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Topics - Dabbist

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Singles / polished B40 crank cases
« on: 08 November, 2017, 14:34:39 »
Hi again chaps.
                      Being a bit strange, I've always been slightly niggled by the sight of rough cast crank cases sandwiched between bright shiny primary drive and timing side covers.
Can anybody out there think of a good reason not to polish them?
I presume the rough cast will cool slightly better than a polished surface, but I can't imagine that being a problem at all.
There's a fair amount of material to remove, but the theory applied to con rods etc is that the result is stronger, due to the absence of stress nodes, and that the raised bits do nothing for rigidity.
My guess is that the only logical objection left is that the castings may have imperfections below the surface, but that seems unlikely.
Of course there's always keeping them shiny to consider, but finishes like Zoop seem to work well in other places and it should actually be easier to clean than the rough surface, as there's no key for muck to stick to.

2
Singles / B40 with B25 Cam
« on: 31 October, 2017, 15:23:22 »
My understanding is that fitting a B25 cam to a B40 will (with the flat cam followers) give the same result as an SS90 cam, which is what I want to achieve.
According to RR and others the case will need machining to accommodate the cam followers and/or the greater base circle of the cam, I'm unclear on which or both.
Can anybody enlighten me on the nature of the machining?
Is this just a non-critical clearance problem that can be eased with a die grinder, or is it a precision job?
Also, the Otter site shows a custom bush for the camshaft. Is that a part which can be bought? I'm not sure my large and ancient lathe will be accurate enough to produce one :-[

3
Singles / B40 Piston
« on: 30 October, 2017, 19:31:44 »
Hi Chaps,
              Having got my engine apart (well, the top end do far) and done a bit of measuring, it's clearly time for a rebore. I intend to fit a high compression piston anyway, but I'm having a lot of difficulty finding one.
There seem to be quite a few places selling the JP ones, but I keep reading horror stories about poor machining and frequent seizing.
Has anybody got any suggestions for finding something better?  I'm looking for an 8.75:1  +20, or +30.
In fact while I'm pestering, a source for an SS90 cam would be very welcome too.

Many thanks

4
Singles / B40 Front Hub
« on: 30 August, 2017, 13:21:59 »
Hi Folks,
             I'm new here and have what's probably a very novice question, though I did do a search first and couldn't find anything.
I've just acquired a 1962 B40, which I intend to rebuild as an Enduro. I'm not too fussed about counting rivets etc. as it's going to be a primarily road bike (with a bit of green laning), so a few minor anachronisms (e.g. 12v electrics and electronic ignition)are OK by me. Sorry if that offends the purists.

I've managed to find a single sided front hub but, from my perusal of Rupert Ratios tomes I gather that it normally utilises a screw in wheel spindle.
Does that mean that I have to find a suitable fork leg to accept it, or is it possible to fit a different spindle that will match my original (clamp on) legs?
Many thanks

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