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#539898 04/25/14 11:06 pm
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Hi,
It is correct to say that the bearings used in the engines of most old British motorcycles should have a 'C3' or as used to be known as '000' rating?

The Brit bike dealers just seem to be flogging anything they can make a quid on!

When I spoke to a major distributor of spares they told me that was no specific bearing clearance when referring to bearings in the original parts list, for example in BSA parts lists and service sheets.

Having taken some old bearings out of some very old engines i do not see the '000' mark very often, was this clearance the the standard in the day?

However, as i am 51 i don't go back that far, but all the 'old timers' i know say they only ever fitted bearings with '000' clearance and this gave the right 'fit'.

looking the the nomenclature for modern bearings, C3 is the internal roller or ball clearance NOT the 'fit' or even 'precision'.

Advice from a Mechanical engineer or others would be grateful.

mike.


Mike.



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C3 is a good fail safe for a steel bearing fitted within an alloy case with an interference fit, however its best to check the original as Triumph fitted CN mains during some periods.

A good supplier with supply the proper clearance as long as you order by part number, the BSA lists do not mention it in the tables but the dealers knew. Again there are problems especially with Triumph using the same part number to cover a period with 2 clearance fitted.

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The bearing "Class Fit" information I use was compiled and supplied to me by Jack Shortland. Who was Jack Shortland?

Jack Shortland was the Export Spares Manager for Triumph. When Dennis Poore sold Factory #2, which held all of the spares for a production run of TR5T models, to the Danish Triumph Distributor, Buster Reinhardt. Buster set up Jack to become the Managing Director of a company they called PS Motors. The "S" was for Shortland and the "P" was for Price. Yes, the same Brenda Price that started in the factory office at 17 and ended up running the U.S. operations for the Triumph Co-operative.

As spares were always short it was important for a distributor to have more than a working relationship with the factory and Jack and Buster became close friends. Having a friend in the office never hurt and Brenda would be invited to spend the production break time in August staying with the Reinhardt family in Denmark.

Buster sold PS Motors, including the #2 factory site, to David Holder. David was the son of Matt Holder who was the Scott enthusiast and ran a company that made a lot of parts for the original W.E. Wassell called Aerco. Matt is the guy who went around buying up old motorcycle manufacturers like Scott, Velocette, Royal Enfield and Vincent. Along with the PS Motors stock and trade was Jack. He continued to work for David until his death some 10 odd years ago.

Jack was a man immersed in details and organization. His card index was the source of all sorts of information. He was one of the people behind the Wall Poster showing all of the gear interchanges, which he admitted, on the the day it was published, at best, still a work in progress. Jack had also developed a close working relationship with many suppliers. One was RHP and this relationship continues today.

Quote
It is correct to say that the bearings used in the engines of most old British motorcycles should have a 'C3' or as used to be known as '000' rating?


The simple answer is no. There are many factors that go into the selection of pre-fit bearing clearances. While we look at a bearing as being solid hunk of steel, under pressure bearing steel will expand or compress.

Take the MJ1 1 /8 ball bearing used both the timing side of a Triumph 650 (C3 condition) and the drive side of a T150/A75 (CN normal condition). On the 650 the bearing is a press fit in the crankcase AND on the crankshaft main shaft (also there can be alignment problems from production) so engineers allow extra clearance for compression and possible alignment issues.

On the T150 alignment isn't an issue as production tolerances have to be much better because of the two center main bearings, and while the bearing is still a press fit in the crankcase, it is a loose slip fit on the crankshaft main shaft.

With specifying pre-fit bearing clearances engineers are looking at getting specific fit running clearances once the bearing's inner race has expanded and the outer compressed.

Last edited by John Healy; 04/26/14 11:13 am.
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As Kommando says--C3 is a good fail safe.
FYI the C series designations for bearing internal clearance replaced the dot or circle designations---which themselves defined the bearing internal clearance.
To get the correct clearance first of all find out what bearing number and internal clearance you need.
To do this either:
a) Look at the old bearing. The number is normally pretty clear but the c, dot or circle designation is often very very faint. You often need to use a magnifying glass and get the light at just the right angle.
or
b) Ask on this forum for the correct internal clearance for your bike---the knowledge on this forum IMHO exceeds that of the normal Brit bike supplier. Use this C designation with the bearing number.
Then go to a bearing supply specialist (Brit bike parts suppliers are not bearing specialists) and ask for the bearing number and C designation. They will know exactly what you are talking about. And ask for a European (SKF etc) or Japanese (NSK etc) bearing--no Chinese crap. You might pay a bit more--but get a superior product and peace of mind.
And talk to the bearing guy--they are founts of knowledge if you get the right guy.
Interesting little aside--the last time I was in my bearing supplier in New Jersey I got talking to the guy behind the counter and he asked what I needed the bearings for. After I told him he said--"That is interesting--my mother moved to the States 55 years ago. Before that she lived in Birmingham and worked in a factory making carburetors for BSA". So with that link I know when I go back there next time I will get great service.
HTH

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I had time the other night to go through some paper I have collected over the years.

There was never a published reference to the change from a CN bearing on the Triumph drive side to a C2. I could never pry a time frame out of Brian Jones in the years he worked for Les Harris and we traded in the U.S. as "Triumph Motorcycles made under license." While he shared a lot of information with us, he never didn't give us a engine number or date when they made the change. This is the closet bit of information I have come across giving an idea of the time frame this was done. It is in a letter to a non-Triumph dealer who had mailed him about main bearing failures.

Brian Jones Letter

This would put the introduction of the C2 bearing about the beginning of the Co-operative, or the 1977 model year.

I though some of you Triumph people would be interested in seeing this.
John

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Thanks, John, very useful and interesting.


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