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mirpet
Level 1 Member
New South Wales
5 Posts |
 Posted - 22 Mar 2011 : 7:57:10 PM
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Hello All.
I've been browsing this forum for a while... time for my first post.
I'm rebuilding a CB350 race bike and have a query (which may be the first of many). I have read here and elsewhere about the mod to install bearings for the cam to run in... usually referred to as a "needle roller" bearing... but at times I see references to a 6004 or similar.
I've been told there's plenty of info on the Net about this mod... but for the life of me I can't find much in the way of detail. I think I read somewhere about having to mix an inner from one bearing with an outer from another... but that doesn't seem to make sense. Surely as long as the ID matches the cam's journal the housing can be machined to suit the OD... or am I missing something?
My existing cam & the "bearing" in the alloy end caps measure a shade under 22mm from memory (0.864") neither of which seems a "standard" size. I have double checked with a spare motor... same sizes. A 6004 ID is 20mm so that wouldn't seem to fit without machining something and unless I am missing something the OD of the 6004 (42mm) won't leave much metal in the alloy covers if they are machined out to fit. So perhaps a needle roller with it's smaller OD is more likely?
Can anyone shed some light on bearing sizes and types used? Photos would be good too.
Thanks very much for any advice.
Peter
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Edited by - mirpet on 22 Mar 2011 7:57:42 PM |
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racer7
Level 2 Member
67 Posts |
Posted - 26 Mar 2011 : 7:31:10 PM
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I have this needle roller conversion, but can't find my reference to what bearing sizes were used. The camshaft was turned down, and the camshaft end caps were machined. Neil Semple of Rising Sun Engineering
(part of Rising Sun Honda) has done a few. He's in Townsville.
Hope this helps. |
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mirpet
Level 1 Member
New South Wales
5 Posts |
Posted - 02 Apr 2011 : 7:17:30 PM
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| Thanks... I'll keep the option of turning the cam journals down in mind. |
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GD66
Senior Member
Western Australia
390 Posts |
Posted - 03 Apr 2011 : 11:56:39 PM
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| CAT Honda Classic Racing in UK does needle roller conversions. What you've mentioned about mixing the needle rollers with a different id sleeve is correct, but the numbers elude me for the moment. |
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jvdairlie
Level 2 Member
Queensland
48 Posts |
Posted - 06 Apr 2011 : 09:20:22 AM
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| Whatever else you do Peter - don't turn down the actual camshaft! The machining is done on the end caps only! |
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mirpet
Level 1 Member
New South Wales
5 Posts |
Posted - 06 Apr 2011 : 7:34:39 PM
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Yes James, I would be VERY, VERY hesitant to muck with the cam itself... although that does seem to be what was done in at least one case.
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Edited by - mirpet on 07 Apr 2011 07:29:04 AM |
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mirpet
Level 1 Member
New South Wales
5 Posts |
Posted - 07 Apr 2011 : 11:53:19 AM
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Hi again... at the risk of going on too much about this a few things I have picked up are:
* The bearing journal on both camshafts I have is just under 22mm, typically about 21.97mm. I am not a mechanical engineer but have seen reference to a clearance fit being in the order of 0.02mm at this diameter… so it would seem a 22mm ID bearing is the appropriate size.
* The way I had envisaged this mod being done was to fit a 22mm NEEDLE roller bearing into the existing end cap journals, it would just be a matter of having the housing machined out to the appropriate OD of 28mm or so, depending on the exact bearing type, and correct depth. (I have been sent a picture of this… but the guy couldn’t recall the bearing size).
* After checking with GD66 and JVDAIRLIE it became apparent the OTHER way this mod is done is to machine the end cap journals off completely and then fit a bearing into the cam box itself, where the end cap journals had previously been.
* The OD of these openings is 42mm and would be a direct fit for a 6004 (or similar) ball bearing… but these are 20mm ID and too small for the camshaft journals without having to machine them down or find a different inner for the ball bearing??? The photo of Ben's broken cam in the Saga series shows this type of bearing so obviously it can be done.
* The way the others said they had done it was to get a bearing that fits into the cam box (42mm OD) and a bearing that fits the camshaft (22mm ID) and mix and match the two to get the correct fit. I am just hunting through bearing catalogs to find appropriate sizes... may be possible using Needle Roller bearings but as yet I cannot find Cylindrical Roller bearings of the correct dimensions.
* I think another point of confusion (for me anyway) is that this mod is generally referred to as Needle Roller bearing conversion, hence my predisposition to think about the first option... whereas it seems cylindrical roller bearings may have been used by others?
Anyway… just wondering if anyone has any further comment on this mod? Like I say I don't want to go on about it, but would like to canvass a few opinions... and maybe leave some detail for others going down the same track.
Cheers... Pete
Oh, PS... I have a shipment of engine parts the way from Todd Henning Racing so will soon be into the rebuild. |
Edited by - mirpet on 13 Apr 2011 4:44:13 PM |
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matcho mick
Advanced Member
New South Wales
570 Posts |
Posted - 09 May 2011 : 10:04:48 PM
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mirpet,fit the 6004's,& machine cam shaft ends to suit bearings id,don't forget some endfloat,works for me!!, |
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racer7
Level 2 Member
67 Posts |
Posted - 21 May 2011 : 05:52:20 AM
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Hope your 'build' is going well 'mirpet'.
18 months is all (?) it took me to sort the wheat from the chafe, asking a million questions from a million people! And got a million answers! At the end of the day, I went 'sort of' my own way, thought I'd stuffed up, until a friend sorted it in his backyard! Truly! Applicable to myself, is one of our Members Signatures ..... 'a fool complicates the simple ......' Yep, 'twas me alright
racer7 |
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mirpet
Level 1 Member
New South Wales
5 Posts |
Posted - 22 Jun 2011 : 10:12:52 PM
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I am just about to get the engine reassembly underway, the last thing to do is take my camshaft and housing to my machinist this weekend.
I ended up sourcing two sets of bearings... one to do the mod by fitting the bearing INTO the existing end cap boss. For that method the bearing I chose is an NKJ22 which is a 22mm ID needle roller bearing with inner ring. The OD is 34mm so it will fit into the boss which is 42mm OD. I had the option of an NK22 which doesn't have the inner ring so this would have meant the rollers were running directly on the camshaft which could lead to premature wear.
The other bearings are NKS28 which has a 42mm OD and therefore fits AFTER the end cap bosses are machined off. These require a 22x28mm inner ring. I reckon this is the bearing JVDAIRLIE and GD66 were referring to.
As racer7 says ask a million people and you get a million answers, none of which is necessarily wrong... yes some may be better than others or maybe better suited to individual circumstances but in the end it'll just be a matter of making a call and sticking with it for better or worse... in the end I'll rely on the judgment of the machinist and weigh up the pros and cons of each method. As it turns out he has a history of racing Honda 350s so he could well be a good source of advice.
I'll let you know which way I go.
Pete |
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Topic |
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Camshaft Bearing Modification
