BSA B21 BUILD............................................
A couple of trial runs reveal just how much fine-tuning John Lay’s 1938 250 single still needs. This month he tries to find all four gears and a front brake; fettles the forks and fixes a fuel leak, then discovers the gears have gone AWoL again…
A couple of trial runs reveal just how much fine-tuning John Lay’s 1938 250 single still needs. This month he tries to find all four gears and a front brake; fettles the forks and fixes a fuel leak, then discovers the gears have gone AWoL again…
There are many situations which can be resolved during a rebuild when the machine is static, but some things don’t become apparent until it’s running. After last month’s trial run several of these became apparent, starting with… where’s all that oil coming from?
That’s the thing about clean, new oil – it’s not so easy to see. It mostly seemed to be coming from the oil return line where it joined its union. The line was crimped on the union but clearly not crimped hard enough: not too difficult to fix. Re-crimped and reconnected, the tank was re-filled and left overnight with a drip tray underneath. There was no oil in the tray on the following day. I know the old joke; ‘If a BSA doesn’t leak oil, there isn’t any in it’ but still I think the oil is better in the engine rather than on the floor.
Next: was the dynamo charging? No it wasn’t. It was unlikely to be the dynamo itself, which was a newly reconditioned unit. More likely the problem lay with a very secondhand regulator box. At this stage it’s not really a priority – the lights work from the battery and this problem wouldn’t stop the bike being used in the daytime.
Of more concern was the gearbox, which caused some problems in the early stages. It proved to be all but impossible to select gears when the bike was stationary, but gears could be changed when the box was spun over with the kickstarter. I have come across this before with BSA boxes, they are of the constant-mesh style with the gears being selected by sliding dogs. If these are not in the right position relative to each other then they simply won’t engage. But with the engine running and, therefore the box rotating, maybe they would play ball. The bike was lifted onto its rear stand to get the rear wheel clear of the ground, and the engine started. Happily, yes; all four gears were to be found.
The next challenge for the gearbox would be an actual road test with the cogs under load – who knows what more problems that might reveal?
Even before that stage, just pushing the bike up and down the garden path showed the front brake to be more or less useless. The brake was offering useful suggestions rather than practical help. I’d used a Bantam wheel for want of the proper one to move (literally) the project along. Bantam brakes are not that good even in a Bantam, but I thought they should at least do something. My two wheels came complete with brake shoes so I just used the set that seemed in the best condition. Even so there was a lot of ‘lost’ movement, so much in fact that the brake lever came all the way back to the handlebar.
I acquired a new set of shoes, and comparing the new with the old showed that the new ones had quite a lot more meat on them, so much in fact that they needed a little bit of fettling to make them fit the drum. With the shoes fitted and the wheel back between the forks, all of the lost movement was gone and it was now possible to apply a decent amount of pressure to the brake lever. I still didn’t know how good it would be on the road – but it couldn’t possibly have been any worse…
The engine test run revealed another fault; a blow in the exhaust pipe. Welding it up proved to be a bit of a game and I ended up chasing the hole round the pipe with the torch, but we got there in the end. Once the weld was dressed off it didn’t look too
bad, but it was a bit like a patchwork quilt. I thought some high temperature paint might do the trick to improve the look of things. My local motor accessory shop had a selection and needless to say I chose the wrong one! I came home with silver which, although it gave a nice finish, looked awful, completely out of character with the rest of the bike.
So the following day I took it all off. This type of paint cures by heat but as I had not run the bike it came off easily enough using a rag soaked in thinners. I improved my local motor shop’s profit margins with another can, this time aluminium. I started again, with better results this time.
The next problem – the rear stand had bent. This was a home-made affair and the bits of push bike chainstays were not up the task. They had been strong enough to support the bike the whole time it was being worked on without any problems. So what was wrong now? Of course, I’d started it up for the first time with the bike on its stand. Bouncing up and down on the kickstarter with the bike on its stand is not a very good idea. Happily they straightened out again fairly easily.
