No shims behind Super Blend Bearings
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Yep cam drive sucks cam to RH so don't need thrust washer on DS to run right. Crankshaft is pulled to TS by oil pump drive JIm said, which I'd tired to put out of mind after Peel's over rev event. Primary chain/belt would also tend to hold crank in one location under load but don't know it this conflicts with the oil drive pull or adds shove to TS. I of course have to stay in constant reviewing and updating faster than forgetting what I've been though. May we all end up with a fully fettered Commando before we go.
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hobot said:
No, I did not say the oil pump pulls the crank to one side. [someone else did]
Any slight pull the oil pump is going to place on the crank is going to be offset by the pressure feed on the timing side that is trying to push the crank to the drive side.
I have watched the crank motion from side to side. It drifts around wherever it wants to. Jim
rvich
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I have done the crank shim procedure exactly once but it took a few tries to get it right. I am not as tricky as Dave M and my hat is off to him for his process. I suppose if I keep at this long enough I will improve my methods. I certainly hope so, seeing as that is what the journey is partly about. (Really, for me it isn't ALL about going fast, looking cool and drinking beer. Those are just unforeseen benefits).
I heated my cases in the oven until the bearings would drop out, or back in. After determining that I needed 8-thousanths per side I rounded up my shims. The hardest part for me was that the very thin shims did not like to lay flat in the bottom of the bore. I had to push the bearing against them while it was still free to move and hold it in place long enough for the case to capture it and hold it. Otherwise they tended to act as spring washers and push the bearing race away from the case. I suspect this might happen a lot to unsuspecting wrench-monkeys such as myself.
How many of you guys make your own shims? Do you buy shims that lay flat enough to avoid this when they are stacked? I made mine out .004 brass shim stock and it was a bitch to cut it without leaving a bit of a shape in the shim.
Russ
I heated my cases in the oven until the bearings would drop out, or back in. After determining that I needed 8-thousanths per side I rounded up my shims. The hardest part for me was that the very thin shims did not like to lay flat in the bottom of the bore. I had to push the bearing against them while it was still free to move and hold it in place long enough for the case to capture it and hold it. Otherwise they tended to act as spring washers and push the bearing race away from the case. I suspect this might happen a lot to unsuspecting wrench-monkeys such as myself.
How many of you guys make your own shims? Do you buy shims that lay flat enough to avoid this when they are stacked? I made mine out .004 brass shim stock and it was a bitch to cut it without leaving a bit of a shape in the shim.
Russ
I have dismantled a number of cranks that I know to have been unmolested since leaving the factory, the ones that had shims all had them under the inner races, this and the fact that the standard factory supplied shims will only fit in this application indicates that this was Norton factory practice. This is not to say that there is not another way to achieve the same result. Since the crank floats and the shimming requirements are small it is perfectly acceptable for multiple shims to be on the same race and I agree that the timing side race would be the better choice. I personally have never had to put more than 2 shims on a crank shaft, but I have only done a dozen or so of these motors and I'll accept that others with wider knowledge may well have had a different experience.
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As an example, I did a quick search and find Fastenal has steel round shims for placement in the cases; a 0.005" example is what I looked at. Looking around a bit there are plenty of options for materials, thickness and diameters (ID & OD); search for Arbor Shim. If you know what your end play is, you can calculate exactly what you need and order accordingly to spec.
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dave M said:
I have to say I have never seen a crank with a factory shim on the crank.
Ask Chris Grimmet how he liked the 'factory supplied" shim that was used on the crank when his engine was rebuilt. Or Tom Kullen. I can probably come up with a few more cases of spit crank shims if you want. Jim
I don't know either of these gentlemen Jim, but you yourself stated in this thread that it shouldn't be a problem on the timing side where the oil pump drive gear holds the inner race in position - this is where I place any shims when I do this job. Clearly there must have been more than a few cranks that required shimming from new otherwise I can't imaging why Norton would provide for these shims in the parts book and I have certainly found them on bikes where I can say for sure the cases had never been split prior to my own involvement.
I recall clearly the instances of main bearing failure that led to the introduction of the Superblends but I do not recall a spate of failures resulting from dislodged crank shims, while I don't doubt that you yourself have come across this perhaps it has been some factor such as a loose fit between the inner race and the crank that has caused this, or perhaps even too tight a fit not allowing the race to seat fully home on the shaft and thus leaving the shim loose. All of the rebuilds I have done have required considerable pressure to get the bearings seated fully on the crank.
I'm sure we will each carry on sticking to our own method, hopefully with good results for both.
I recall clearly the instances of main bearing failure that led to the introduction of the Superblends but I do not recall a spate of failures resulting from dislodged crank shims, while I don't doubt that you yourself have come across this perhaps it has been some factor such as a loose fit between the inner race and the crank that has caused this, or perhaps even too tight a fit not allowing the race to seat fully home on the shaft and thus leaving the shim loose. All of the rebuilds I have done have required considerable pressure to get the bearings seated fully on the crank.
I'm sure we will each carry on sticking to our own method, hopefully with good results for both.
