Buyers' Guides

Friday, 29 June 2018

BSA B25


I should have just left it there to drown in its own filthy oil pool if I'd thought rationally about it, but as is often the case I set my heart on it before I'd even seen it. Reading the usual five minute road test in one of the classic rags had left me convinced that a BSA 250 B25 was a true sports thoroughbred capable of an easy 80mph with heaps of low down grunt and built to last for ever by some of the finest craftsmen in the world.
 

What a mug. The old nail I was peering at was a complete wreck. Oil oozed from every joint and the paint was like a leper's stump with bits flaking off everywhere. For a tenner as a spares-or-repair it would've been expensive but for the £200 I handed over it was bloody fraudulent. Of course, it did come with a big box of useful spares like a broken drive chain, smashed cylinder head, ruined piston and about forty warped clutch plates.
 

Surprisingly, the engine did work - and it was MOTd. The ride home was full of thrills as the box of knackered alloy slid perilously from one side to the other occasionally smashing into my solar plexus as I grabbed a handful of the amazingly effective TLS front brake. The exhaust note was superb, especially when cracking the throttle open in third exiting a bend, so much better than my tired old Bantam. This was obviously a real classic to love and cherish.
 

What I'd actually bought was a bored and stroked version of Triumph’s 150cc Terrier, introduced in 1953. By 1970 the B25 pumped out about 20hp from its OHV 250cc engine at around 6000rpm. Not particularly impressive, these days, or for that matter back then when it was introduced in a rather pathetic attempt to beat off the Jap 250s. Of course, it was too little too late. Instead of designing a totally new machine the boffins at Small Heath simply tuned an existing design and hoped it would hold together.
 

The gearbox was basically the same as the 15hp C15 introduced way back in the fifties. A real recipe for disaster. The oil was held in the frame like a late Bonnie. Electrics were the typical dismal Lucas products but at least they were 12V rather than the appalling 6V rubbish found on most British lightweights. Top speed was reputed to be around the 85mph mark. My first doubts about the bike came when a couple of friends dropped by and collapsed, blubbering in hysterical laughter, when I told them of my new purchase. It was even worse when they saw it. Undaunted I cleaned up the oil leaks, serviced it and gave it a fresh coat of black paint. A vast improvement... well, for the first 10 miles before the oil leaks came back.

Out on the twisty back roads I loved it. The handle was precise in a way I'd never come across before on any of my Jap hacks or my flexing Bantam. Once on a line it stayed there no matter how bad the terrain, but, of course, any modern 250 hot-shot would make it look pretty damn silly under any conditions.

The brakes were really excellent and could handle twice the power but were really only necessary if something nasty should happen like a deaf and blind car driver pulling out suddenly. Under normal silly arse thrashing conditions you could rely on the engine braking in third to lose speed before chucking it into a series of bends, whacking open the throttle on the exit then snapping it shut quick again before banking her over for the next bend.
 

All good fun but not so smart in terms of tyre and chain life (5500 and 7000 miles respectively). On major roads it was a totally different kettle of fish. Up to 50mph the motor was very rough and snatchy, reluctant to pick up in top gear, which meant constant down changes to pick up speed in traffic. On a Jap bike this would be no problem but the crunchy, imprecise bastard of a gearbox made it a misery often resulting in a false neutral or terrible metallic grinding noises. Things smoothed out a bit between 55 and 60mph with a slight tingling vibration through the bars and footrests but nothing serious. 

Going beyond 60mph made things deteriorate rapidly. The vibes became intrusive and teeth rattling; by 70mph it was impossible to hold onto the bars, the vibes were so bad that it was agony. Motorways were out of the question but I thought that if I sorted out the lower end of the rev range Id have a nice little 60mph cruiser.
 

A new set of points and advance/retard mechanism made not the slightest bit of difference, nor did the very hopeful offering of a new spark plug. It was obviously a carb fault, so after sodding around with various jets, needles and slides all to no effect, I finally dug deep into the old wallet and shelled out a fortune for a new carb - predictably it made not one iota of difference. Riding around on a bike with a usable speed range of 50 to 60mph is a bloody misery. On certain boring stretches of road I frequently lost my patience, pushed up speed to around 70 with a total indifference to the destructive effects this might have.
 

