The Aquisition; my BSA B25 Starfire Project

Well dear reader, herewith the journal of my struggles to get this B25 back on the road. I have learned a lot in the process and this (as all my blogs) is simply the tale of my experience. I'm not a trained mechanic so I'm finding my own way generally assisted by various manuals, parts books and owners' forums. This blog is a simple way for me to record how I did whatever I did, the experience I had and what I have learned from it. Its written in a how-to  style but I don't necessarily recommend any of these approaches. However if I were to do the job again- its pretty much true that I would do it as described in these pages so if you do want to learn from my experience read each post through to the end rather than trying to follow it step by step- in some cases I discovered  later that perhaps I hadn't done things in the best order after all!  The usual disclaimers apply- I am not responsible for any loss, damage or injury resulting from anyone attempting to follow my steps and if you want professional advice then please ask a professional. Having said that if anyone has any comments or observations to add to these posts then please feel free to leave a comment- after all, its a learning process for all of us!


This bike was advertised as a starfire and I bought it as such. At that time I hadn't heard of a Fleetstar, but when I looked closely I found several features that weren't right for a Starfire.
My aquisition... and problems! Here are some pictures of the bike when I got it home.  The obvious concerns (which I had already noted) were that the side panels and oil tank were not GRP and not of the scalloped design. The fuel tank appears to be a Triumph item (although a nice one with a top rack) and the chain guard looks non-standard. The horn didn't work and although the bike started it revved uncontrollably suggesting there is a carb or throttle sticking problem.

Horn doesn't work, oil tank is metal and has no "eyes" for mounting a GRP cover.

Engine No. B25B means 1968. I don't know what the suffix "FS" means

Oil tank is metal and lacks some of the sculpting on Starfires. Fuel tank is a metal Triumph replacement, nice to see a tank rack though! Seat cover is torn.

Rear sprocket seems huge. Tool cover here is metal not GRP and although it has the triangular shape, its not sculpted as are the GRP covers. Note chainguard is chromed and I don't think the originals were, so I suspect this is a later replacement. Footrest rubber is split and needs replacing.

Full width front hub on 68 bikes- predates conical twin leading shoe versions.

if this is a tickler then its jammed! Carb appears to have no 928/300 so its a series 900 with a throat diameter of 28mm.

This rear sprocket looks awfully large and a bit "Trialsy" to me. Also the chain guard looks custom

928/300?

Instrument and switch on nacelle- is this the correct equipment?

Rear light is right

Odometer- 12591 at time of purchase.

Light to left is I think ign not oil pressure

ammeter and switch layout. Lights did work ... but not the horn so is it a dud or just a bad connection? In fact it was the latter and was sorted fairly simply.

Hard to read frame no... why is it ground? Appears to be B25B5627FS and thus matches the engine number.

The frame issue remains problematic. The metal covers and oil tank are typical of a 1970 bike, yet the Frame and engine number are both 1968. This could mean that they have been retrofitted and this would imply that the toolbox cover fits into the same fastenings via the oddie studs whether it be a metal or GRP panel. The '68 style oil tank has mounting lugs for its GRP cover but these are missing in my case, so I would need to change the oil tank as well  if I wanted to reinstate the GRP cover... although its quite possible that the cover would fit tightly enough over the tank itself.

Update:

Having consulted the members club it seems that the final FS in my engine number specifies a Fleetstar version. All the data I can find states that the engine number  B25B... is reserved for 1968 Starfires (where ... indicates the actual machine number). For a Fleetstar, the engine number should begin  B25FS ....  not B25B.... FS . Maybe the system was more flexible than the listings say? I also discovered that later (69/70) frames are distinguished by having two tubular lugs on the headstock (for use in fixing fairings) and only a single attachment stud (for the brake torque arm) on the drive-side swinging arm- earlier models have an upper stud for attachment of the chainguard. My bike fits both of these criteria and is therefore pre 69 and  I can discount the possibility of an incorrect frame number.

Further, the metal toolbox cover was always specified for the Fleetstar and I have seen a photograph of one other '68 Fleetstar  which also has the metal oil tank. Its possible therefore that the Fleetstars always had these items as standard, possibly because of better durability, and its the Fleetstar spec that gradually replaced the Starfire spec for privately-sold bikes. Fleetstars also had metal tanks- again because of the better durability of such an item and also the easy mounting for police radiosets into the rack mounting screws on the tank top. This raises the possibility that even my fuel tank might be original!  

Further update, appx 449 fleetstars were made by BSA and surprisingly and against the usual assumption, only around half (250) were police bikes. These were painted white, had single seats and a chronometric speedo, more accurate for police work. The remainder were painted black, had dual seats and were fitted with a Smiths magnetic speedo. They were sold to gvt depts mainly water boards, and a few were sold to private individuals. To make these more tempting I think it likely that they could have been fitted with the Starfire chrome mudguards although I cant find any evidence for this and the original supplier is long out of business; chrome guards would also have been a fashionable later modification. On this basis mine is probably one of the privately sold bikes which are the rarest type. Although there are no records of its history apart from the fact that it was included among a batch of police bikes despatched in July 68 to Blacknell motors of Nottingham, the multiple features do at least support one another and suggest that this was originally a privately sold Fleetstar.. or possibly a gvt bike.

I am still trying to track down the significance (if any) of the B25B engine number designation. The BSAOC have said that this simply meant an early bike, although the B25FS system is also listed as in use in 68 before September so maybe that came in just a few months later in the year. My bike has a 150 psi compression, and given atmospheric pressure is 14psi, thats a lot closer to 10:1 than 8:1 as used in the Fleetstar. However low compression pistons aren't available in oversize, so Fleetstars are likely to gain a C15 piston (and increased compression ratio) when rebored and this may well have happened to mine. I will see if I acquired the original piston with the stuff that came with the bike as if this is std it should pin down whether it was originally a hc motor.

Note from later- this bike has a high compression piston and has been rebored to +40.