Another ‘little job’ was to sort the primary chaincase. This had been fitted temporarily for the test run. As the clutch seemed to be behaving itself I could secure the case properly – but there was another missing bit to find or fabricate. BSA pressed cases are not the most oil-tight of affairs at the best of times, and having two large holes in them where the footrest mountings pass through doesn’t help. There is, or rather there should be, a flanged sleeve that slides over the footrest support with a pair of cork washers, one at each end, which seal against the inner case faces. This needed to be quite a chunky piece as the footrests are around 7⁄8” diameter. Fortunately there is enough room for it, so one was turned up from an odd piece of steel and a pair of cork washers cut from sheet.
Next – fit the outer case. There is a cork seal between the two halves and the whole thing is held together by 16 small, cheese-headed screws. These (supplied by Draganfly) were of course brand new, bright and shiny and looked quite out of place in a project of this nature. They stood out like the proverbial sore thumb. Heating the heads with a torch to bright red and then dipping them into old and dirty oil gave them a more appropriate matt black colour. Once the case was fitted a small quantity of oil was poured in; the right amount indicated by filling to the level plug near the bottom of the case.
Before venturing out onto the Queen’s Highway I felt an MoT might be a good idea. Bikes of this age are MoT exempt so I had already insured and taxed it, but having spent so long restoring and repairing a machine it’s possible to become too close to what you are doing. An extra, independent set of eyes was called for to provide assurance.
Did it pass? Yes it did, even that Bantam front brake made the grade. However in the process the nipple pulled off the end of the brake cable: better for that to happen at the MoT station rather than when some clown pulls out in front of you! There was also a bit of play in the rear wheel – they are cup and cone bearings so just need readjusting – and the front tyre, although legal, needed replacing. I planned to change the front wheel completely, which would be the right time for a new tyre.
The BSA’s MoT coincided with the date of the Great Dorset Steam Fair, so its first outing was to the fields of Tarrant Hinton – which showed up another couple of faults. Gear selection when pulling away was a bit problematic and, more seriously, the petrol tank leaked. It wasn’t leaking from the bottom as you might expect, but halfway up. Riding with a full tank over a field shook things up so that fuel ran down the outside of the tank from behind the offside knee pad. Not good!
The knee pads are held on by a pair of cheese-headed quarter-inch screws that fit into threaded sockets welded into the tank side, and one of these welds was leaking. Corrosion had set in around the weld area until it had become porous. Welding in a new socket or re-welding the original might seem the answer, but using a welding torch around fuel tank is NOT a good idea, Don’t try this at home, as they say.
I decided to use solder, which still involves heat but a great deal less of it. I was able to complete the job using nothing more than a hot air gun, normally used to remove paint. I thoroughly cleaned the area using solder paint from a motor factor; it’s used to prepare body panels prior to ‘leading’ up. When applied and heated, the solder paint changes colour to black and can be worked onto the steel using a wire brush or even steel wool. With the area thus ‘tinned’ then the ‘lead’ can be applied. This is solder, but not the sort you use for electrical connections, which is much too fluid when molten. The type used by plumbers to make ‘wiped’ joints has a plastic state over quite a temperature range so it can be spread on. It doesn’t look very pretty but as it’s behind the knee rubber no one’s going to see it anyway. More to the point: no naked flames were needed. A decent tank sealant may be worthwhile.
The fields of Dorset showed up other areas which needed adjustment; the front forks and the rear chain. New chains always seem to go slack shortly after fitting and this one was no different. Adjustment is quite simple on the B21 as the wheel spindle is fitted with a pair of snail cams that bear against pins fitted on the frame at the end of the chainstays. You simply slacken off the wheel nuts, apply a spanner to the square formed on the end of the wheel spindle and rotate in the required direction. This in turn rotates the cams and moves the wheel. Once done, do up the nuts and don’t forget that the rear brake will probably need to be adjusted as well.
