BSA B25 Starfire

Our roadtest on a BSA 250 unit single prompted Nigel Orchard to share his Starfire experiences, and he pulls few punches about the reality of riding an old bike on modern roads. Darrell Parsons and Bill Nelson chip in with some more hands-on expert advice about these characterful lightweights…

I enjoyed the article on the BSA Starfire in RealClassic magazine #137 as I have owned one for nearly six years. I bought it to be my local hack. It was advertised as: ‘restored 2003 including professional engine rebuild’ and sold to me in late 2009 with only 650 miles on the clock. I wondered at the low post restoration mileage. Could it have hidden problems? Its spec suited my needs and I liked the look of it.

Wary about the high compression ratio of the Starfire, I had gone after a Fleetstar that was advertised by a commercial vendor, but they decided they would get more by breaking it for parts and I did not find any others advertised.

Here’s one you can buy: a recent repatriation from the USA, listed on eBay for £2995 in June 2020. 

I’ve added another 2200 miles to the Starfire’s total since buying it. Rowena’s roadtest was right on the mark about ‘roadtesters must have benefitted from rubber mounted eyeballs… vibration is another bugbear… major angst… rattles and fractures…’ In my short mileage I have experienced: loss of petrol tank retaining nut and bolt, broken horn bracket, broken battery connection, broken rear chainguard bracket, fractured rear numberplate, loss of battery cover and tank badge (both fell off on one ride never to be found again).

The most productive ride of all was of 40 miles one evening. I began to recognise that it was not a good idea to drop the revs down to near-idle as the journey progressed but it was going well otherwise and I pressed on to my destination. On arrival, I found one retaining screw missing from the float chamber and the other half undone so there was a good gap between it and the rest of the carburettor. The charging circuit had failed and the rear light bulb had broken. With a replacement bulb and a borrowed screw for the float chamber, I made the 40 miles back in the dark without flattening the battery.

The article recommends regular maintenance to combat these and worse problems, but how much maintenance should one have to do, would one want to have to do in 2200 miles apart from checks on fluid levels? When we go out together my wife follows me on her 600cc Yamaha and kids me she does it to pick up the BSA pieces. Actually it was useful that she noticed where my numberplate fell off so we could go back and retrieve it.

Another problem I have is that despite new clutch plates and springs (hard screwed down), the clutch often slips and the kickstart does not turn the engine against the 10:1 compression, so I assume my bike is unusual. The clutch never slips when riding. Sometimes, continued kicks with the clutch slipping gets to a point where it is past TDC and does turn over. Sometimes I need to put it in gear and wind the engine back from compression by turning the rear wheel back (tiresome, dirty and undignified when you have an audience). Once you do turn the engine over it tends to start readily.

There are many positive aspects about the BSA 250 and these for me make riding the bike a real pleasure: good roadholding, a pleasure cogging up and down and finding neutral, light (non-dragging) clutch, good brakes, lively performance (though I try not to keep it at 70 for long periods and I do not push it above that), very manoeuvrable and that lovely ‘fruity tune coming from the…exhaust’. My wife says that dogs, horses and cows react as I pass.

I am prejudiced in favour of old British bikes but can see some good reasons why our industry failed and, at 68, I am increasingly jealous of the electric boot on my wife’s Yamaha.

What a pleasant surprise it was to read Nigel Orchard’s experiences explaining the foibles of his B25 Starfire. Rarely do I see any missives about B25 ownership, let alone actually see one on the road. Reading about problems and faults faced by other owners can be very rewarding and enjoyable. I have owned my Starfire for over 25 years, and with intermittent use over 25,000 miles have been covered.

When I bought the rolling chassis and later sourced an engine, I knew diddly-squat about motorbikes. It seemed a good idea at the time to have something old and British to use occasionally, something I could mollycoddle and cherish. Since then my ownership has been one long, sometimes enjoyable shake-down period where gradually I have sorted things and improved them where I could. I have learned a thing or two along the way and can draw parallels with the problems Nigel mentioned.

