Superblend Bearings, general questions, advice, etc.

I am going to be starting to reassemble my '71 750 Commando. Right now I am going to focus exclusively on the crank. I'm going to be using superblend CN bearings on the crank and std. bearing shells on the big ends. All measurements are normal and well within tolerances.

My understanding is that the superblend bearing are two piece. One presses onto the crank, the other presses into the crankcase. I assume that standard heating and cooling techniques are sufficient to install. Is there any critical distances one should be aware of? Are there any installation tips that anyone has?

The big ends of the crank measure 1.750" with a micrometer. My best guess is that std sized shells should work just fine. I am going to use new bolts. Any advice there?

Superblend is a marketing term for a heavy duty roller bearing, SKF add an E to their number to identify it as heavy duty. The interference fits are within the normal heat range ie 150c or so. C3 is the current Andover Norton internal clearance provided, which slightly looser than CN.

Well, you will need to check endplay with the crankshaft installed in the cases. There seem to be varying opinions as to how much clearance is needed, but you can search here for some light reading on the topic.

Plenty of written advice about changing main bearings around. Only use C3 clearance bearings, best source is AN, and don't get concerned that they are made in India, they are the best available.

Advice is easy enough to find. Search this forum and be prepared for overload.

Yes, the inner section of the bearing is pressed onto the crank. More importantly the old one needs to be pulled off with a large puller, heat doesn't help here, and don't choose the cold chisel method. I use an oven to heat the cases for extraction and fitting of the outer bearings. A big puller to remove inners, and an old dressed inner as part of my tool to drift inners on. You can chill the inners, but avoid condensation forming on them.

You need to choose the style of shims you want to use to set end float, which is the critical measurement you don't seem to be aware of. Plenty of advice on that too and how to measure it.

You can shim with standard AN shims behind the bearing inner, preferably on the timing side. Norman White's book will cover that. If you choose that method a good idea is take one of your old bearing inners and dress the inside so that it will slide on to the crank. Use this in trial assembly to measure end float.

If you choose the bearing shimming in the case behind the outer bearing, you need to source suitable shims, VW crankshaft shims are suitable. To do this assemble with no shims, measure end float and shim to suit.

What clearance? Advice varies but Norton manuals and several posts on here cover that essentially:


So, since my motor is a short stroke race motor which recently span up to 8400rpm, I am using outer bearing VW shims set with 0.015" as guidance.

For several years this crank was shimmed with AN shims behind the inner race, with end float around 0.012" it's difficult to know if there is any difference. Jim Comstock says he has seem AN shims squeezed out, but that will be very extreme circumstances.

Then of course there is the big end, you don't mention measuring ovality. Have you measured big ends with a micrometer before?

Best gauge of big end clearance is Plastigauge. Put it on the crank under new shells, properly torque the rod, don't turn it, remove rod and measure the width of the Plastiguage. One box is a lifetime supply!

SteveA said:

Yes, the inner section of the bearing is pressed onto the crank. More importantly the old one needs to be pulled off with a large puller, heat doesn't help here, and don't choose the cold chisel method. I use an oven to heat the cases for extraction and fitting of the outer bearings. A big puller to remove inners, and an old dressed inner as part of my tool to drift inners on. You can chill the inners, but avoid condensation forming on them.

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Note that a '71 model should have a ball bearing on the timing side and an MRJA30 roller on the drive side with the roller race captive on the inner race but agree that C3 is probably the better choice for the 'Superblend'.

L.A.B. said:

Note that a '71 model should have a ball bearing on the timing side and an MRJA30 roller on the drive side with the roller race captive on the inner race but agree that C3 is probably the better choice for the 'Superblend'.

Andover Norton - CRANKSHAFT MAIN BEARING NJ306-E-XL-M1-C3#N1 (NM17822/4) FAG Schaeffler - 06.4118

CRANKSHAFT MAIN BEARING NJ306-E-XL-M1-C3#N1 (NM17822/4) FAG Schaeffler

andover-norton.co.uk

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'Originally had' a ball race, and a roller as you describe, understood, and of course this will be correct. And this deals with side loading/location without the need to set end float.

I doubt many still have a ball race? Though I do know a certain Norton 'specialist' preached their use for decades. He preached to me personally when I already had a new set of MkIII cases /crank, and a pair of factory roller bearings in my hands.

I bought a 1970 Fastback in 1974 and when I stripped it to race prep it, it had 'Superblend' mains rollers fitted. The previous (original) bearings had definitely had a going over with the cold chisel, which left a mark that tended to tear drive side oil seals!

Yes of course it's possible it's not the first change of bearings it's had.

SteveA said:

Only use C3 clearance bearings

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Admittedly, my only experience using C3 bearings was ordering them by mistake for a Triumph 650 that I rebuilt. I was astounded by the amount of "slop" in the crank and switched them out for CN bearings. Ran great. This Commando is going to be used for daily reliability and not high performance. I do not wish to give the impression that I am questioning the wisdom of those who are FAR more knowledgeable than I....but could you possibly give me a brief explanation why loose C3 bearings are preferable?

Banzaibob816 said:

Admittedly, my only experience using C3 bearings was ordering them by mistake for a Triumph 650 that I rebuilt. I was astounded by the amount of "slop" in the crank and switched them out for CN bearings. Ran great. This Commando is going to be used for daily reliability and not high performance. I do not wish to give the impression that I am questioning the wisdom of those who are FAR more knowledgeable than I....but could you possibly give me a brief explanation why loose C3 bearings are preferable?