After a couple of months of this the front peg stays had snapped, bulbs blew with monotonous regularity and various minor bits dropped off, like the front brake lever, rear lamp lens and pillion footrests. It looked a mess when I bought it but now it was a complete heap. I was scared of leaving it parked for long in case the refuse collectors took it away. I began using the old Bantam again. I was really pissed off and came to the conclusion that the engine must’ve been in need of a total rebuild.

The motor came apart easily enough with just the odd ruined thread. Inside the engine there was no real sign of wear but just to be safe I changed the rings and various bearings, which were commendably cheap. The gearbox was a bloody mess, most of the teeth were either worn away or snapped off. I couldn't afford a new set of  internals so I learnt about the art of autojumbling... the hard way.
 

Most vendors seem to lie like politicians and, of course, I ended up shelling out for a completely wrong set of gears. On other occasions | was forced to search through boxes of absolute rubbish, listening to some idiot telling me that the twisted lump of metal I was looking at was in fact a a TT racing cluster for a B25, but I was not going to be had again. Eventually, I got what I wanted and put the engine back together again. Feeling exceptionally keen I tidied up the chassis.

What a waste of time. The bike was just as bad as before. After the initial black mood had worn off I decided to run the thing in as carefully as possible. This wasn’t too bad as the gearchange seemed vastly improved. After about 300 miles the clutch stopped trying and 50 miles after replacing that the exhaust valve burnt out. I replaced both valves and guides; | was taking no chances. After 500 miles I figured it had to be run in so I started using the revs. It was still agony above 65mph but the smoother gearbox meant it could be hustled around town quite happily with a fair amount of fun; leaving Superdreams standing at the lights was my favourite little game.

Like a real moron I decided I had to see the fabled 85mph on the clock. It was a warm pleasant evening with the sun slowly sinking down and hardly a car to be seen. It seemed as though miles of sheer joy stretched out before me as I opened up the vibrating, wheezing old Beeza beyond 70mph. She pulled well up to 75 then began to suffer a little valve bounce. The vibes were unbelievable. I should have throttled down but instead just kept her wide open, mesmerized by the deep wailing growl from the baffleless silencer.

In a flash it was over. One very loud bang and the wheel momentarily locked and then freed. I looked down in total disbelief at the engine which was gushing out oil and shrouded in thick smoke. Closer investigation revealed that the con-rod had broken free and smashed its way out of the cases. What a mess, the whole engine was a write-off. I wanted to shoot myself for being such a bloody imbecile, the average gibbon would have realised a blow up was imminent.

It was back to the Bantam. The wretched B25 had cost me a fortune and lasted a miserable five months and 5500 miles. The trouble with running a Bantam is that every time you stop for fuel you get accosted by some wheezing old git who’s only interest in life is lying about the old Bantam he owned back in the fifties. But on one occasion, one announced he had an old B44 engine. I bought it for a fiver (yes, this happened some time ago) and wasn’t shocked to see gallons of oil pouring out of it when I fitted the engine and connected it up to the oil tank. All the seals had perished...
 

The B44 was a 441cc OHV single with a modest power output of around 30hp. The cranks and bearing are beefed up compared to the 250. On the road, it was a complete contrast to the smaller bike, as it was much smoother as smooth as a large single has a right to be. The engine pulled happily throughout the rev range and could manage a respectable 90mph although vibration did get a little harsh. I felt this was a bike to stay with so I spent a great deal of time and cash doing up the cycle parts. In the end it looked and went well.
 

The stable sure-footed handling perfectly matched the lazy engine when cruising at a sensible 75mph along a motorway with just enough vibration to let you know what the engine's doing although on really long runs I taped foam around the bar grips. On the other hand, it was delight to chuck through the curves, feeling light and nimble as you banked from left to right with just the silencer touching down as it neared the limit.

Coming home after a really long and pleasant run I began to notice a slight tendency for the rear wheel to slip. I pulled over and found oil everywhere - the oil feed pipe had broken but no engine damage. This is one of those bikes that can get to you. I kept it for a while and did around 16000 miles a year. Nothing fell off as I used Loctite and rubber mountings. As a day to day workhorse it let me down just once which for an old nail was pretty good going.
 

I eventually sold it in the search for more power and twin cylinders. On the whole, a very pleasant machine, but B25s should bear a government health warning.

Andy Everett