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D3 crankshaft and bearings
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Landroll
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September 18, 2021 - 11:36 am
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Hi I am in the process of replacing the bearings and oil seals in the crankcases of a D3 but have hit a snag. The bearing inners are very tight going on to the crankshaft on both the drive side and the flywheel side. When reassembling the crankcases they crank does not slide easily easily into the bearing inner races and requires force to fit. I have already gone through a set of bearings trying to fit it all together due to the extra pressure on the inners. Does anyone have a method that works?

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sunny
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September 18, 2021 - 12:02 pm
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hi  Rick  it  sounds  like  you  have  chep  berings        ther  allways    dificalt  to  fit   ,    it  all  needs    woring    up  apart  from  the  crankshaft  wich  needs  a   compleat   checking    out   now  if   you  donot  have   the  kit  and  nowhow   its  best  to  take   it  all   to  someone   that  has   sorry   for  the  bad  news      but  dont  give  up   yet   

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Landroll
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September 18, 2021 - 12:26 pm
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The bearings I have are Japanese KSM which I thought would be ok. Come so far I will keep going until it gets there. Ah well.......

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FitzFortune
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September 18, 2021 - 1:07 pm
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Similar issues have ** Please log in to view **

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Sponge
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September 18, 2021 - 1:07 pm
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D3 was fityed with imperial bearings. Modern Japanese are metric ground to an infinate number of decimal places. Better too tight than sloppy. Try to get some NOS imperial bearings and give your crank lands a good clean up. Then I reckon if will go together nicely. 

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Landroll
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September 18, 2021 - 2:20 pm
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Thanks for the advice guys, never thought about the difference between imperial or metric tolerances. I will try and locate some NOS imperial bearings

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Ringting
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September 19, 2021 - 2:08 pm
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As above. I used Rex Caunt bearings, available from ebay shop. They are spot on, Slide on but no slop. You need this or you  can't set the crank end float and risk mis-aligning the crank if it takes a lot of force to squeeze the cases together. Well worth paying the extra for the fit and quality. Also make sure you get the oil seals in the right way round.

Alan.

D1, D14/4, Guzzi LeMans, Guzzi V35, Triumph Trident 900, Maserati 160 t4. Mk1 Mini Traveller, Berkeley T60.

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Sponge
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September 19, 2021 - 4:26 pm
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Hear hear above. I have never had any probs with Rex Caunt bearings. If you look after your engine and use good oil with regular changes they ought to be the only main bearings you will ever need to buy. 

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Rogereld
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October 25, 2021 - 2:24 pm
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Ringting said
As above. I used Rex Caunt bearings, available from ebay shop. They are spot on, Slide on but no slop. You need this or you  can't set the crank end float and risk mis-aligning the crank if it takes a lot of force to squeeze the cases together. Well worth paying the extra for the fit and quality. Also make sure you get the oil seals in the right way round.

Alan.  

What is the right way round for the oil seals.  I have been looking for some clear pictures or diagrams as I am ready to fit the 5 bearings and 4 oil seals in my D3 crank cases. (Purchased from Rex Caunt)

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sunny
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October 25, 2021 - 4:03 pm
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hi   Roger     the   standard  is  that  all   seals  are  fited   with  the  seal  springs   into   the  centre line   of  the  engine   or  wotever   ther   fited  to  that  makes    it  a  bit   harder   to  fit   coz  the  crank  seal   thin  edegs   of  the  seals   are  the  ones   thay  get  pushed  in  with   leaving   the  springs  looking  at  the crank  flywheel  webplates ., if  needed   do  the  end  float    be  fiting  the   seals  ,., the  rear  sproket  seal  is fited  likewize so  you  can  see  the spring  from  the inside  of   the seal holder 

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Rogereld
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October 25, 2021 - 6:31 pm
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Thanks. That is helpful. I have various engine assembly guides but none give much detail on the oil seals. Perhaps it was assumed knowledge at the time. BSA service sheet No 506 does not say which way round the oil seals should be fitted. A BSA Service Chart mentions the generator side oil seal should be fitted lip upwards outside the main bearings and flush with the outside face of the crankcase. Is the lip the flat surface or the inside with the spring? There is a photo on the service chart but not clear enough to see the detail of the oil seal.

