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A-65 excessive end float
#794349 12/30/19 5:16 pm
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Nick H Offline OP
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I am assembling a 1966 engine and working carefully to get the all important bottom end correct.
I've had the crank dynamic balanced at one shop and the timing side bush line bored at another. I have a new SKF roller bearing on the drive side.
Now I'm setting up the end float on the crank with a set of shims from Master-McCarr.
I've now got a thou or two end float but with .085" of (3)shims in my cold garage.
I am torquing the alternator side and as i worked up to this shim set was noticing that sometimes the float would increase as the torque was added.
The crank turns smoothly.

Besides this being so much more shim than the sets sold for this, I am concerned about centering of the con rods and pistons in the bores.
I do not know how to go about measuring this.

As far as I know the case halves match (how does one tell?) but the crankshaft is from a different engine
The little number on the front of the case is 805 and number on the crank is 795.
Advice please!


1966 BSA Lightning
(2) 1967 Triumph "Choppa"s
1974 Indian ME125
1960 Harley Servi-Car
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Re: A-65 excessive end float
Nick H #794353 12/30/19 5:25 pm
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Sounds like you have different case halves as the numbers should match. Although you fitted a new timing side bush and had it line bored perhaps the cases or bearings aren't seating well with each other and as you tighten the bolts suddenly the clearance increases?

Last edited by gunner; 12/30/19 5:28 pm.

1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
Re: A-65 excessive end float
Nick H #794355 12/30/19 5:38 pm
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The case matching numbers are usually on the lower mount, same numbers each side if its a matched pair.
Ar you using the shim cup, ? if not that might be why you have more than you think necessary.

in theory the crank number is subtracted from the case number to get required shims, that was the factory way, most folk just test it to see.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A-65 excessive end float
Nick H #794361 12/30/19 7:10 pm
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Nick H Offline OP
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Nope, case halves are a match. Thanks for that info.
The shim cups measure about .018-.020. Even with a shim cup and all three of the shims in the parts book (.003, .005, .010) you would have .038" of shims. I have .085"

A shim cup, by the way, I think is needed to keep the shims from shifting around as the shims I.d. is larger than the crankshaft.
I thought I'd be smarter than BSA and order shims with a close fit I.D. of 1.125". Then I discovered the crank has a fillet, of course which would keep the shim from being flush with the flywheel.
What I did was Dremel the inner edge of the shim at an angle so that it fits flush. I could do that because my shim is so freaking fat. Standard shim sizes - use shim cup and stock parts.

Still need to know how to tell if my con rods and pistons will be centered in their bores.

I've read all the past posts on this and I know the simple answer is to use the ball bearing but I'm hoping the roller may better control the crank flexing. Is this true or something I made up?
The issue is complicated by early and late ('66-'72) cases and cranks. If my fat shim is pushing the crank too far timing side what would the remedy be? Shim the timing side next to the thrust washer (mine is new btw) ?

Last edited by Nick H; 12/30/19 7:50 pm.

1966 BSA Lightning
(2) 1967 Triumph "Choppa"s
1974 Indian ME125
1960 Harley Servi-Car
Re: A-65 excessive end float
Nick H #794368 12/30/19 8:30 pm
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The parts book is handy but its not Gospel, it may well be that some motors need more than 3 or more of the thick shims.
To put your mind at ease test assemble the crank with rods fitted , with your desired end float set up, temp fit barrels with no pistons, each rod will move laterally on its big end, push to either side and measure gap between rod end and bore, try using sockets for plug gauges if you need to. it doesnt have to be bang on, there is some end float in the piston pin and the big end, so long as the rods are not way over to one side or the other it should be fine.
If you find the shaft is too far over to one side adjust the timing side thrust washer and add shims to drive side or visa versa, not sure how you could make the TS washer thicker, might need a one off Over thick one.
According to my books , 66 was when the crank changed from ball to roller type and the timing side thrust washer was introduced, also the sludge trap changed to a blind hole with a single plug on the timing side.
If your crank has a sludge trap access plug on each side it is an earlier ball type.

its not unusual to need more shims than you think , rubbing thrust surfaces wear, thicker shims take up the wear.

