b40 ss90

[beezabob]

Hi, just joined up having purchased a B40 ss90 to occupy me in my retirement. My question is the usual regarding frame numbers.
It is actually registered with the casting number in the logbook. However on inspection I have discovered a frame number on the frame under the tank. The prefix is slightly odd but the number matches '62.
It is      B4    41-4050
The engine number is
B    SS135    HC
which i understand makes it an early (35th built ?) ss90
Any info on whether that frame number is original would be appreciated.
pictures attached.
Regards  Bob

[JulianS]

That looks like a part number, it is not a frame number. many B40 parts start 41.

Your frame number would start B40 followed by 3 or 4 digit number.

Suggest check rest of frame for the number.

[DaveH]

Hi. The frame number should be on the opposite side of the swan neck where it connects to the down tube.

Regards,  Dave.

[beezabob]

Thanks for the quick response guys. Your pointer to where the number should be Dave reveals a number covered with  paint.. someone being naughty in the past. The bike was registered in 1984 so was probably then, I will check out the frame number later. Given that it has a drilled sump plug braced onto the sump cover I imagine it has had a hard life at some point. So I am guessing it is a ss90 engine been put into a b40 frame though it has been "replicated" nicely if the cycle parts are not original, Thought the odometer reading of 51800 was  too good to be true for an ss90.
Thanks for your help and I will update when I find out. Regards Bob

[JulianS]

B40 and SS90 frames were the same.

[beezabob]

So cleaned off the paint that was on the other side of swan neck..still no number. I guess the paint was just where someone else had done the same thing. Have looked carefully for other numbers and the only thing I could find was a part number at t the rear of the frame  this time  41-4020 . Different than the other. hmm.. jury is out .Anyway . Nice bike and after 56 years am happy to accept it as it is. And as an aside no doubt some noticed the concentric carb on it. The monobloc did come with it so something to sort out at a later date. Regards

[JulianS]

I would think that sometime in its life it has been fitted with a factory replacement frame, due to damage caused by a crash. The dealer was supposed to stamp the original number on the replacement frame, but they did not always do it.

The numbers you are seeing are part numbers for the frame forgings which together with the tubes make the whole frame.

You wont be the only owner in this position but if its got a V5C then enjoy the bike and dont worry about it.

[beezabob]

Thankyou for that info Julian , very helpful. And yes I will enjoy  the bike as intended. Just fiddling with it is taking me back to a misspent youth on bsa singles    Regards Bob

[AdrianS]

With regard to the concentric carb, if the bike runs well with that, then leave it on! I bought a B40 that had a concentric fitted but picked up a second hand monobloc. Had nothing but trouble with it - mainly from leaks at the base and the side cover. New monoblocs are quite expensive.

[Bsawill]

Hi just reading your old topic The frame number should read B40 plus frame number of our digits
The engine number is correct as b40 BSS and number for the ss90 models
Frame number never match engine number
Hope you still have the bike
My model is also a 1962 model ss90 and I am the only owner purchased from new
CheersBill

[scifi]

When you say plug braced, I suppose you meant Brazed on.  It's a neat idea to drain any wet sumping...  Wish I had that on my C11...