Author Topic: Crankshaft shims a10 preunit  (Read 6087 times)

Offline Caretaker

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Crankshaft shims a10 preunit
« on: 10.03. 2006 16:35 »
Hi, have had a recurring problem with the LH crankshaft shims, doesn't seem to last long at all, and suppose the wear accelerates as the clearance increases. Anyone with some suggestions for the cause, or are some shims better than others (quality of steel)? A good source to buy a set of the best available shims?

Thanks
Erling
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Offline bsa-bill

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Re: Crankshaft shims a10 preunit
« Reply #1 on: 19.03. 2006 18:05 »
You are placing the shims between the bearing and the crank web I presume
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline Caretaker

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Re: Crankshaft shims a10 preunit
« Reply #2 on: 19.03. 2006 18:52 »
Hello, thanks for your post. Yes, placed where they should be, & correct clearance. Then They get worn down much too quickly (I find the rest of them sticking on my magnetic sump plug  >:( ) & clearance & noise increases. Apart from this everything looks & works fine with the engine. Since it's lots of work to dismantle the engine to get new shims in, I'd like some hints about how to make them last longer.

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Erling
"Sometimes I say things that are so highly intelligent that I do not understand a word of it"

Offline bsa-bill

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Re: Crankshaft shims a10 preunit
« Reply #3 on: 22.03. 2006 19:59 »
Well the thing is if they are between the crank web and the bearing inner they should turn with the crank and the bearing, that is to say in relation to the crank and the bearing inner race they should be staionary, so should not be subject to wear.
Crank end float should be 3 thou 0.003 maximum, between 0.001 and 0.002 should be aimed for. bearing inner should be a tight fit on the crank ( should not be able to turn it on the crank )
I can't think why the shims should break up
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline Caretaker

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Re: Crankshaft shims a10 preunit
« Reply #4 on: 03.04. 2006 13:57 »
Thanks for the post, so maybe my problem is actually the bearing, the inner race somehow getting stuck sometimes. Looks ok, but with load things can happen. So a new bearing & new shims together next time I split the engine.

Thanks
Erling
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Yvon C.

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Re: Crankshaft shims a10 preunit
« Reply #5 on: 14.04. 2006 03:45 »
If your bearing is loose and you suspect it turning on the crank, one way of correcting is using a small center punch and peening (I think is the correct term?) the crank the with of the bearing and all around the crank the peening should be done about every 1/8" that will make the crank a little bigger.Good luck. Excuse my english.

Offline dpaddock

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Re: Crankshaft shims a10 preunit
« Reply #6 on: 07.10. 2006 19:51 »
No offense, Yvon, but it's much better to copper plate or flame spray the shaft. Better concentricity and load area are the chief advantages. Keep in mind, this is the drive side which carries not only the chain force reaction but also half of the engine dynamics.

And, as Bill says, keep the clearance to minimum.

D/
David
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beesageesa

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Re: Crankshaft shims a10 preunit
« Reply #7 on: 26.05. 2007 15:33 »
Best bet by far if the bearing inner race is 'creeping' on the mainshaft and is not 'really, really loose'-as in rattling about-is our old friend Loctite. When fitting the inner bearing race, also make sure that it is hard up against the crank web as any clearance will allow the shims to move and thus break up. Loctite, I am informed, should have no problems coping with a .001''-.0015'' clearance between race and mainshaft, which is actually quite a lot. If you have a lot more clearance than that, hard-chroming or metal spraying is the answer but could be expensive.  Hope this helps.

Beesageesa

Offline dpaddock

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Re: Crankshaft shims a10 preunit
« Reply #8 on: 26.05. 2007 16:23 »
Erling:
Recall that what holds all this together is the cush drive assembly. If it's worn or loose, the drive side shaft will be pulled and pushed against these shims, thus bashing them to destruction (in the worst case). The usual wear item is the spring which relaxes over time and fails to hold the shaft forcefully against the bearing. The free length of the spring is 1.675 inches and the spring should be replaced if it's 1.650 inch or shorter. Its p/n is 67-1136.
David
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Online RichardL

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Re: Crankshaft shims a10 preunit
« Reply #9 on: 11.03. 2008 11:44 »
Gents,

