Clutch bearing/clutch centre fit?

I pulled my primary off to replace the rotor the otyher day and noticed my clutch basket seemed loose on the mainshaft. I pulled it all off and have found the clutch bearing to be only slightly worn, the problem is being compounded by the fit of the bearing on the clutch centre. The clutch centre is 34.9mm and the bearing inner diameter is 35.2mm. The clutch centre was a new one I had put on by someone else about a year ago, it may well have been like this since then and I've only just noticed it, but there is a LOT of movement when it's on the shaft. Has anyone else had this problem? I'm going to get a new bearing but do I need to replace the clutch centre as well!?

Headfullofsnakes said:

The clutch centre is 34.9mm and the bearing inner diameter is 35.2mm. The clutch centre was a new one I had put on by someone else about a year ago, it may well have been like this since then and I've only just noticed it, but there is a LOT of movement when it's on the shaft. Has anyone else had this problem? I'm going to get a new bearing but do I need to replace the clutch centre as well!?

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Is the clutch bearing the correct reduced clearance "one dot" or C2 type?

Hmmm dunno? It's an SKF 6007-2RS1

Mine was sloppy too. It had a ton of play, wobble or whatever you call it. I bought a new clutch center, bearing but have yet to fit it as the whole bike is in parts waiting for the frame to be straightened. I'll put my clutch center on the clutch basket tomorrow and get back to you.
There is some slop from the c-center to the main shaft. It only has a small c-clip on the end of the main shaft.
Not the best design.

As LAB indicated, the proper bearing is not just the typical off the shelf item.
Once installed it is an unusually close running clearance between the balls and the races.
The od, id and width will all be standard fits when measured with common tools..
I recommend you obtain the correct item from an OEM supplier such as A/N and order by the proper number.
It is the only place that offers the close tolerance that I could find. Yes, it is much more costly than the average electric motor bearing.
All the best.

Headfullofsnakes said:

It's an SKF 6007-2RS1

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If it isn't marked "C2" then it's probably a standard clearance bearing (2RS1 = double rubber seal-reinforced)

Headfullofsnakes said:

The clutch centre is 34.9mm

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I have just checked an old centre and that was dead on 35mm.

My clutch drum is pretty sloppy on the bearing too and I was thinking about replacing the bearing. Original for 14K miles. Never heard that it was a C2 bearing. I think we're talking about 06-0750? So it's a 6007 C2? Sealed or not doesn't matter much as far as I can see.

Dave
69S

Hi Dave,
yes, that is the number 06-0750.
The one I have is marked PORTUGAL 6007 FP as well as a reference to cigarettes or disparaging remarks to manufacturers gender preference, ha ha, not that there is anything wrong with that.
I can post pics of the bearing if you need to see it up close and personal.
Nowhere on the bearing is anything specifically marked C2. There are no other markings of any kind on the reverse side.
This is from an early production MKIII. I believe it is OE though have no proof either way.
The bearing does a lot of work when the clutch is disengaged and is in there all alone so the precision is logical.
An ordinary clearanced bearing will work too, it's just that the manufacturing lot will have some drift towards tight and loose ball clearance and the looser ones will allow the sprocket to deflect to a greater degree than the closer ones. Not a show stopper.
All the best.

The techinal data sections of both the 1970-'73(&'74) and 850 Mk3 factory manuals include the following information:

Clutch centre bearing specification: Deep grove(sic) ball bearing - one dot OD 62 mm, ID 35 mm, Width 14 mm Corner rad 1.5 mm

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Headfullofsnakes said:

I The clutch centre is 34.9mm and the bearing inner diameter is 35.2mm. The clutch centre was a new one I had put on by someone else about a year ago, it may well have been like this since then and I've only just noticed it, but there is a LOT of movement when it's on the shaft. Has anyone else had this problem? I'm going to get a new bearing but do I need to replace the clutch centre as well!?

Click to expand...

The center should be a press fit into the bearing. I got a new clutch center last year that was machined incorrectly. It was a loose fit. I sent it back and got a new one that was a press fit. Yours sounds very loose, it's going to wobble. The bearing manufacturers make bearings in different clearances so you can get the ideal running clearance in different setups. Two press fits. One press fit, one slip, ect. So the center is not only loose in the bearing but the interior dimensions inside the installed bearing are also looser than spec too.

L.A.B. said:

The techinal data sections of both the 1970-'73(&'74) and 850 Mk3 factory manuals include the following information:

Clutch centre bearing specification: Deep grove(sic) ball bearing - one dot OD 62 mm, ID 35 mm, Width 14 mm Corner rad 1.5 mm

Click to expand...

clutch-basket-play-and-gearbox-problems-mk3-t1629.html

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Absolutely correct LAB. It's in the book alright.
"one dot" could easily be overlooked/misunderstood/dismissed by a US reader.
The looser item won't leave anyone stranded but right is right.
All the best.

rpatton said:

The center should be a press fit into the bearing. I got a new clutch center last year that was machined incorrectly. It was a loose fit. I sent it back and got a new one that was a press fit. Yours sounds very loose, it's going to wobble. The bearing manufacturers make bearings in different clearances so you can get the ideal running clearance in different setups. Two press fits. One press fit, one slip, ect. So the center is not only loose in the bearing but the interior dimensions inside the installed bearing are also looser than spec too.