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dave M said:
I believe you when you say you have found some with shims, but the only ones I have seen had been worked on before. During the period of a year or two it was pretty common for the bike to have the main bearings upgraded before or shortly after they were sold. Shimming them was common at that time. I know Brian Slark told me once that he was not aware of any shims being installed at the factory but that doesn't mean they don't exist.
I would agree, a shim under the timing side bearing was probably safe. As long as it can't get loose and start shaking -it will last.
Chris Grimmet is the president of the NOC. He had his engine rebuilt in GB. Not long after that he lost a shim from the crank which did considerable damage. I didn't ask which side it was on. He sent his cases to me for work during the re-rebuild.
Tom Kullen is the pres. of the Utah British bike club. He had pretty much the same scenario. These were the last two I was involved with. Jim
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Chris Grimmet is a past Chairman of the NOC and is now responsible for NOC forum moderation, including the recent excessive moderation of the forum in relation to criticism of Stuart Garner and his latest money making venture.
Regarding controlling crankshaft end float, I've always fitted them behind the inner races as the ones supplied would not fit anywhere else. Can't see a problem fitted behind timing side inner race especially, as mentioned, because of the positive location supplied by the oil pump worm drive. I was surprised to see them on the Andover Norton website as fitting behind the outer race. No mention of shim location in the Mk3 workshop manual but it does specify min.and max. end float.
P.S Everybody knows 'superblend' bearings don't exist in bearing manufacturers catalogues, don't they?
Regarding controlling crankshaft end float, I've always fitted them behind the inner races as the ones supplied would not fit anywhere else. Can't see a problem fitted behind timing side inner race especially, as mentioned, because of the positive location supplied by the oil pump worm drive. I was surprised to see them on the Andover Norton website as fitting behind the outer race. No mention of shim location in the Mk3 workshop manual but it does specify min.and max. end float.
P.S Everybody knows 'superblend' bearings don't exist in bearing manufacturers catalogues, don't they?
Al-otment,
My understanding from reading a number of sources (I know this sounds like "somebody said") some chap stated that the original Norton exploded diagram was wrong in the illustration of the shim position and that this had never been corrected.
My understanding from reading a number of sources (I know this sounds like "somebody said") some chap stated that the original Norton exploded diagram was wrong in the illustration of the shim position and that this had never been corrected.
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dave M said:
daveM,
Could well be, not all word of mouth stories are incorrect. I get the vast majority of parts from Mick and Angela Hemmings because I'm very happy with their service and quality of parts and assume that's where the shims I've got came from.
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Thinking about this a bit, the round shim installations (inner versus outer) are two completely different applications that are meant to achieve the same result, and that is hold end float to within specified tolerances.
A round shim on the main journal is subjected to spinning on a vertical plane at up to several thousand RPM; ideally it is sandwiched between steel inner race and crank cheek. If the inner race is the slight bit loose, poorly seated or incorrectly seated, the shim will go off center and creep up onto (get pinched at) the filet and beneath the filet of the id of the inner race.
A round shim in the case is loosely sandwiched in a vertical plane between the steel outer bearing race and aluminum cases. No rotation is involved, it just sits there but there is vibration of several tens of Hertz. I have never seen case damage due to shim vibration.
In short, on the crank, round shims are subject to relatively greater dynamics whereas in the cases, less dynamics. In the cases, shims are pretty benign where they cannot go anywhere and do not get deformed or displaced (anywhere of consequence) whereas on the crank they can get out of place (onto the filet), break and cause potentially serious engine damage.
As for Norton apparently opting for the smaller crank mounted shims, maybe the smaller inner shims were cheaper.
A round shim on the main journal is subjected to spinning on a vertical plane at up to several thousand RPM; ideally it is sandwiched between steel inner race and crank cheek. If the inner race is the slight bit loose, poorly seated or incorrectly seated, the shim will go off center and creep up onto (get pinched at) the filet and beneath the filet of the id of the inner race.
A round shim in the case is loosely sandwiched in a vertical plane between the steel outer bearing race and aluminum cases. No rotation is involved, it just sits there but there is vibration of several tens of Hertz. I have never seen case damage due to shim vibration.
In short, on the crank, round shims are subject to relatively greater dynamics whereas in the cases, less dynamics. In the cases, shims are pretty benign where they cannot go anywhere and do not get deformed or displaced (anywhere of consequence) whereas on the crank they can get out of place (onto the filet), break and cause potentially serious engine damage.
As for Norton apparently opting for the smaller crank mounted shims, maybe the smaller inner shims were cheaper.
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Al-otment said:
This does happen. We have reports of shims going AWOL, and I have seen three separate instances of shims offset and pinched tight into the filet; one of these instances was my own billet crank where the shim was confirmed concentric and tight on install but pinched upon dismantle.
A quick look at the pricing of Arbor Shims indicates a smaller shim is about 50% the price of a larger shim.
So yes, if properly installed on the timing side (tight and centered), I also would expect the shims to stay in place on the timing side. I cannot recall where the shims that I observed being pinched came from. Maybe Jim can chime in here to see if he recalls which side the AWOL shims came out of.
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