I could use some advice. I just did my first pass (since 2006) at shimming the crankshaft. My shimless measurements indicated I needed 0.038" to allow 0.001" of clearance. On measuring the shims that I took out, what a surprise, they totalled 0.038". I decided to put togther a stack of 0.037" to allow a for measurement error. Using mostly new shims, I put the thin ones in the middle of the sandwich. On checking the fit, the new play seems to be less than the accuracy of my measurement method. Specifically, I sit the crankcase primary side on blocks, tap down the crank and measure with digital caliper as a depth gauge down to the face of the timing-side journal. Then, stand the package on the primary end of the crank, tap down the crankcase and measure again. [Once again, I envy anyone born with three arms (a risky joke, in case any of you have loved ones with three arms, if so, sorry)]. With apparently immeasuable play, I am assuming less the 0.001", the crank turns just a bit snugly. It can be turned via the primary shaft with hard-working fingers; the whole fist is not necessary. It doesn't free-wheel, but neither does it stop immediately when given a firm turn via the flywheel.  So, my question is, do I leave it like this, assuming a smear of gasket sealer on the crankcase mating surface and some running time will make it fully loose? Would there be any question of the timing-side bush face getting enough lubrication?

Thanks for your advice and opinions. As much as I find using my home-brew bearing puller a novelty (you might remember it from the little quiz), I would be happy if I got it right the first time.

Richard
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.

Online groily

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Re: Crankshaft shims a10 preunit
« Reply #10 on: 11.03. 2008 17:59 »
Re bearing race to crank, agree 100% about the virtues of loctite - easily up to the task, provided we're really talking a thou or so. While one can peen an OUTER ball- or roller- race into a crankcase relatively well - some engines were built like that for extra security - peening the crank to inner race is not such a great plan in my opinion. Apart from anything else, when next replacing the bearing, the thing will need a good clean up, and could be a looser fit still.

Re shims and measuring, have to say that's one thing I haven't had to do for a bit. But, a dial test indicator is a better beast than a slide gauge (and not too pricey these days) because you can set it up dead square and dead still on one of those (also cheap) magnetic stands, and push/pull the crank from side to side to check the end-float easily, if the engine is bolted to a stand, the bench, or the garage floor. Not that a digital caliper/depth gauge can't do it, it can, it's just that the merest angle or shiver in the operator's hands will give a false reading. Personally, if I had between 0 and 1 thou with things turning freely enough as you describe Richard, I'd be happy with that. After the thing's run a bit, warmed up, cooled down, crankcase joint and nuts and bolts have settled, etc etc, can't be far out. To my mind, the key thing is that everything is pretty free to turn and there's no appreciable float.

Can I just ask, re dpaddock's point on the shock absorber arrangement .  .  .  Given that end-float isn't set with the shock absorber and sprocket in place, there should be no difference in end float with it off or on. Looking at the thing, and given that the sprocket doesn't bear against the crankcase (disaster if it did), I am having trouble seeing why it could cause such dire trouble inside. The spring and its nut don't pull the crank anywhere do they? They just go up tight to the sprocket, outboard and independent of all arrangements on the inside. The crank will move sideways as much and as easily with the s/ab assembly done up to a million ft pds as it will when it isn't there . . . .
Now, unchecked lateral movement of the c/shaft sprocket on its spline would be very bad news, I agree - for just about everything from engine to gearbox via clutch. But to have free movement - even with a worn spring - the s/abs nut would have to have undone itself quite a lot and anyone in earshot as the nut ground out the primary chaincase when it went round would be looking for another planet to live on. Either I am missing something vital here because my brain has faded, or the crankshaft shock absorber spring has no direct effect on the main bearing and its shims or the end-float. Put me out of my misery please someone! Groily

Bill

Online RichardL

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Re: Crankshaft shims a10 preunit
« Reply #11 on: 11.03. 2008 18:28 »
Groily,

Ah! The loctite. I forgot about that. Maybe that is reason enough to remove the bearing again and lose .001" from my shim stack. I'll think about it. 

You're right about the digital caliper. It seems that no matter how many measurements I take I'm always second guessing it. I really should be a good little engineer and record about twenty measurements to find the average.