Last edited by gavin eisler; 12/30/19 8:40 pm.

71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
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MZ TS 250
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Re: A-65 excessive end float
Nick H #794381 12/30/19 10:41 pm
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Nick "The shim cups measure about .018-.020."

that sounds way to thin ....are u sure its the right shim cup ...........from memory they are about 1/16th inch ..........62 thou roughly ..........sounds to me that might be the issue.........lets see if anyone measures and posts an actual measurement

i gave up on shim stacks and always make a one piece spacer these days .........but admittedly you do need some gear to do that


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
Re: A-65 excessive end float
Nick H #794382 12/30/19 11:06 pm
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I haven't used the beezer shim and cup arrangement for a while now.
Just use parted off spacers and file the id to accommodate the radius.
The crank may need a couple of mill each side if it's a different type.
With the late ts thrust washer you may have to ditch that item and use
a bronze thrust washer made up to run on the steel of the ts bush.
If it's an all bronze bush, use a steel thrust washer. They don't need
to be anything flash, just good old bright mild or leaded bronze is fine,
there is little load on them.
Measure across the centres of the big ends (the oil holes may be that)
Halve the figure then scribe the flywheel, that is your centre. The case
split is normally accurate but you can measure the bore centres and then
from centre to outer bolt centre to check the bores. It's a bit of a pain to
go through but if you are mixing bits it's the best way. Getting the crank
central makes for a nicer lump really, as far as vibes an longevity goes.

Re: A-65 excessive end float
NickL #794389 12/31/19 12:00 am
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Originally Posted by Ignoramus
Nick "The shim cups measure about .018-.020."
that sounds way to thin ....are u sure its the right shim cup ...........from memory they are about 1/16th inch

I have an early type shim cup that measures .018". It won't fit the roller bearing. Could you be thinking of the timing side thrust washer which is 1/16"?
Originally Posted by NickL

With the late ts thrust washer you may have to ditch that item and use
a bronze thrust washer made up to run on the steel of the ts bush.
If it's an all bronze bush, use a steel thrust washer.

Good idea but why the differing metals? Are you thinking about galling? You do know the thrust washer does not spin.

I don't think the full story of the A-65 bottom end has been told yet, or at least I can't find it. CBS has a pretty good tech article.
From CBS, I know the "late" crank has a wider counter-weight on the left. Mine has equal counter-weights which would make it "early" but it has a single sludge trap, much like my Triumph crank.
I think this is where my extra space is coming from yet in all my thread reading I don't recall hearing of the same situation.

No recollection of how thick those home made spacers were?

Last edited by Nick H; 12/31/19 12:08 am.

1966 BSA Lightning
(2) 1967 Triumph "Choppa"s
1974 Indian ME125
1960 Harley Servi-Car
Re: A-65 excessive end float
Nick H #794393 12/31/19 1:18 am
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There are 2 types of shim cup as the bearing changed later on.

Rather than making a thicker ts thrust which sits fixed in the case you can just make
a large washer of bronze that runs on the steel bearing outer and the small machined
area on the crank. If however the ts bearing is an all bronze type the washer must be fixed
or some other arrangement sought. You shouldn't really run bronze on bronze although
as there is so little load on it it probably wouldn't matter.
To make life easier these days for a street motor, just use a ball race on the drive side.
I doubt it will wear out in 50,000 miles.

Re: A-65 excessive end float
Nick H #794398 12/31/19 1:40 am
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Originally Posted by Nick H
I know the "late" crank has a wider counter-weight on the left. Mine has equal counter-weights which would make it "early" but it has a single sludge trap, much like my Triumph crank.
I have one of those as well, from a 1965 Lightning Rocket.

As Gavin noted above, the parts books aren't always 100% definitive.

