Author Topic: Crankshaft side play/shims etc  (Read 4938 times)

Online RichardL

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Re: Crankshaft side play/shims etc
« Reply #120 on: 24.08. 2018 21:19 »
Almost shy to ask a shim question here, having read so much on it, written so much on it, and been given so much good advice. Nonetheless, I don't recall this question being asked by me or anyone else, and if it has, there is too much info to sift through to find it. 

Question is: Should we target an allowance for the minimum amount of side play before installing shims? I want to tell my machinist to dress the face of the new T.S. bushing so the crank is not locked up when the cases are assembled. I don't think it would be good if the play (without shims) was, say, 0.004".  That would mean the shim (or shim stack) might be just 2-3 thou thick. Arguments for specially machined thick shims seem to support the notion that such a thin shim, by itself, is a recipe for shim destruction. ("Well, Richard, if you get your bearing on right, tight to the web and with the shim sandwiched between and (maybe) Loctited, the shim should be fine, you dummy."  Then I say, "Well, yes it should, so why bother with custom-made thick shims?")

Going back to my original question in the recent rebirth of this topic. 

I've removed the old two-piece bushing to find that its flange is 0.011" thicker than my new solid phosphor bronze bushing. So, asking if the machinist can skim the bush to create minimum side play seems a moot point.

Richard L.

Any thoughts?

Richard L.
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 muskrat

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Re: Crankshaft side play/shims etc
« Reply #121 on: 24.08. 2018 21:43 »
G'day Richard.
That's a good example of why shimming needs to be done. With after market parts coming from all parts of the globe there's bound to be differences.
If the old one was thicker in the thrust flange tan std I wonder what the PO did to the cases or crank to make it fit (grind thrust face of crank, counter bore the case etc).
Looks like it's back to shims for you.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Online RichardL

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Re: Crankshaft side play/shims etc
« Reply #122 on: 24.08. 2018 22:43 »
Well, I'd planned on shimming anyway. Thrust face of crank and landing at case look unmolested

Richard L.
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.

Offline ianbsa

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Re: Crankshaft side play/shims etc
« Reply #123 on: 01.06. 2020 11:40 »
What a great forum, and well like a kid in a candy store etc...so much amazing stuff to digest.

I know this thread is old but thgt it would be interesting to hear thghts on the shim issue.  I hate those darn shims...When they break up that glass hard stuff will destroy an engine in a second.

I shimmed with said shims to get the end float, got it all measured up, removed them and then turned up a single solid shim to size from some tough tool steel which I played with the heat treatment then loctited in place. Just seems less likely to break up so to speak.
Time will tell I guess.

Offline bikerboy

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Re: Crankshaft side play/shims etc
« Reply #124 on: 02.06. 2020 00:32 »
Nothing to do with shims but a story from when I was young and a lot fitter than I am now. A few of us travelled up to the lake district many moons ago and one of the lads was on an A10 plunger which started knocking like crazy. We took the engine out in a car park and we took the head barrels and rocker box off in one piece. Nothing unusual the left hand big end had gone. After getting a new set of shells we bolted it back together we debated whether or not we would need to rest the tappets. Common sense won out (for a change) and we took the rocker box covers off and only one of the tappets needed adjusting and that was only by a few thou. The bike made it back to London and ran around for a few months before it started knocking again and he could then get the crank ground etc. etc.

It always strikes me as quite bizarre that nowadays with a hell of a lot more money and a hell of a lot more mechanical knowledge that our bikes need so much cossetting and care compared to those days when with 3 spanners, a screwdriver and a lot of luck they used to take a dreadful thrashing and still survive. I still have the A10 I started with 47 years ago and I distinctly remember throwing the crank shims away the first time I stripped it because I did not think they were that important.  We just never had the money or the knowledge to do anything else but bodge them up but I swear my bikes give me more trouble nowadays and I do just about everything right  *sad2*



Offline ianbsa

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Re: Crankshaft side play/shims etc
« Reply #125 on: 19.06. 2020 10:11 »
Nothing to do with shims but a story from when I was young and a lot fitter than I am now. A few of us travelled up to the lake district many moons ago and one of the lads was on an A10 plunger which started knocking like crazy. We took the engine out in a car park and we took the head barrels and rocker box off in one piece. Nothing unusual the left hand big end had gone. After getting a new set of shells we bolted it back together we debated whether or not we would need to rest the tappets. Common sense won out (for a change) and we took the rocker box covers off and only one of the tappets needed adjusting and that was only by a few thou. The bike made it back to London and ran around for a few months before it started knocking again and he could then get the crank ground etc. etc.

It always strikes me as quite bizarre that nowadays with a hell of a lot more money and a hell of a lot more mechanical knowledge that our bikes need so much cossetting and care compared to those days when with 3 spanners, a screwdriver and a lot of luck they used to take a dreadful thrashing and still survive. I still have the A10 I started with 47 years ago and I distinctly remember throwing the crank shims away the first time I stripped it because I did not think they were that important.  We just never had the money or the knowledge to do anything else but bodge them up but I swear my bikes give me more trouble nowadays and I do just about everything right  *sad2*

Great story, similiar to my dads AJ which someone fixed roadside.
I think the problem is that we are so used to "silent" japanese stuff that these old bikes now sound like they are literally falling apart so we keep fettling them.

Back in the day at least everything was less worn so to speak. Some parts of the engines today cant be fixed and are almost hanging on for dear life. Take the cam follower tubes for instance..there is almost no-way they can be fixed if worn and new followers ain't gonna fix it.  Im sure the clatter you hear from the A series bikes comes from from those tubes which need to be a very tight sliding fit...Same with the rocker gear its all worn now so contributes to the mayhem and cannot be repaired.  Just my 0.2$