Very tight main bearings?

Hello all...I am rebuilding a 72 Combat engine and have installed FAG NJ306E mains. I went to check crank end float and zero. I had placed .003" shims behind the inner race both sides hoping that would bring it close after reading heaps on the issue on here and other forums. I started to separate the cases and found with at 2mm gap in the cases still no end float! I have since separated the case halves and found that the new mains are very tight particularly on the timing side. So tight in fact it was quite difficult to remove the crank from the cases/bearing. I note these bearings are made in India and have a plastic cage. Could they be inferior?

The outer bearing races dropped into the cases with just some heat. Inner races required heat and seemed to slip on normally without any huge effort.

So any suggestions as to where to from here would be greatly appreciated.

Thanks
Mark

If you have FAG bearings with a plastic cage made in India, then there is a good chance they are fake or you have been sold the wrong specification bearings - Schaeffler who own FAG bearings have this style of bearing made in India have brass cages for this part.

Madnorton said:

If you have FAG bearings with a plastic cage made in India, then there is a good chance they are fake or you have been sold the wrong specification bearings - Schaeffler who own FAG bearings have this style of bearing made in India have brass cages for this part.

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Not necessarily fake, as the latest FAG bearings supplied by Andover Norton are made in India-however they are brass cage as you say, but are C3 clearance.

pierodn said:

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I've just bought a new FAG main bearing from my local bearing shop, and I've just checked it and am slightly surprised that it also says "India" on it's circumference, but one I bought about 4 years ago doesn't.

Exactly, not sure if they make the actual 'plastic' cage bearings of this type in the Indian production plant, and so could be possibly fake. If it is, what is the world coming to - fakes of Indian products, says something for the quality of the Indian made product.

Madnorton said:

Exactly, not sure if they make the actual 'plastic' cage bearings of this type in the Indian production plant

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http://www.ebay.at/itm/1-St-Zylinderrol ... 1e8dbb8711


The Polyamide NJ 306E option has been available for many years so any suggestion of a fake just because it happens to be made in India and has a poly. cage seems to be pure speculation. The fact that the bearing is tight is probably more to do with the bearing being standard clearance (rather than C3) I would think?

Edit: FAG data sheet deleted (it was for NJ203E TVP).

L.A.B. said:

Madnorton said:

Exactly, not sure if they make the actual 'plastic' cage bearings of this type in the Indian production plant

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http://www.ebay.at/itm/1-St-Zylinderrol ... 1e8dbb8711


The Polyamide NJ 306E option has been available for many years so any suggestion of a fake just because it happens to be made in India and has a poly. cage seems to be pure speculation. The fact that the bearing is tight is probably more to do with the bearing being standard clearance (rather than C3) I would think?

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+1 on your conclusions Lab. IMHO this is why its always worth paying an insignificant amount more to buy from a proper source like AN, unless you are a fully competent engineer buying from an equally competent bearing provider.

FAG has a factory in India, 100% owned by FAG, and this is the only place in the world where FAG currently make this bearing with brass cage. We have not had any quality issues with this bearing. And no way could we buy a bearing for the sum in the given link, but then that is a) plastic cage and b)wrong clearance. Or a no-name bearing.

Quite a few years ago now Mick Hemmings and my local engine man Rudi noticed- independently- that the original spec was too tight all of a sudden so cranks would not turn in the crankcase. My layman explanation is that with improved manufacturing methods bearing manufacturers moved to the bottom of the clearance scale specified in DIN for the bearing. Hence we have since supplied C3 spec. Needless to say nobody else complained....

Plastic cages are high risk- not immediately, but as the plastic ages by the constant changes in temperature in the crankcase bordering on the temperature limit of a plastic cage it gets brittle. If my engine man Rudi finds them in an engine he routinely puts propper ones in.

Coming back to the clearance question, Triumphs specified C2 (less clearance than STD) for the drive side main bearing on 650s and 750s. We found the same phenomenon there around the same time (I have done Triumph spares in my German shop for over 35 years). We have since supplied STD clearance instead of C2 for Triumphs.

