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Bruce's D1
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cocorico
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November 8, 2018 - 2:41 pm
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If you installed new bearings, it's possible that they have square edges - the cases are made for chamfered edges, so square ones 'stick out' a little.

1956 D3 awaiting a new magneto. 7 other bikes in the Barn, 6 runners and a still in progress Morini 250

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sunny
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November 8, 2018 - 2:50 pm
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hi    Bruce      yes   if  you  have  fited   new   brings  & seals    its  best  to   bild   crank & cases   for  each  new  item       newerns     always   play  up       as thay   tend   to  be  tuch   biger       well  done  anyway     as  i  think  you  are  on  the  rite  track   

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sunny
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November 8, 2018 - 3:09 pm
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hi  Bruce   i  like   the  ATOM   but  if  the  magnet rotor  moves   on the  sharft   the  timing   gos   out   so  i  up graded to  a  6 Vt baty & coil  igntion    so  if  it  moves  the timing   dont   move      , the  real tip  is to  get  the  motor started  with  its  old  system  first

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thornebt
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November 8, 2018 - 3:11 pm
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I bought the main bearings from Rex Caunt and I think they have chamfered edges.  It's these bearings:-

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I think they look chamfered in the photos anyway.

I'm a bit stuck about what to do now.  I could remove the oil seals (which I'll probably need to replace), heat the crankcases and try to tap the bearings in a bit more.  If they don't move at all then I still won't have enough endfloat.  I guess that this is the best way to proceed and see where I end up.  The bearings are 14.25mm thick but I shouldn't need to source narrower bearings should I?

Cheers.  Bruce.

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thornebt
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November 8, 2018 - 6:00 pm
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All is looking good now.  It was one crankcase that didn't seem to be going onto the crankshaft far enough so I removed the oil seal, heated up the crankcase and removed the bearing.  It definitely has chamfered edges and is exactly the same width as the old bearing.  I again heated the crankcase in the oven at 180C and the bearing dropped back in with a definite clunk - so it is as far home as it can go.  I also used the old bearing to give a few taps to the strange fan shaped oil flinger disc on that side of the crankshaft just to make sure that was fully on.

It went back together and crankshaft spins freely.  The only difference this time is that it's missing the oil seal.  I fitted the four shims on each side and it still spins perfectly.  I don't think the ThreeBond rubberised sealant will add anything to the endfloat.

So it's happy days.  Just need to get a replacement oil seal and I'll finally get the engine back together.  

Cheers.  Bruce.

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BSAdave
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November 9, 2018 - 10:06 am
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I use a atom unit and it works well, I carry the points in the tool box just in case, and the capacitor is left in place just in case the unit packs up, then it just a quick job to revert back.

I could agree with you, but then we would both be wrong

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November 9, 2018 - 12:49 pm
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Keep a lookout on ebay,I bought three from a seller the other year,ready for two projects,plus spare.

Blue

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thornebt
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November 9, 2018 - 4:10 pm
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Thanks Blue.  I'll keep an eye on Ebay.  The unit I have is brown but they come in different colours.  I guess that the other colours probably won't be suitable for the Bantam.  Cheers.  Bruce.

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BonesCDI
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November 9, 2018 - 10:45 pm
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The Atom module you want for a Bantam is the Brown Atom. The other colours are for differing dwell angles on the different engines they were suited for.

Atom still make gardening products but they have no intention of re manufacturing these units. The Late Chris Gamble told me he enquired about having them remanufactured and they agreed...……...only if he ordered 1 000 000 of them!

They do pop up from time to time on ebay etc as Blue said. If you also google Nova Booster it is basically the same thing.

Bones.

Running and project bikes from 1912 -2005..........She hasn't said stop yet.........

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thornebt
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November 9, 2018 - 11:14 pm
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BonesCDI said
The Atom module you want for a Bantam is the Brown Atom. The other colours are for differing dwell angles on the different engines they were suited for.