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YAHTZEE!

This is directly addressing the original poster's problem, clutch center shaft too lose fit in the bearing, NOT the bearing's internal clearance.

Should be a light press fit when all is correct.

It seems we finally getting to the point of the original post, ie the clutch centre is loose in the bearing ID.
I had this problem about 15 years ago and thought to rectify it by buying a new centre. I got it from Mick H and hence I'm guessing it would have been a AN part. Maybe not ,since it was a longtime ago. The new part was also loose in the bearing. I assumed that all the new ones were being made like that. ( the aluminium ones from Mick H were a tight fit in the bearing) I attempted to make it work better by using loctite bearing fit but it was never successsful for very long. I was using this clutch in the race bike with a belt drive. After a couple of years I did something about it by machining a new clutch spacer that butted up to the mainshaft circlip at one end and had a counterbore on the other that allowed it to go over the nose of the clutch cemter and butt up against the bearing inner race. This then trapped the bearing inner and held it tight aginst the inner face of the centre. Not sure if this would work on a road bike with an inner primary cover.
I went to this mod since I thought all the available clutch centers would be undersize.
Hence I'm really interested other people's experince and to hear if the clutch centers are now being made to the correct dimensions.
As far as I'm aware ( and I could easly be wrong) all the bearings of a nominal size will have the same ID and OD regardless of the clearance designation, ie the clearance is referring to the bearings internal dimensions not the external ones. As stated above, it shouldn't matter what bearing you have, the centre should still be a tight fit ( light interference or push?) on the centre.

SeeleyWeslake said:

Hence I'm really interested other people's experince and to hear if the clutch centers are now being made to the correct dimensions.
As far as I'm aware ( and I could easly be wrong) all the bearings of a nominal size will have the same ID and OD regardless of the clearance designation, ie the clearance is referring to the bearings internal dimensions not the external ones. As stated above, it shouldn't matter what bearing you have, the centre should still be a tight fit ( light interference or push?) on the centre.

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The short answer as to whats being made now is that some are and some are not the correct dimension. I had the numbers on the size of the center's bearing surface, old, new and second new but I can't lay my hands on them right now. Taking out the old one and putting in the correct new one required a hydraulic press.

You're right, the nominal dimensions of the ID and OD of the bearings don't change and are held to narrow tolerances. The variation of the internal clearances available under the different designations is to take into account whether there are interference fits on the shaft, the housing, or both; and by how much. The crush and stretch of the races will change the clearance in the bearing when it is installed.

Seems like it would be possible to shim this. Maybe not easy, but possible. 0.2mm is within a few ten thousandths of .008 inches. If you were to wrap .004 shim stock around the center? That is about the thickness of a pop can fwiw.

Russ

Look up the recommended bearing fits.
The bearing id, od and width are standard here.
A light interference fit is required in the application.
Both races should be witnessing diametral interference.
To disassemble originally all that is needed is a small plastic dead blow hammer.
To assemble heat the bearing and fit to the chilled center, heat the sprocket and fit to the bearing.
Sans heating, a 1 ton arbor press with some care and the appropriate supports should be more than adequate to assemble.
The point is that the hub bearing sprocket assembly should definitely not just fall apart without assistance once the ring is off.
A word of caution when measuring and reporting bearing and bore sizes-- tenths can matter, so also consider the measuring tool wear and calibration date.
The OP's 0,1mm loose is a dead cat fit not suited to the application. Shimming is not a long term solution. Get the correct parts. Go riding with confidence.
All the best.

Thanks for all this info. I have a new bearing now, I got it from British Spares here in NZ. They measured the ID before sending it and said it was 35 bang on. I haven't put it back together yet, I'm still unsure about the center... they're bloody expensive and I've barely ridden on this one! Wish I could send it back, but it is 'used' now eh. Bugger.

Just to add to the bearing thread, I got the bearing, 060750/S, from Old Britts today, 6007 2RS C3 EMQ. EMQ is a Chinese bearing manufacturer. Ella said the unsealed one they had was from UK, but at almost twice the price. I got this one for less than $15. I've seen them on line for around $7 including delivery. Now to take the primary apart, it's one thing I didn't deal with on my rebuild last year.

Dave
69S

DogT said:

Just to add to the bearing thread, I got the bearing, 060750/S, from Old Britts today, 6007 2RS C3 EMQ.

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A C3 bearing has more clearance than a standard (or CN) bearing?

Hmm, yes. According to the FAG bearing info I have, C3 is larger clearance than normal and C2 is less. I should call Ella and see what the UK bearing is.

Where is the information that specs the 060750 as a C2 or 'one dot'?

Dave
69S