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Topics - Dabbist

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Singles / 7" tls brake
« on: 14 June, 2018, 16:23:15 »
I've seen something similar to this on the forum, but I don't think it's quite the same.
I've fitted a 7"tls front brake to my B40 and I'm using a tr25w cable, which seems fine for length, plenty of adjustment left in it. BUT...
If I set the brake up so that the shoes are just touching with the lever at rest, I can easily pull it all the way to the handlebar with two fingers.
The wheel locks up on my man cave floor, with very little movement of the lever, but i can't test it realistically as it doesn't have the engine in yet.
I've thought of shortening the actuator arm, but the geometry will only allow me to do so by 10 or 15mm before things start fouling and the cable run gets too kinky.
That'll help some, but not sure how much and it doesn't feel like it should be necessary.
Any ideas?


Singles / C15 centre panel
« on: 07 May, 2018, 22:02:49 »
My B40 has a C15 centre panel ( the one between the oil tank and the tool box) which has the original air filter welded in place.
I understand that complete ones are quite hard to find. I don't intend to use the original filter, so if anyone has a decent b40 centre panel ( exactly the same but without the filter) I'd be happy to do an exchange, otherwise  i'll just remove the filter, which would seem a shame.

Singles / B40 fork seal holder string seal
« on: 06 May, 2018, 10:06:03 »
Hi All,
           While stripping my b40 fork sliders, I found there's a "seal" of twisted string around the bottom of the thread for the oil seal holder. I haven't seen any anywhere and can't quite figure out how to twist it in place tightly enough. Has anybody out there made them (if so, how)  or would a big "O" ring do the job?

Singles / B40 Alpha main bearing conversion
« on: 27 April, 2018, 14:24:15 »
Hi All,
          Has anybody out there got experience of fitting the Alpha roller bearing timing side conversion to a B40?
Not being able to find any instructions anywhere I assumed it would be pretty straight forward. Since the whole thing readily comes apart, it seemed logical to fit just the outer ring and drop the rest in later.
I can now fit the centre into the rollers or the rollers into the outer ring, but not both. It will go in almost exactly half way with finger pressure, but no further.
I'm guessing I could pull it in with something, but don't want to damage it. Is my best bet to heat it up again, or is there a trick to it?

Singles / B40 Fork Bushes
« on: 23 April, 2018, 15:03:54 »
Hi Folks, 
             Having heard tales of pattern bushes having wortse clearance than old, worn ones I thought I'd make some to fit properly. My old ones look like some sort of bronze, but I've seen new ones advertised as brass. Does anybody know what they should be?  I'm guessing that it may not make na huge difference, since there's no high rotating loads involved.

Singles / B40 crankshaft balance
« on: 01 April, 2018, 19:02:51 »
Hi All,
I'm a bit baffled by my  first experience of trying to balance the crankshaft on my 62 B40. I've acquired a +20 high compression piston, so assumed it would be out a bit.
It seemed way off and in fact balances almost perfectly with just the gudgeon pin in place. Admittedly the new pin has 2 1/2 times the wall thickness of the old one, but that still leaves 367g of piston and rings to account for, which feels like an awful lot to be taking out.
There are already six big holes in the flywheel, though none quite opposite the big end.
Does anybody know whether this is truly excessive, or have any wisdom to offer?
Many thanks

Singles / Tappet Adjusters
« on: 16 February, 2018, 14:51:16 »
Hi All,
        Just a quick check to see if I've missed something obvious.  I've just bought a pair of tappet adjusters for my B40 build.
The site described them as being for Triumph T120/T140 and BSA A7/A10/A65.
They're the same thread as the original B40 ones and the same length, but have a mushroom head, rather than a parallel one.
Trying to visualise the geometry in my head I can't see where that would make a difference. Does anybody know of a problem with them in B40s, or is the advertiser just short in his listing?
Many thanks

Singles / B40 wheel bearings
« on: 11 February, 2018, 10:51:19 »
Hi Folks,  I have a pretty stupid sounding question but, discretion being the better part of valour and all that, I thought I'd ask it anyway.
I'm struggling to shift the front wheel bearing retainer on my '62 B40. The Haynes manual says it's RH thread up to 1970 and RR doesn't specify it. Mine is clearly stamped "LH". Of course there's no guarantee that it's the original hub.
Can anyone confirm that it means left hand, before I start to apply a lot of force to it?
Incidentally, if anyone feels the need to laugh at my ever present incompetence my mate convinced me to document the whole rebuild at it could at least be a cure for insomnia☺
Many thanks

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.

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 :-[

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

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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