Atom still make gardening products but they have no intention of re manufacturing these units. The Late Chris Gamble told me he enquired about having them remanufactured and they agreed...……...only if he ordered 1 000 000 of them!

They do pop up from time to time on ebay etc as Blue said. If you also google Nova Booster it is basically the same thing.

Bones.  

Thanks a lot.  I'll have a look at the Nova Booster.  I basically want a spare unit just in case my Atom ever packs up.

Cheers.  Bruce.

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thornebt
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November 12, 2018 - 4:46 pm
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The engine rebuild has gone quite well so far.  This afternoon's job was replacing the worn small end bush.  So I rigged up a bolt and spacer thinking I'd wind the new bush out and the new one in behind it.  It didn't go well!  I managed to distort the new bush.  Anyway my barrel is at the engineers being honed so I phoned them and asked them to do the bush replacement job for me as soon as my new bush arrives from Rex.

I thought this would be an easy job but I'm not going to risk messing up a second bush at £14 each.

Cheers.  Bruce.

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mike p5xbx
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November 12, 2018 - 5:36 pm
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you do realise they have to be reamed to the correct size after fitting

D? - D10- D14 Bantams 350 AJS -500 Triumph http://bsanotru.....lfire.com/

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thornebt
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November 12, 2018 - 6:19 pm
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Hi.  Yes, I realise it will need to be reamed.  I used the same size adjustable reamer to ream the layshaft bushes.  That job went well.  Cheers.  Bruce.

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daveclough
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November 22, 2018 - 8:26 am
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I did the same, in fact on my c15 i got one bush stuck in a case side grrrrrr. Glad others face the same challenges. 

 

Dave

1966 BSA Bantam D7 - Bones CDi and Yamaha Clutch conversion.

A 1969 B175 - with Bones CDi, and new Amal MK1 Concentric

Another 1966 D7 which is presenty beng assembled.

My personal blog can be read at http://www.anot.....yvisor.com

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November 23, 2018 - 12:41 pm
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Stepped mandrel prevents crunching new bush during insertion.

Blue

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thornebt
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November 26, 2018 - 8:21 am
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I reamed my new layshaft bushes.  One bush allows the layshaft to turn but without any 'rock' in it.  The other is a tighter fit and holds the layshaft so it can't rotate.  I first thought that this was a good thing as the shaft doesn't spin round in operation.  But I'm now thinking that the shaft probably should rotate slightly in the bush to help gear engagement.

Can someone please confirm if the layshaft must be able to turn in the bush?

Cheers.  Bruce.

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sunny
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November 26, 2018 - 8:33 am
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most   bushes  must  have   a  GAP    for  OIL    this  is  about  one   thow      &   some  soud   have a   oil  groov  anyway   the  shaft   must   moov   or  it will   drag   the   bush     around   &  wear  away   the  aly   casing

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thornebt
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November 26, 2018 - 10:47 am
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My crankcases fitted together fine and the crank rotated freely.  However, when I inserted the main bearing oil seal on the timing side it seems that the crankshaft oil seal comes up against the oil drag fan and stops the crankshaft from turning.  There's clearly something wrong here as the internal lip of the seal is about 28mm, the diameter of the crankshaft is about 19mm!  

I must have the wrong oil seal?  This is really confusing!  Cheers.  Bruce.  DSCN0938.JPG

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thornebt
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November 26, 2018 - 11:01 am
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I'm a complete idiot!  I think I've worked out that the oil seal I've put in shouldn't be there at all?  There should just be the smaller oil seal on the outside of the crankcase.  The oil seal came in a kit for D1 engine but maybe it's only for D3 engines? 

But if someone would kindly confirm that I'd be grateful.

Cheers.  Bruce.

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November 26, 2018 - 12:52 pm
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That`s right oil fan is to fling mix out to the bearing....and it can`t do that with a seal in the way. 

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