Joe/Andover Norton

You can lap the bearings to get proper clearance. It's getting tough to find some bearings in c3 clearance, so instead one can used a mandrel and adjustable lap to change c normal to c3, or really to custom fit the bearings. This procedure also ensures that the main bearing bearing outer races run true to the centre line of the mainshaft and remove flat spots on the outer race which may be there after shrinking the bearing into place. In other words, it restores the outer race to a circular shape.
I had to get familiar with the process when building my Vincent Special engine as C3 bearings were not available for that crank. I learned that the lapping mainbearings with mandrel and lap is standard procedure for the top Vincent engine builders.

Glen

ZFD said:

Coming back to the clearance question, Triumphs specified C2 (less clearance than STD) for the drive side main bearing on 650s and 750s. We found the same phenomenon there around the same time (I have done Triumph spares in my German shop for over 35 years). We have since supplied STD clearance instead of C2 for Triumphs.

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The factory fitted both types during T120-T140 production-but without any change of bearing part number (E2879/70-2879). :roll:

http://www.classicbritishspares.com/blo ... -clearance

The preferred standard (CN) clearance bearing is available under Triumph[Edit: BSA] part number 68-0625. :wink:

I thought the C designation was the running clearance of the rollers (or balls if it was a ball race) Lapping the hole in the centre race will not change the C designation of the bearing just the size of the hole. Or am I missing something here?

gripper said:

I thought the C designation was the running clearance of the rollers (or balls if it was a ball race) Lapping the hole in the centre race will not change the C designation of the bearing just the size of the hole. Or am I missing something here?

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Glen was talking about lapping the bearing surface of the outer race, not the hole in the inner race.

Ken

lcrken said:

Glen was talking about lapping the bearing surface of the outer race, not the hole in the inner race.

Ken

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But even so....

gripper said:

I thought the C designation was the running clearance of the rollers (or balls if it was a ball race) Lapping the hole in the centre race will not change the C designation of the bearing just the size of the hole. Or am I missing something here?

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The bearings inner race expands when it is press fit on the shaft and the outer race is compressed when it is fit in the case. Incerasing the ID or decreasing the OD will affect the rollers clearance.

I have run race engines with very tight main bearings when cold with no problems. As the case heats to normal operating temperature, the bearing is no longer compressed in the case so the bearings roller clearance grows also. Jim

I had exactly the same experience as Mark when building my engine with superblends a few years ago (Cn, supplied by Norvil).
From memory, I think I did a trial assembly and they seemed ok, but after adding a smear of bearing loctite for final assembly they were too tight. The loctite was enough to eliminate any clearance!
Then I learned that, as Joe says, Andover now supplies and recommends C3 bearings.
I sourced some C3 FAG bearings locally in Australia (made in India), problem solved.

The bearings are C3 clearance and were obtained through a large bearing retailer near where I live. So I don't think they are fake considering some of the responses here.

How much pressure should be applied trying to measure the end float ie levering the crank with considerable force or should it slide by hand pressure?

Should I be concerned about the polymide cage and cut my losses and get the brass cage version considering the longevity of the engine? I struggle to understand why this cage would be offered if the longevity of the cage COULD be problematic??

Does anyone have any solid evidence of the polymide cage failing?

Many thanks for the responses so far.
Mark

I use polymide cages in all my BSA Unit Singles rebuilds and not had an issue yet, I leave the primary seal out to breathe through the primary case and get to see the cage if i take the clutch off and not seen any change. Never had to replace mains in a Commando but if I ever did I would use them.

I believe the crank should slide by hand pressure. One thought: were there any score marks on the crankshaft? I removed some from mine before fitting the inner race.

The preferred standard (CN) clearance bearing is available under Triumph part number 68-0625.

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68-0625 is not a Triumph part number- Triumph never used the 68- prefix- it is the number for the BSA A65 main bearing. I sell the STD clearance bearings under that number.

I am having the same problem with the bearings I've fitted (FAG NJ306E.M1) also made in India, brass cage. These were supplied by Britishspares in NZ. I have no lateral movement at all with the crank installed in the cases. Had .020 with my old bearings from the same supplier with the same serial #'s also made in India.
Am going to split the cases again and take a look see. They were very tight during assembly. Have we got a bad batch of bearings? At aroind $A100 a bearing thats a real pain.
jug