Friday, 3 April 2009

In case you haven't read my first post this is a page from a web site I built about 5 years ago, it gives some background to my TriBSA.

Welcome to my bitsa motorcycle page. 

This page is dedicated to motorcycle 'bitsas', that is motorcycles that are made up of bitsa this and bitsa that. If you prefer full restorations then this probably isn't the site for you. However if you cannot resist the urge to take perfectly good motorcycles and 'improve' them then you'll feel right at home here.

First some history

My interest in bitsa motorcycles began in 1984 when I was 17 and I desperately wanted a British bike (in contrast to most of my friends who either rode or aspired to big Kawasaki fours). Despite not having a full motorcycle licence I bought a 500cc TriBSA and attached a sidecar to allow me to ride the thing on L plates.The TriBSA consisted of BSA A10 rolling chassis mated to a T100 pre-unit engine and was styled to resemble a pre65 trials bike, a poor man's Metisse if you like. Naturally I 'improved' it by painting the tank matt black and adding a tombstone rear light.

The first time I took the outfit out I had a scarey moment, the classic swerve right when braking that many outfit pilots experience when learning the black art of sidecar handling. I nearly crashed into a wall and survived the incident with little more than a burn where the high level pipes (which I had, unconventially, mounted on the right to allow fitment of the sidecar) were pressed against my leg. I decided that I needed a few lessons. A friend assured me that he knew what he was doing and the following weekend we set off with me in the chair for my first lesson.

Within a quarter of a mile he failed to negotiate a left hand bend and put himself, me and the bike through a garden wall. I blame myself. I hadn't actually specified that I wanted lessons in not crashing and I assume that, unimpressed with my first effort, he thought I wanted to learn how to really crash an outfit.

I had quite a few adventures on the old TriBSA but found I spent more time fixing it than actually riding it. For this reason I never managed to pass my test and fell foul of the two years on one year off provisional licence laws. I eventually passed my test on a borrowed MZ and started to ride a selection of (now no doubt classic) Jap bikes. However I never got rid of the TriBSA.

Inspired by the images in the pages of Back Street Heroes magazine I decided to use the TriBSA a the basis for a chop, I stripped the engine and gearbox out of the frame, a friend welded on a home made hardtail rear and I started to throw money at my 'project'. However, my enthusiasm outstripped my finances (this was the late 80's and I was being crippled by a sky high mortgage) and the TriBSA slowly shifted into 'unfinished project' status.

In 1992 I was thrown a lifeline, I was offered voluntary redundancy the same month as I sold my house. This gave me enough cash to clear my debts and have some money left over. With no job but cash in the bank the TriBSA was no longer an unfinished project but work in progress. I enrolled in a mechanical engineering course at the local technical college and was allowed to use the workshop for anything I wanted. This proved invaluable for the manufacture of the inevitable brackets and spacers that need to be manufactured when building bitsas.

It wasn't long before the rolling chassis was nearly complete. At the back the hardtail held the original A10 rear hub laced to a wide 16 inch rim while at the front a pair of alloy slab yokes held the forks from a SOHC 750 Honda. All that was required was the paint. A friend who I shared a garage with offered to do the job and a deal was struck. Then, disaster, when the frame was hung from the rafters it became evident that it wasn't straight. I still don't know if the frame was bent went I bought it, whether the abuse handed out to it when I had the sidecar on it (which included loading the chair with everyone's beer and a passenger on the way to the Kent Bike Show) or the home made hardtail was to blame but whatever the cause the frame was scrap.

I now had to make a decision, I was tempted to just forge ahead with the suspect frame but in the end decided that a new frame was the way to go. I thought about buying an off the shelf hardtail frame or even having a totally custom frame made up but in the end lack of funds dictated that the best route would be to buy another, secondhand A10 frame. This time around I decided that rather than a hardtail I would achieve the long 'n low chopper look with an overstock length swinging arm and a short pair of shock absorbers.

I had decided to install a larger engine than the original T100 engine (which would have required a complete refurbishment). Searching through auto-jumbles I bought a set of pre-unit crank cases and I proceeded to use these as the basis of a 750 pre-unit engine using components from over 30 years of Triumphs.

I eventually completed the project in 1995, jumped through the hoops to register it for the road and finally got to ride my dream bike. What a disappointment, I had built a monster. Long and low might look good in magazines and I'm sure that for some people it's the only way a motorcycle should be but I hated it. You see the problem is I like corners but the long and low look meant the ground clearance was appalling, it would grind out at the slightest provocation and on a number of occasions the solid footrests would hit the deck so bad that the rear tyre would break traction. To top it all the engine still needed development. I discovered the hard way that the timed breather arrangement requires a hollow inlet cam whereas the 750 inlet cam I installed was solid. I fitted an atmospheric breather to the timing chest but found that this allowed a lot of oil to escape the cases.

By this point I was engaged in post graduate study for my PhD and I didn't really have the time to work on the bike, especially as I now wanted to completely change the bike again to make it go round corners. I sold the knackered car I had been using as day to day transport borrowed some money and being rather disillusioned with my long and low British bitsa went to the opposite extreme and bought a completely original GSXR 750H. Very fast, never ground out while cornering, got me busted for speeding for the first time in ten years within two weeks and was stolen within three.

I bought an FJ1200 with the insurance money, a bike that has served me well for the last 5 years and one that has plenty of potential for modification (I have fitted a FZR Genesis wheel) but now I am in a steady job with a steady income and despite what past experience should have taught me I can't resist the temptation of throwing more money at my old TriBSA.


  1. Great story Chas. I am just at the beginning of my Tribsa story. I almost have a complete set of parts to build a pre unit t100 Tribsa (am I deluding myself?)and hope to start a dry build soon.I haven't got a clue what I'm doing but theb best way to learn is to make mistakes.
    Keep blogging and we could possibly meet in about ten years when I have completed my Tribsa!
    Regards Chris C

    1. i was interested to see your article, i have had a tribsa scrambler for over 40 years, in various forms and states of repair,i notice the front fork change, im trying to fit cerianis to mine - has anyone got any suggestions re the headstock bearings and set up? any help would be appreciated,
      cheers all.

    2. Re fork change, I used taper roller bearings from SRM (AIUI they're a modified off the shelf item) so I had the yoke stem made to fit the bearings but it's usually pretty easy to either make a new stem or make some spacers.