Author Topic: Crankshaft shimming  (Read 1849 times)

Offline BSA500

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Crankshaft shimming
« on: 22.05. 2018 12:45 »
Well here go again. Audible clunk when the cranks moved in and out. Cush nut fully kin tight 65ftlb. no other work done so timing bush ok no up and down play. The reason why I don't know but there will be careful checks. Oh no shim break up either. My question other than why  *pull hair out*. Can you reduce the clearance to around zero without issues. There is plenty of side movement on the pistons/conrods is it necessary to have some allowance??

Offline duTch

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Re: Crankshaft shimming
« Reply #1 on: 22.05. 2018 13:18 »

 Have you measured it? It can produce quite a clunk with very little movement (less movement than you'd expeect), but I'll let the others talk you through the rest....
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline BSA500

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Re: Crankshaft shimming
« Reply #2 on: 22.05. 2018 13:49 »
I have to much experience with this issue(don't ask).This movement is too much and the vibration  is horrible. I can also try to sort out an annoying tapping/clattering.

Online berger

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Re: Crankshaft shimming
« Reply #3 on: 22.05. 2018 14:35 »
I flooded mine on sunday and when it did the odd fire I heard this horrible clunk noise too, its not long ago that I built her up. theres nothing on the sump plate regards shims like there was a few years ago but I do intend to investigate end float when changing the gearbox in the near future, I do know the metal on metal sound is a horror to hear you have my best wishes on finding a cure or reason for this and I hope I get an answer regarding my CLUNK , ime hopeing its not end float because a got that to about 1 and half thou.

Online muskrat

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Re: Crankshaft shimming
« Reply #4 on: 22.05. 2018 21:20 »
G'day BSA500.
I agree with duTch, measure the endfloat first before pulling it down. If it's under 5 thou" I'd just monitor it.
Was the bearing a tight fit on the crank and the outer a shrink fit in the case? How much shim did you use?
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Offline BSA500

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Re: Crankshaft shimming
« Reply #5 on: 22.05. 2018 22:01 »
The bearing is fitted using loctite 641 and I have bent bearings in The past trying to shift them. The trick is to dissolve the loctite using acetone.
Cannot remember what shim pack I used but the noise vibration is horrible so it's coming  down I shall measure the float before.

Offline BSA500

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Re: Crankshaft shimming
« Reply #6 on: 24.05. 2018 11:13 »
Had an idea on How to make the shimming quicker and hopefully a little more accurate.
Take the crank out and clamp into a vice carefully. Remove shims bearing etc. Slide the bearing on- not all the way and then assemble the shock absorbed sleeve sprocket and tighten fully. Measure the gap shim and put back into the crankcase and a final check with a dial gauge. Any pit falls and has everyone else been doing this for years

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Re: Crankshaft shimming
« Reply #7 on: 24.05. 2018 20:30 »
NNNOOOOOO.
It all depends on where the outer race sits in the case and any wear on the thrust face of the timing side bush.
The end float of the crank is between the bush on one side and the bearing rollers against the outer race lip on the other side.
It's a PITA job but it must be done the way it's always been done.
Nice try though.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Offline Peter Gee

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Re: Crankshaft shimming
« Reply #8 on: 24.05. 2018 20:41 »
Dear Muskrat, since I will soon be doing this job, what exactly in detail is the PITA method?

I do have the original crankshaft shim pack out of my unopened A7SS ( until I opened it) and a new one. Shall I just assemble up a new shim pack to the old dimensions?

I will also be using the same Steel backed TS bush that also came out of the bike, but with a new SAE220 insert.

A

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Re: Crankshaft shimming
« Reply #9 on: 24.05. 2018 21:10 »
G'day Peter.
1st if the T/S bush has been removed from the case may as well drop it in the bin. It wont go back in EXACTLY as it was and will need to be line bored again making it too big for the crank.
Once the bush is in and line bored/reamed to suit the crank. Put the drive side bearing outer in the case (heat the case and freeze the race) and the inner on the crank (I soak mine in boiling water for a few minutes and it drops on all the way). Now assemble the cases together (torque all the bolts) and fit all the cush components and torque the cush nut (65ft/lb). Now measure the end float with a dial gauge. This measurement less 1 thou" is the shim size needed (may need more than one shim but don't use more than three, get thicker ones). Now it all comes apart again to install the shims behind the inner race. Removing the inner race can be difficult, I first pour boiling water over it. If that don't work I pop the rollers out of the cage and use a bearing spliter type puller to remove it.
Once the shims are in place and inner race back on assemble again to recheck the end float. Sometimes it may need to be done more than once.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Muskys Plunger A7

Offline Peter Gee

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Re: Crankshaft shimming
« Reply #10 on: 25.05. 2018 06:31 »
Dear Muskrat,

No problem on the first matter. I am using my OEM TS steel cage to have turned and pegged new insert made for it- it won't be lead bronze ( cant get it) by lead phosphor SAE660 and of course it will be line reamed. I have enough materiel in SAE 600 to actually to turn a whole one piece bush if I so decide..

For your second advice I do have a dial gauge and I have a wide selection of shims and shim stock too. Your description has been very helpful as to the exact figure I need and some tips to manage it. Luckily my inner DS bearing is not too stubborn and it toois original and in VGC,  will not replace it...my bike will not be doing long mileages, mostly weekend  small runs.. Cheers

Online Greybeard

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Re: Crankshaft shimming
« Reply #11 on: 25.05. 2018 09:23 »
Musky, please explain why the engine shock absorber needs to be fitted. I did not fit mine when I reassembled my engine last time.

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Re: Crankshaft shimming
« Reply #12 on: 25.05. 2018 10:27 »
Your right GB, the spring and sprocket can be left off, as long as it's all locked up snizentite.  ::hh::
Now get back out in the shed and clean all those parts and polish the rods. You want it all ready for when parts arrive  *lol*
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

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Re: Crankshaft shimming
« Reply #13 on: 25.05. 2018 11:51 »
OK you've still left me wondering. Are you saying the shock absorber nut needs to be done up?

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Re: Crankshaft shimming
« Reply #14 on: 25.05. 2018 12:14 »
Yes, eliminates the possibility of the inner race moving on the shaft. I know if it's tight on the shaft it shouldn't but!
Just to be on the safe side I like to have it as though the motor is running.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7