Click to expand...

C3 bearings handle crankshaft flexing better at high RPM and possible crank misalignment (if it's not trued up perfectly when bolted together).

L.A.B. said:

Post in thread 'C3 vs CN'

Oct 30, 2011

Gentlemen,
The reason why Andover Norton switched from standard bearing spec. to C3 was that all bearing manufacturers now work at the lowest possible tolerance within the norm. In the old days they tended to be at the other side of the scale, manufacturing techniques being more "liberal" then.
The problem first became apparent to me with the C2 bearings Triumph specified for the T140 engines (part # 70-2879), in that if one used those lower-than-normal tolerance bearings the crank would not turn as soon as bearing and crankcase had cooled down (I deal in Triumph spares in my German firm...

• ZFD

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For another application, is there a version of this bearing that measures 25mm x 52mm x 18mm ?
Thanks

Banzaibob816 said:

Admittedly, my only experience using C3 bearings was ordering them by mistake for a Triumph 650 that I rebuilt. I was astounded by the amount of "slop" in the crank and switched them out for CN bearings. Ran great. This Commando is going to be used for daily reliability and not high performance. I do not wish to give the impression that I am questioning the wisdom of those who are FAR more knowledgeable than I....but could you possibly give me a brief explanation why loose C3 bearings are preferable?

Click to expand...

I am by no means an expert on this but a good friend who is and has built many Norton engines over the years told me that firstly what is considered a C3 clearance has seemed to him to have tightened up over the years. Secondly if installed with the correct crankcase and crankshaft clearance a tighter clearance bearing seems a little tight to him. Perhaps not true when warmed up but that's his experience anyway.

One thing he also does is machine a small relief on the inner race so a bearing puller can be used the next time around. He also has an old inner race with ground extra internal clearance for measuring end float as described above. Actually correction added later. I think it's the outer race so he can add shins behind the outer race.

He used to be the fitter and technical adviser for British Spares down here in NZ for many many years and has dealt with and sold hundreds perhaps thousands of bearings and this is his experience.

I have personally used the Andover supplied Indian made bearings on both my race and street bike with never any issues.

A friend assembled his 920 Maney crankcase with standard bearings believing that they were C3, but incorrectly supplied. Crank did not spin freely. Pulled it apart, wrong bearings, installed correct C3 bearings and no problems. Has now done several track days with it. Graham

also measure the bore the bearing is going to go into and measure the od of the bearing to make shure you have the proper pinch fit.

Mofosheee said:

25mm x 52mm x 18mm

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nup2205-e-xl-tvp2-c3-fag

If you're going to shim for end-float, I recommend shimming between the case and the outer race.
Some shim between the inner race and crankshaft. I don't think this is a good idea as, if the shim becomes free to move, it can wear a stress-raising groove in the shaft - VERY bad.
Cheers

SteveA said:

You need to choose the style of shims you want to use to set end float, which is the critical measurement you don't seem to be aware of. Plenty of advice on that too and how to measure it.

You can shim with standard AN shims behind the bearing inner, preferably on the timing side. Norman White's book will cover that. If you choose that method a good idea is take one of your old bearing inners and dress the inside so that it will slide on to the crank. Use this in trial assembly to measure end float.

Click to expand...

The story:

The motor that was in the bike was not "numbers matching." It was also in bad shape inso far as the pistons were both seized due to it being bored about .003" too tight....so it needs rebuilding. In the parts lot that I got with the bike was the "numbers matching" cases....with a couple of holes bashed into the left side where the connecting rod disintegrated and went through. I had that repaired and am now going to reassemble a perfect "numbers matching" bike. (Best laid plans....)

When I disassembled the donor engine there was a ball bearing on the timing side. I inquired with a trusted machine shop that specializes in British motorcycles and has done work for me in the past and he stated that if you use Superblend bearings in both timing and drive side it eliminates the need for shimming the crank. Did I hear him right? My understanding about the Superblend bearings is that they are superior in every other regard as well as eliminating the added level of complexity of shimming.

Again....I will concede ignorance and lack of understanding up front. Not sure I heard the guy correctly now.

Banzaibob816 said:

Did I hear him right?

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No, its the ball bearing that locks the crank to the timing side and removes the need for shimming. With 2 rollers as both float then the crank can move from side to side which the shimming reduces. I would not shim unless the end float was above 25 thou, its a whippy crank IE think of a skipping rope and too little end float can mess things up.

I think most over think things with shimming, our cranks seem to like a bit of end float, I have rebuilt a few Commando motors including mine and have never used shims for end float on the cranks and my own had about 24thou and its still running great, the motors I had built for friends and for friends of a friend they are all still going and everyone had end float.
Once I got a 750 motor that was rebuilt by the owner they shimmed the end float on the crank after taking advice from others then when he button it all up things went tight and thought he did something wrong was his own bike that he put the motor back together for the first time, he asked me to pull it down to find out what was wrong, the crank moved ok I started to pull it apart, had to remover the new bearing to find it had been shimmed, remover the shims and put it back together without any shims, that was just over 15 years ago and his Norton is still running, it didn't need shimming in the first place and it had about 12thou end float, he sold the bike not long after I put it back together but I know the person that he sold it to, but in the last 15 years it only gets ridden a few times a year so still low miles on the motor.
I had the chance to buy it off him but he was asking too much for it at the time.

Ashley