With the front forks, the idea is that they should move up and down freely without any side play. Too tight and you could restrict or even prevent free movement. Too slack allows sideways movement which does not do the steering any good at all. Either can lead to premature wear, through excessive friction between the spindle housings and the links, or from sideways chatter.
Adjusting these girders is, in theory, simple enough. Slacken off the locknut, wind the spindle in using the hexagon at the opposite side, do up the locknut. In practice it takes a little more tweaking to get just right because doing up the locknut will almost certainly put the adjustment out a little. I found that doing up the spindle until it was just tight and then backing off by one flat of the hexagon, then doing up the locknut was very nearly correct. Compared to tele forks, girders demand more attention which they don’t always get. That’s probably why these were in such poor condition.
Next job was to adjust the steering head bearings: slacken off the pinch bolt ( just below the handlebar clamp), then un/tighten the large dome headed nut on the top. Don’t forget to do up the pinch bolt afterwards.
The nights were starting to draw in, so something needed to be done with the lights. They worked from the battery but weren’t getting any charge. I initially put it down to the secondhand regulator – swapping to another made no difference so I bought a new electronic one instead. This was mounted in the case of an old regulator and duly connected up. One problem. Still no charge!
Previously, I’d purchased a rubber shroud which fits over the connections on the end of the dynamo. When fitting this shroud I’d needed to disconnect the wires. Thinking about it… lightbulb moment! Had I got the wires F and D the right way round? I thought I’d played safe by putting markers on the ends and checking them with a meter but – just for the hell of it – I swapped them around. Yes, you guessed it, the bike started charging right away…
With these issue resolved I returned to the gear selection, which was almost impossible when stationary and a bit hit and miss when moving. Sitting astride the bike and rocking it backwards or forwards was enough to select a gear. Finding the gears when moving was clearly going to require a bit more thought. Foot-change gearboxes are, in the normal way of things, fitted with positive-stop arrangements. When you move the gear lever in the required direction to select a ratio, the lever then returns to its mid position. There’s no such arrangement on a hand-change box: the lever stays where you put it and unless it stays in the right place you don’t select the correct gear. The old story of having a box full of neutrals might well apply here. To help position the lever it operates in a zigzag gate fixed to the side of the fuel tank.
Where the zigzag slot changes direction at right angles, a shoulder is formed and this provides a ‘stop’ for the lever. But to be effective the gate, lever and gearbox must all be correctly positioned relative to each other, and to achieve this a couple of adjustments are provided. The gate fixings are slotted to allow a small amount of up and down movement, while the rod connecting the gearbox to the selection lever is adjustable for length. Two adjustments, twice the chance to get it wrong!
Both the hole in the end of the gear lever and the clevis pin in the rod were badly worn. This meant the lever had to be re-bushed and a new pin made – and that operation was required at the gearbox end as well. The wear in these two joints added up to a fair amount of lost movement at the outer end of the selector lever. It’s important to get right because the primary chain is adjusted by moving the gearbox backwards or forwards which also affects things.
Testing gear selection on the road was the next step. Although by no means finished (are projects of this nature ever really finished?) the B21 was street legal. I use a minor road which climbs a steep hill out into the countryside, where it peters out into a dirt track. The steepness of the hill gives a good test of the bike’s performance… and if it conks out then I can just turn around and freewheel home.
On a dry, mild day the B21 performed rather well. It steered well with the front forks and sprung saddle soaking up the road bumps. The motor seemed quite lively, more so that my BSA C11G, which is probably more because the older bike weighs less rather than any extra horsepower. After a little bit of tweaking, I even found all four gears. I reached the top of the hill without having use bottom gear: it climbed up quite easily, but coming back down was something else! That Bantam front brake might have passed the MoT but it was certainly a bit on the feeble side. The new shoes were an improvement, but although they slowed the bike on the descent I don’t think there was any realistic hope of actually stopping. Time to find a permanent front wheel…