Re: A-65 excessive end float
Nick H #794401 12/31/19 1:56 am
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Originally Posted by Nick H
[quote=Ignoramus]Nick "The shim cups measure about .018-.020."
that sounds way to thin ....are u sure its the right shim cup ...........from memory they are about 1/16th inch

I have an early type shim cup that measures .018". It won't fit the roller bearing. Could you be thinking of the timing side thrust washer which is 1/16"?
[quote=NickL]

yes Nick you are right i probably did get that 1/16th in my head due to thinking about the thrust washer ........sorry for confusion


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
Re: A-65 excessive end float
Nick H #794406 12/31/19 2:15 am
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It was only the very early cranks that had the 2 plugs (also a different thread) on the sludge tube.
As i've said before, any of the cranks can be fitted to any of the cases but the degree of pi$$ing
about is the variable. A lathe and some bronze stock along with dial gauge and squares etc are
required, a good vernier also. You cannot just say you need a 60 thou spacer in the drive side as
every one is different. Most blokes who have built these engines from parts will testify to that.
For the average bloke, it's probably worth while taking the bottom end to an engineering shop and
getting the job done.

Re: A-65 excessive end float
Nick H #794454 12/31/19 1:50 pm
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Originally Posted by Nick H
As far as I know the case halves match (how does one tell?) but the crankshaft is from a different engine
The little number on the front of the case is 805 and number on the crank is 795.

Could it be you have an earlier "narrow" crank? It doesn't sound like this is the case based on the numbers you listed but check the width of the two bobweights. Before 1966, both weights were the same width but this changed in 1966 and the drive-side weight is larger.

You mentioned torquing the rotor nut down but are you checking endplay with the case halves fully torqued?

Re: A-65 excessive end float
Nick H #794455 12/31/19 2:02 pm
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No "average" blokes here.

Yes, it's clear now I have an early crank and late cases and need to make up the .06 on the drive side.

Last edited by Nick H; 12/31/19 2:06 pm.

1966 BSA Lightning
(2) 1967 Triumph "Choppa"s
1974 Indian ME125
1960 Harley Servi-Car
Re: A-65 excessive end float
Nick H #794470 12/31/19 5:20 pm
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If you dont want to shim on the crank , shims can be fitted behind the drive side main outer, this way they are static and cannot get chewed up or spat out.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A-65 excessive end float
Nick H #794481 12/31/19 7:00 pm
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Originally Posted by Nick H
Yes, it's clear now I have an early crank and late cases and need to make up the .06 on the drive side.

Okay, now that you've identified this, the fun starts:

This may not be a huge issue but is worth a check. The early "narrow" cranks are designed to be shifted a bit under 1/16" to the right (no room for a thrust washer in those cases) so the drive-side shaft is longer to compensate. Once you've got the crank properly positioned inside the cases, you'll need to play around with the spacer and shims behind the drive sprocket to ensure it lines up with the clutch basket and places the alternator rotor properly inside the stator.

Spacers
68-0686 .330" - .334"
68-0687 .311" - .315"
68-0688 .295"

Shims
40-0066 .010"
40-0069 .015"

Note that these shims are the same as those used against the crankshaft on unit singles and are available in sets just like the twin crank shims are.

Re: A-65 excessive end float
Nick H #794485 12/31/19 7:10 pm
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The required shimming on my all-original '67 A65 was .026". The shim cup thickness was .018".

The distance between the outer faces of the web differs between early (pre-'66) and later ('66-on) cranks. But I thought the pre-'66 crank was wider (longer?), since the earlier ball-bearing setup did not require that thick thrust washer on the timing side.

You DO have a thrust washer on the timing side, yes? (Sorry if this is too obvious a question.) To my knowledge, the crankcases early and later are the same.

Sounds like Gavin's suggestion is the way to go; fit the barrel and measure the rods left to right in the bores.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: A-65 excessive end float
Nick H #794488 12/31/19 7:38 pm
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I thought NickL s centre line on the crank was a better idea, cant vote for myself.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
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Re: A-65 excessive end float
Mark Z #794519 01/01/20 1:09 am
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MarkB: Thanks for something more to worry about!

