More info:

  • Classic Japanese Club: www.vjmc.com
  • BSA Owners Club: www.bsaownersclub.co.uk
  • Paul Goff oil filters: www.norbsa02.freeuk.com/goffyoil.htm
  • XS650 Shop: www.xs650shop.de


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