No shims behind Super Blend Bearings

I dropped the bearings out of the cases on 850 Commando There were no shims behind the super blend bearings. I did not measure the crankshaft end play before taking it apart but there was definitely end play there. Now I'm not sure what to do or what the pupose is of the shims. Did they not set the endplay correctly at the factory? Manual says .005 to .015 end float. Should I be concerned about this and shim it up to that size? Thanks Drummer99

Drummer99 said:

I dropped the bearings out of the cases on 850 Commando There were no shims behind the super blend bearings. I did not measure the crankshaft end play before taking it apart but there was definitely end play there. Now I'm not sure what to do or what the pupose is of the shims. Did they not set the endplay correctly at the factory? Manual says .005 to .015 end float. Should I be concerned about this and shim it up to that size? Thanks Drummer99

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Yes.
You might put a .010 in there to start and have a .005 on hand to adjusts either way. It may take more but not likely.
Yes, this requires you to put in and take out the outer again as needed.
Alway heat the casting when putting in or taking out to save on wear and tear to the casting. Chilling the outer will help it to drop right in.
I find a heat gun works just fine for this procedure. I am not a pro but I have done it a couple times.

would that be .010 on each side or one side at a time How did you measure the end play? Thanks Drummer99

That would be a total of .010 to .015.

None of them were shimmed from the factory.

You can shim it if you would like but for normal use it isn't needed unless the end play get's over about .030. Jim

I've wondered if any shims needed as seems drive train and rod connections self center, but don't know for sure, as have either TS ball bearings twice or just left plain rollers in to shift for themselves. I am not saying not better to stabilize centered but maybe its not very important but to feel good as tedious mechanic. Am I off my rocker on this or thinking right?

Drummer99 said:

would that be .010 on each side or one side at a time How did you measure the end play? Thanks Drummer99

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Generally the drive side cause it's easier to take on and off. You could put a .005 in the timing side then adjust it in from the drive side.

But as Jim says, you maybe just fine.

Put the cases together with a couple fasteners and with a dial indicator at the and of the crank, tap it to one side with a wood block, zero the indicator, then move it to stop in the other direction. Do it a half dozen times to validate your reading.

Must confess that I can't see the point in shimming a few thou with almost paper thin shims that, if anywhere, should be behind the outer race. I much prefer things to have a bit of space to move, who knows how much things expand bend and like to move a little?

What Jim says above................... plus seeing how you did not measure the end play before dismantle, if you started with 0.005" to 0.010" thrust clearance and blindly add a 0.010" bearing shim you would be at 0.000" to -0.005" clearance. You need to confirm what your clearance is if you add shim.

Unless the bearings are destroyed, clapped out or severly worn or damaged when you "felt" the thrust clearance, installing new bearings will give you about the same thrust clearance you had with the old bearings. This is due to the reltively tight manufacturing dimensional specification of the bearing envelope.

I've commented on this subject before, most of the exploded diagrams in the parts books are wrong in that the shims are shown behind the outer race, however if you order these shims using the given part numbers from a Norton supplier it is obvious that they are designed to be placed against the crank cheek on the inside of the shaft holding the inner race. I personally think there is some risk of damage to the soft alloy cases and perhaps overheating of the outer race by removing the outer races numerous times. What I do is to keep an old inner race in my special tool collection where I have ground the inner diameter such that it just slips nocely over the crank shaft, I use this to get the end float where I want it and only then put the new inner onto the shaft. Bearings are manufactured to a much higher tolerance than the clearances that we are working to so effectively there is no difference between the fit of the newly purchased inner and the old ground down outer that I use. To get an old inner race off a crank shaft, I find that a bit of heat from a gas torch carefully played on the bearing from about 6 inches away greatly assists the removal of the inner and most times it simply slides off with a couple of screwdrives as levers under the lip.

I understand opinions will vary but based on my experience and what others have told me, I will not place the shim on the main journal behind the inner race but rather in the cases outboard of the outer race.

As for heating the inner race with a torch, be extremely careful with the direct application of heat on the bearing surface. It is relatively easy to alter the characteristics of the roller surface and end up with premature bearing failure.

Dances with shrapnel, the standard shims as ordered out of a Norton parts book are not the right size to fit behind the outer races and there is as much chance of overheating the outer race and other damage to the cases by contiinually putting it in and out of the cases. You are correct that you can lose the case hardening with indiscriminate heat on the inner, but using my method you only have to take the old one off once and discard it and the new inner will only be put in place Cold once the end float shim requirement has been established, the races hopefully never have to come off again until the bearings are replaced.

Why do people shim Commando cranks but not the cam shaft? Seriously Really want to understand if I'm missing some reason to do so, beyond just feeling like ya did something thoughtful useful. My teachers used to say there were no stupid questions, til I raised my hand. I've only seen attempt to limit slip ~.0015" slip with some centering concern but this assumes you've answered these frist...
1. is something pulling crank to one side to cause rods are binding crank and piston. If so which side? Does in slap both ways?
2. are cases bores machined-matched to go by them to center rods on journals?
3. Is centering evening rods position on journals a conern?
4. are rods centered to piston in bores and crank journals when crank centered in case slip amont?
5. what happens to those who just slap em together, so could even tell if they didn't pay any attention to above? What is the fear and shame damage factor?
6. why not spring washers like the factory rocker spindles on valves?
7. What is wrong with shim to no slip when cold so heat creates some or would expansion tighten up more?
Dave M, thanks for pointing out another flaw in factory manual to be aware of.