Originally Posted by Mark Z

You DO have a thrust washer on the timing side, yes? (Sorry if this is too obvious a question.) To my knowledge, the crankcases early and later are the same.

I do. I'm now considering fabricating a thicker bronze thrust washer. My timing side bush is all bronze.

The early and late cases are not the same. See the CBS tech notes:
https://www.classicbritishspares.com/blogs/news/early-vs-late-cranks

I don't understand the part about "distance to gasket surface" at the bottom of the page by the photos
Are they saying the entire left case from center joint to bearing is (.041"-.056") greater in the later case?

...making my head spin!

Last edited by Nick H; 01/01/20 1:13 am.

1966 BSA Lightning
(2) 1967 Triumph "Choppa"s
1974 Indian ME125
1960 Harley Servi-Car
Re: A-65 excessive end float
Nick H #794543 01/01/20 9:47 am
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The early A65 timing side bush is different from the later bush the early bush has a thicker flange this could be why you have such a big clearance with an early crank.

Re: A-65 excessive end float
Nick H #794559 01/01/20 4:05 pm
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Originally Posted by Nick H
Originally Posted by Mark Z
To my knowledge, the crankcases early and later are the same.

The early and late cases are not the same. See the CBS tech notes:
https://www.classicbritishspares.com/blogs/news/early-vs-late-cranks


Yes, thanks for that. This article pretty much lays out "the whole story", and, as you commented, "makes my head spin".


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: A-65 excessive end float
Nick H #794603 01/02/20 1:38 am
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Post-65, the difference in the left side case is two-fold:

1. The inside case surface is machined to allow the later crank to shift to the left, away from the thrust washer

2. The bearing lip is machined to move the bearing outward as well (otherwise the machining in #1 would cause the bearing to stick out beyond the machined face).

#2 is what is causing you grief when setting endplay while using the early crank. The bearing is farther away from the narrow crank by about .060".

Good luck.

Re: A-65 excessive end float
Nick H #794615 01/02/20 7:53 am
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It's just a matter of making up spacers, why all the complication and worry????
Get the crank central and then measure the offset each side. To do
this just use a dti on the end of the crank, that will tell you how much each side needs.
It doesn't really matter what size the crank or cases are, it's the same procedure.
Once that's done, you need to space the drive side to align the clutch basket.
A steel rule is all you need to do that. Then the rotor that's even easier.

Re: A-65 excessive end float
Nick H #794621 01/02/20 3:19 pm
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NickL: Just how do I best "get the crank central"? Measuring from where? Any tips or tricks?
Fortunately there is a lot of play on the small end and some on the big end so how critical is it?
And what type of spacer do you suggest for next to the thrust washer where it is needed?
Your previous post you suggest a bronze spacer made in a lathe.
I may attempt to fabricate a new thrust washer by hand from a bronze washer - no lathe.
Sorry if i am overcomplicating this.

Last edited by Nick H; 01/02/20 3:25 pm.

1966 BSA Lightning
(2) 1967 Triumph "Choppa"s
1974 Indian ME125
1960 Harley Servi-Car
Re: A-65 excessive end float
Nick H #794622 01/02/20 3:51 pm
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Read the thread again, Nickl gave a good method earlier.

I custom make shims with no lathe , a diamond 400 grit oil stone, some good 20s -30s blues , oil and a figure of eight lapping motion, takes off about a 1/2 thou per song.
Having a spare old drive side main the same width but sanded on OD and ID for easy fit makes the measuring process a bit easier.
Googling " Bronze thrust washers" provides multiple sources all sizes from around the world, maybe Mc Master Car ( Sp?)in the US, that name comes up a lot here. Once you know what you need get something around 5 thou oversize then lap to suit if you cant get an exact fit for what you need off the shelf.

Last edited by gavin eisler; 01/02/20 3:56 pm.

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56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
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