Vibration can be a problem but I alleviated much of that by default in that I had to take my crankshaft to Bassett Down Balancing after an inglorious incident during that initial refurbishment (told you I knew diddly squat). Having said that, I do get vibration, but not on the scale that Nigel is experiencing. The only items that have suffered are a small rear mudguard bracket and two short cracks low down on the rear mudguard. I have lost the occasional nut (who hasn’t?), and after a 240 mile ride I noticed that one of the tappet covers had gone AWoL. So my advice would be to have the crankshaft re-balanced, but be sure the correct ‘balance factor’ is applied.

Even so, my B25 does need a lot of maintenance. I used to joke that for every hour I ride it, I spend two hours maintaining it. Upon reflection, this might be true! After a satisfying ride there is nothing better than to park it in the garage and walk away, knowing it is there, ready to be used again without anything needing to be done.

I too had clutch problems but now happily that is a thing of the past. Clutch slip during starting is frustrating in the extreme. I even went to the trouble of buying a NOS clutch which was great – for a while and then it started happening again. All togged up, excited and ready to go and the bloody piston can’t get over top-dead. I even tried B50 clutch springs but with no lasting cure. No matter how well your B25 clutch is set up, it will be subject to slip due to that 10:1 compression. Rupert Ratio sums it up admirably in his book by saying that the clutch is a very good one but it is too small.

So there’s good and bad news: NEB make brand new, 16-plate (yes, 16!) clutches for the Starfire. Now the bad news: they cost a lot of money. However, it’s worth it because the time you spend in the garage on maintenance is massively reduced: once fitted, forget it and forget clutch slip. Another couple of tips. Change your oil every 1000 miles, that’s primary chaincase, gearbox and engine oil. Fit electronic ignition.

Regarding the on-going discussion about small capacity machines being suitable for older riders. Moving large capacity motorcycles around is dangerous for me and the bikes. Although I have lusted for a big twin all of my life, I have missed the boat. I am not too old, just too weak now. My bikes are all small capacity, Bantam D14/4, B25 Starfire and Honda CB72. The only downside is that it costs as much money to do up a small bike as it does a larger one, yet the value of the small bikes will always be substantially lower than for high capacity machines.

My B25T has the same clutch slip problem. I bought it as a rebuilt non-running project. Apart from the auto-advance actually being an auto retard unit, fixed by substituting a Boyer, the engine was harder to kick over than any Goldie I’ve ever been near, as a decent kick just made the clutch slip.

It does seem to have an unbelievably high compression ratio. Unfortunately, the mechanic who built it passed away just before I set about readying it for the road. No notes or photos of any use were supplied to the previous owner. When I got it started, it ran as rough as a badger’s rough thing and would have been unrideable on the road. I decided to sort the clutch first, with generous advice from Rupert Ratio in person and via his invaluable first unit singles book.

The first fix was a bit obvious, pattern cheesy springs had been fitted, readily identifiable seeing as they were wound the wrong way. Then I got hold of a NOS five-plate set from the later clutch and made the basic mods detailed in the book. I still need to machine the back of the basket and fit a thrust bearing to help the clutch to sit true-ish, reducing the normal wobbly basket syndrome. That done, I will then be able to machine or shim the front sprocket to keep the primary chain in line.

A common cure for excessive compression ratio on these engines (rather than fretting about mixes of piston and models) is to fit a plate betwixt crankcase and barrel.

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Words: Nigel Orchard, Darrell Parsons and Bill Nelson
Photos: Rowena Hoseason / RC RChive

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Want to know more? You’ll find the full-length roadtest we mention about a BSA Starfire in RC137: available mail-order or as a digital download.

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This article originally appeared on the earlier RealClassic website, several years ago. It’s been extended and updated with new images to suit the current incarnation of RealClassic online…