The problem with installing the shim on the crank is that often times it comes out in pieces. Not a big problem on the timing side as the oil pump drive gear keeps pressure on the bearing to pinch the shim but on the drive side the bearing will back slightly away from the shim and the shim will come out and do damage. I have seen it happen several times.

As long as you heat the cases to the proper temperature before removing the outer race then there is no damage done as there is no interference. The bearing simply drops in and out. Jim

comnoz said:

The problem with installing the shim on the crank is that often times it comes out in pieces. Not a big problem on the timing side as the oil pump drive gear keeps pressure on the bearing to pinch the shim but on the drive side the bearing will back slightly away from the shim and the shim will come out and do damage. I have seen it happen several times.

As long as you heat the cases to the proper temperature before removing the outer race then there is no damage done as there is no interference. The bearing simply drops in and out. Jim

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+1

Along with the inner shim coming out, I have seen at least three instances where the shim was either installed or creeped off center and was pinched between the filet of the main journal and the filet of the inner race. I don't think that the non concentric condition is a good thing there. If it was installed that way it could give a false indication of what the end float will actually end up being after cycled a few times.

No doubt you need to get the correct shims if the standard shims as ordered out of a Norton parts book are incorrect. Correct shims can be sourced through McMaster Carr or some other bearing catalog or bearing supply house.

Yes, if one chooses to comit to shims on the main journal rather than in the cases, then a used and slightly oversized id inner race is a slick way to check and set things up. One could easily take the inner part of the bearing being replaced and polish out the id a bit to forma a nice slip fit. The surface of the bearings are harder than a teenager on his first date so machining out the id is not an easy proposition.

hobot said:

7. What is wrong with shim to no slip when cold so heat creates some or would expansion tighten up more?

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You want some thrust clearance to allow the bearings to accomodate their design allowable misalignment. WIth zero clearance the barrels are hard against the thrust surfaces and when you get misalignment at speed (or due to Norton manufacturing tolerances), this condition cannot be good.

Furthermore, if you set the zero thrust in a warmer day (summer), the crankshaft bearings will be in a bind in colder (winter) temperatures; at least on start up due to difference in coefficients of thermal expansion between the crankshaft and cases.

There could also be an instance where the bike is warmed/hot, you shut it down and the cases cool. I am pretty sure the cases will cool much more rapidly than the crankshaft. Refering to the fact that the crank and cases have different coefficients of thermal expansion, the hotter crank will bind with the cooler cases.

Bottom line is that end float is necessary for the Norton twin crankshafts. As for the cam endfloat, see the OP; best to start a new thread on cam end float.

hobot said:

Why do people shim Commando cranks but not the cam shaft?

Dave M, thanks for pointing out another flaw in factory manual to be aware of.

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I shimmed the cam when using an ex-works Lucas Rita ignition set up, this was required to ensure the reluctor never hit the pick up! The ideal shims fort he job turned out to be John Deere tractor steering box shims!

Also turns out that Norton crankshaft shims are something else in my parts box I am never going to use!

Ok Dances I see your points on allowing some freedom even at coldest contractual. Still don't see the need of crank shimming yet, though it does appear to make sense even to me, but not sure why is all.

Steve A. you have alerted me on cam end positioning that may of been a reason me and my buddy could not get a Pazion to fire consistently enough to run yet everything tested perfect.

hobot, it's really a simple formula, too much end play and you should shim.

The manufacture recommended a range that you should be within.

That is it.

I'm not as smart as you in this area so though I now understand the minimal amount of shift to leave in play for safety, I do not yet understand why not leave even more slack or no shims [ie: seat inner race up to cheek and let that drift the outer race centered on roller in case bore, so what if a gap behind it] if the crank is not being pulled out of rod thrust alignment. I a hot head now on 'over' heating cases so no hang up drop ins no more no thankyou. Comnoz mentioned the oil pump drive pulling crank to the TS so maybe just shim there, which implies the crank is rubbing side loads on roller bearings not meant to take that much.

In other words what are we centering crank to, just the cases visually or the piston bores? Would there be any benifit to assemble and push pistons to BDC to center rods on journals then figure out which side gets what shims to help keep it there when engine enters its elastic zone of operation.

hobot said:

Ok Dances I see your points on allowing some freedom even at coldest contractual. Still don't see the need of crank shimming yet, though it does appear to make sense even to me, but not sure why is all.

Steve A. you have alerted me on cam end positioning that may of been a reason me and my buddy could not get a Pazion to fire consistently enough to run yet everything tested perfect.

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I had excessive endplay with my cam that effected the usability of the power arc, but never the Surefire.

Added the second thrust washer on the timing side brought the endplay within specs.