Regarding the cush nut, it seems that dpaddock is on the same track as the folks at SRM, who explained it to me a while back (when I was diagnosing my engine problem). Here is what they said:

The metal [meaning, what I found in the bottom of my crankcase] is more than likely shim material, common problem caused by the non tightening of the cush drive nut in the clutch side, clanking is cush drive assembly loose on the crankspline, and possibly loose crank bearing on the crankshaft.

The cush drive nut is critical, must be 65 foot lbs torque tightened, this holds the cush drive assenbly tight against the oil seal spacer, which in turn holds the crank bearing , which in turn hold the shims against the crankshaft; if this is all loose , crank splines wear badly, crank bearing wears crankshaft so it is loose fit on shaft , and shims break up and fall inside engine. Usually if the split pin has been fitted above the cush drive nut , when nut comes loose, it goes against pin, and you dont know it's loose, happily riding and causing engine damage, best to leave this pin out, so nut touches primary cover and makes a noise , so it is investigated before the serious damage is done. But this is not the casue of the engine noise !


Well, I guess I'll ponder the issue a little longer on the possibility of more confirming opinions. I suppose I have a little time, since my friendly "machinist" also forgot to pack the bearing shells I bought from him. The weather is changing here and LJ's and Kev's photos, while great and inspiring, are also p'ing me off!

Richard




Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.

Online groily

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Re: Crankshaft shims a10 preunit
« Reply #12 on: 11.03. 2008 20:30 »
Well, thanks a lot for that quotation, Richard - guess it must be true. All sources' credentials impeccable. As I said, I'd agree there's a risk if there was in-out movement on the sprocket and it was clacking about on its shaft. I guess the clacking about would transmit unnatural slide-hammer type shocks through - and happens more easily than I thought it could.
Quite how one is to get a torque wrench on what is not a proper nut, however, is another question. I have simply done mine up darn tight and put a split pin in. (Wouldn't feel comfortable without something in there to stop it all unravelling, even though the noise would be a good early warning of trouble I suppose). But how tight is anyone's guess. Did think about making something with a proper hex on it, but feared it might foul the primary case etc and give me the big noise anyway, plus it's quite a big internal thread to have to make, in what is a pretty important application. Re your comments about torque wrenches a few weeks ago, most original owners presumably did them up with a C spanner or a chisel and left it at that . . .

However, re the most excellent loctite, it won't help with shimming - I think the Q there was 'how to hold main bearing inner race firmly on the crankshaft', not 'how to reduce end-float'! I still think your end-float is probably OK, but there be people here who will tell you for sure. Heartened (although sorry too!) to hear that a slide gauge ain't that easy to use for this particular job - because I agree 100%. If you get a 'clock', you'll be amazed how useful it is for all sorts of things - you could even measure with accuracy any imperfections in that there cylinder head face (oops). I bought mine when I got a lathe quite a few years back, and it is just incredible how much it tells me that other things can't. Makes me weep sometimes to find that what I think is perfectly turned or milled is in fact little better than scrap - but that's the difference between properly trained craftsmen and wanabees like me. The other difference is I have all the time in the world to do it again . . . and again . . . while they have a foreman looking over their shoulder, as well as professional pride to contend with. Dogs, walking and hind legs come to mind. Groily
Bill

Offline bsa-bill

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Re: Crankshaft shims a10 preunit
« Reply #13 on: 11.03. 2008 20:43 »
I'm with Groily on the cush drive issue, if everything is as it should be the crank can't move more than the 0.001 or so you set it at, if there is excessive end float then yes it's going to bang in and out.
I would think what you have is fine.
First crank I did was with a calliper and yes I took about twelve readings and took an average, second was recent, I bought a cheap dial gauge and got it first time, this was a second attempt however as the shop made a mistake of some kind and the crank was solid even though though there was plenty end float, don't know what they did wrong as they reckoned they did exactly the same the second time and it was fine, cost me another bearing though, I think they bored it off line first time.

All the best - Bill
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

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Re: Crankshaft shims a10 preunit
« Reply #14 on: 12.03. 2008 17:28 »
Love the nut, Richard, gives me a rough pattern to follow - nice Stilson wrench too -  for the central heating system! Have to admit to having used a massive pair of slip-jaw pliers on my old-style nut - 2 feet long nearly and you can do terrible things with them - also for plumbers I reckon . . .
Bill