crankshaft bearing shims

reassembling MK3 crankcases and unsure if shimming needed or not. Workshop manual for MK3 makes no reference to measuring crank end play or shims. Replacement parts catalog list shims as required.
Does the Mk3 come from the factory without shims (only 10K on this engine) or if I need to measure and install shims, if so :roll: where can I find instructions to do so?

Keith Clark said:

reassembling MK3 crankcases and unsure if shimming needed or not. Workshop manual for MK3 makes no reference to measuring crank end play or shims.

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Mk3 Factory manual, Tech. Data section:

Crankshaft.....

Permissible end float: 0.010" /0.024" (0.254 mm/0.610mm)

Keith Clark said:

if I need to measure and install shims, if so :roll: where can I find instructions to do so?

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http://www.oldbritts.com/11_067569.html another source of instructions.

Dave
69S

If someone can enlighten me on how to measure endplay/float, my problem will be solved.

Keith Clark said:

If someone can enlighten me on how to measure endplay/float, my problem will be solved.

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The usual method would be to bolt up the crankcase assembly complete with crank and bearings, and then measure the amount of end float with a dial gauge.

If shimming is required, then a bearing race or perhaps both races (either inner or outer) will have to be removed in order to fit the necessary shim/s.

The whole thing is then assembled again and the play re-checked.

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Thanks, was thinking measurement was taken inside of crankcase, wasn't thinking (outside the box) will have no problem now.

Keith
I'm building my engine at present and I did this:
1. Bolted the empty cases together and precisely measured the distance between the bearing mounting faces. I did this with a thin rod which I gradually shortened until it fitted snugly between the faces. I could then measure the rod with a vernier caliper.
2. Set the bare crankshaft up on a surface plate and placed an engineers square against each bearing face. Then measured between the squares with the vernier.

Then you can measure the bearings to calculate how much shimming is needed. If it's a fair bit like mine was (.030" end play), you can even out the shims at both ends.

This gets you very close, but its best to do a test assembly for final adjustment.

A tip that was suggested by daveM on "Main Bearing Specs" : Use an old bearing, if you have one, that has been ground to make it slide easily into place (internally for the inner race, externally for the outer race), on one end during test assembly. This saves you from having to heat the case to remove the bearing to make adjustments. If you're shimming on the crankshaft its even more crucial as the only way I have been able to remove the inner race is by grinding it off.
I didn't have the luxury of an old bearing so I had to re-heat the case to make final adjustment with an Old Britts crankcase shim.

Cheers
Martin

The Crank in my 850 is running 020" end float to acommadate the crank flex and other missalignments and i flog this to 7500rmp each gear and it has stock cases no worrys after 7 years racing. To acheive more clearence i used loctite 515 and nipped the cases up softly and waited 10-15 minutes for the 515 to off a bit then torqe the bolt and recheck may take 2 or so goes but this work very well. I have used this method for alot of year rebulid indusrial gearboxes to exact spec.

I have disassembled the 1971 crankase carters and I removed the old original bearings but I could not find on both sides the shims.
Now that i will mount  the two FAG superblend should I do to see if measurement range thickness?
Thank you
Piero

If your 1971 had the original ball bearing on the distribution side, the crankshaft was nos able to move sideway . It could be the reason why you have no shims.

Replacing them by 2 rollers bearings (superblends) is a good idea but you need to check the end float . Anyway lots of motors are running with more end float than factory requirement without critical issue, anyway less float is a no-go.

JRD said:

anyway less float is a no-go.

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Hi and thank you.
Please, what does it means "no-go"?
Ciao.
Piero

it means it's absolutely mandatory to have some end float . You must not go with less than required.

By the way I'm French , if you're comfortable with French here is a very valuable site with a forum http://www.motos-anglaises.com/, with some people having a deep knowledge on Commando.

If I may add, going with a superblend in the drive side and a ball bearing in the timing side is still a viable option and should or can be concidered. Many builder still do this. The important thing is making sure you use a superblend in the drive side.

There is a two sided testing device in manufacturing called a "go,no go" guage. These testing devices are for checking tolerances the various thing. If one side fits, it's a "go" or exceptable. It the other side fits or does not fit depending on the type of test, then it is a "no go", not exceptable. In this case, no end float with two superblend bearings in a "no go", not exceptable.
I hope this helps.

Thaks a lot.
If i have understood well, if i fit the superblend only on the drive side (left) and using the standard on the timing side, i dont need to fit any shim:
Andover dont supply the shim to fit in back of the superblends but only less large shims to fit on the crankcase: it works well or is better to fit the large OldBritt supplied?.
if i fit the two superblend i can fit the shim on the two side or only one, and what is the tollerance minimum and max i can have a "go"?.
Hopefully your help.
Regards.
Ciao.
Piero

Go here,
http://www.oldbritts.com/11_067569.html

pierodn said:

Thaks a lot.
If i have understood well, if i fit the superblend only on the drive side (left) and using the standard on the timing side, i dont need to fit any shim:
Andover dont supply the shim to fit in back of the superblends but only less large shims to fit on the crankcase: it works well or is better to fit the large OldBritt supplied?.
if i fit the two superblend i can fit the shim on the two side or only one, and what is the tollerance minimum and max i can have a "go"?.
Hopefully your help.
Regards.
Ciao.
Piero

Click to expand...

pvisseriii said:

If I may add, going with a superblend in the drive side and a ball bearing in the timing side is still a viable option and should or can be concidered. Many builder still do this. The important thing is making sure you use a superblend in the drive side.

Click to expand...

Hi Sir,
why if i use a ball bearing i do not need to fit the shims, what is the difference?

Andover supllyed the CRANKSHAFT SHIM.003" NMT 2196A Part Number 067569 but in the web page i can see only one to fit only on the timing side, not on the drive side: altough the shim is back of the bearing fit on the halve case not on the inner race as OldBritt says.

Well, if i use two superblend i must fit two shim or only one?

Thanks a lot.
Ciao.
Piero

balls in a ball bearing can not move side away : this provide a positive location , when rollers can move.

If you have too much end float put as many as require to achieve the right end float, could be none. If you have to mount 2 put one on each side .
the shims sold by Andover are to mounted between the case and roller race.

I think Andover only sells the shims that go under the inner race. Old Britts sells both types. I'm not sure the large shims are available in EU because I sold my unused ones to someone in France a long time ago.

Dave

Well i mean what you told me.
Do you think the isolastic shims are the same like crankshaft shim?.
In any case, what should be the total tolerance of end play?
Thanks.
Ciao.
Piero

Piero,
Please read the whole thread : permissible end float was already given by LAB.
You need to have a workshop manual all needed information to build a Commando are in it. ( you find many links to download one from the web)