 My Haynes manual (p27) says "drive the oil seals into their respective locations"  with no information on what the respective locations are.  I have searched for photos on this forum and found a couple in cocorico's photobucket but with inconclusive hints that one of the oil seals in a photo may be the wrong way round so the photos may not be a reliable reference. 

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cocorico
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October 25, 2021 - 8:39 pm
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Did you look in FAQs? ** Please log in to view **

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Rogereld
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October 25, 2021 - 9:53 pm
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cocorico said
Did you look in FAQs? ** Please log in to view **

Thank you.  Yes I did look in FAQ's and after scrolling down a couple of pages I found a thread titled  ** Please log in to view **  but it didn't seem to address the issue of which way round each seal should be.  

I have now read the other FAQ thread you have provided the link for, that I had not seen before. ** Please log in to view **

It has added confusion. In that thread Post No.2 says "The open side faces inwards."  It is followed by post No.3 which says "So just to clarify - if I have the crankcase halves laid out in front of me, each oil seal is placed into position with the lip going into the hole and with the flat side facing me."   That suggests the flat side of the oil seals should face the crankshaft which contradicts other advice I have been given.  Post No.7 says "In other words,the side with the spring should face the con-rod.."  Is that contradicting post 3?

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GlenAnderson
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October 25, 2021 - 10:11 pm
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Like Sunny has said. 

All the seals are fitted with their springs facing the centre of the engine. 

The inner ones are like that because crankcase compression is higher than the atmospheric in the gearbox. The outer ones are like that to keep the oil inside. 

The confusion arises because people think the inner ones are there to stop oil getting past into the crank void, but they’re not, they’re there to stop crankcase pressure escaping. 

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cocorico
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October 26, 2021 - 7:30 am
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Rogereld said
...It has added confusion. In that thread Post No.2 says "The open side faces inwards."  It is followed by post No.3 which says "So just to clarify - if I have the crankcase halves laid out in front of me, each oil seal is placed into position with the lip going into the hole and with the flat side facing me."   That suggests the flat side of the oil seals should face the crankshaft which contradicts other advice I have been given.  Post No.7 says "In other words,the side with the spring should face the con-rod.."  Is that contradicting post 3?  

Unfortunately, being merely a forum for enthusiasts, there are many contradictions posted, some of which slip into FAQs as part of the discussion. Add in the number of times this same question has been asked - and answered - and the lack of volunteers  to help monitor content, I would suggest that some posts should not be taken as gospel. Bearing in mind that fact, the age of the bikes and factory data, it is often a good idea to look for alternative sources of info. Though simple bikes, they require skill to work on them. If you search the net for info on oil seals, you will find plenty from their manufacturers on how to position and fit them. 

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Rogereld
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October 26, 2021 - 7:50 am
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I will fit all the oil seals with the springs facing towards the centre of the engine.

Apologies for raising a subject again that has been discussed before.

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stubaker58
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October 26, 2021 - 8:02 am
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Rogereld said
I will fit all the oil seals with the springs facing towards the centre of the engine

That will do it, succinctly put, well done!

“There’s nothing new under the sun”.

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Number6
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October 29, 2021 - 10:25 am
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GlenAnderson said
Like Sunny has said. 

All the seals are fitted with their springs facing the centre of the engine. 

The inner ones are like that because crankcase compression is higher than the atmospheric in the gearbox. The outer ones are like that to keep the oil inside. 

The confusion arises because people think the inner ones are there to stop oil getting past into the crank void, but they’re not, they’re there to stop crankcase pressure escaping.   

This is the clearest explanation I've seen. thumbs-up

Mike H --

Murphy's 4th law of motion states that any small object that is accidentally dropped will immediately hide itself under a larger object.

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