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wrist pin bushing upside down
#792925 12/14/19 7:15 pm
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Danam Offline OP
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let's have a contest to see how far a circlip can fly through the air whilst removing it < I will win >
anyhoo, I discovered on my 1970 A50 one of the small end bushings was installed with the hole on the opposite side of the rod hole. How bad is this and how can I check to see if this is reusable?

also, the bushing was a milimeter to one side and the pin does not easily slide into it, not sure if that matters

photo:
[img]https://drive.google.com/file/d/1LceQE4P3_2wPjkpHGGcCDQM6JT_F69Oa/view?usp=sharing[/img]

Last edited by Danam; 12/14/19 7:40 pm.
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Re: wrist pin bushing upside down
Danam #792927 12/14/19 8:55 pm
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Warm the rod & fit a new bush.
It was either badly installed or has moved during use
In any case they are cheaper than a second gasket set even if it does not cause major engine damage


Bike Beesa
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Re: wrist pin bushing upside down
Danam #792930 12/14/19 9:06 pm
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Its not really possible to say for certain but i would say it looks like the bush has rotated in the rod , going by the scoring marks that can be seen on the ID and the fact you have said its a tight fit to the pin.

It does matter , i would check to see if its a tight fit in the rod (give it a couple of gentle taps or a push with a mandrel (or an old bush if you have one) and see how easily it moves)

in any event it needs replacing and honing/reaming (the new one) to a good working clearance with the pin and a tight fit into the rod...they should be an easy but firm sliding fit on the pin

I cant see how anyone could have placed a bush with a hole so obviously misaligned with the oil hole in the top of the rod.

use some super strength lock tight or similar after carefully examining the ID of the rod for ovality or obvious scoring. obviously also make sure the pins havent suffered from lack of oil.


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
Re: wrist pin bushing upside down
Danam #792950 12/14/19 11:21 pm
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Hmmm. shoot me down but don't the bushings just come plain with no holes? Don't you press in the bushings then DRILL the holes? Seem to remember doing that on my B44. If that is the case then these things have moved in use and that sounds like it is going to be expensive.

Re: wrist pin bushing upside down
Dave Martin #792954 12/14/19 11:32 pm
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Originally Posted by Dave Martin
Hmmm. shoot me down but don't the bushings just come plain with no holes? Don't you press in the bushings then DRILL the holes? Seem to remember doing that on my B44. If that is the case then these things have moved in use and that sounds like it is going to be expensive.


no they dont generally come with no hole........but with some of the junk parts made these day i guess anythings possible .......all the ones ive ever seen or fitted are already drilled.....


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
Re: wrist pin bushing upside down
Ignoramus #792967 12/15/19 3:39 am
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The bearing/bushing surface looks OK to me.

Re: wrist pin bushing upside down
Danam #792979 12/15/19 5:25 am
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If the circumferential lines that I think I see in the pic are really there, the bush is junk. The bush should be perfectly smooth, as should the gudgeon pin surface be. It looks as if it has spun in the rod, but I suppose there's always a dafty who will stick it in any old way?

Re: wrist pin bushing upside down
koan58 #792983 12/15/19 9:36 am
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Originally Posted by koan58
If the circumferential lines that I think I see in the pic are really there, the bush is junk. The bush should be perfectly smooth, as should the gudgeon pin surface be. It looks as if it has spun in the rod, but I suppose there's always a dafty who will stick it in any old way?


The bush has walked also. When I first had my motor together it had new bushes in. 3000 miles later one had walked, the rods I have now don’t require having bushes fitted.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: wrist pin bushing upside down
Danam #792986 12/15/19 10:18 am
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I think you can safely assume that the bush has rotated and walked, the big question is what do you want to do about it.

A quick and cheap fix would be to pull the bush out, assess if the hole in the con-rod is serviceable and fit a new bush accordingly. The big problem with this is, reaming the new bush in situ so that the wrist pin runs in line and parallel to the big end. If it doesn't, it will inevitably start 'walking' again almost immediately.

The best solution would be to pull the motor apart and remove the rod from the crank and get the small end bush replaced by a competent engineering company. Even then, I have seen small end bushes replaced by so called 'experts' that ended up not running true. An easy check for this is by connecting two rods together using a wrist pin and checking whether they run parallel and true to each other.

If you want the Rolls Royce or as you would possibly say, the Cadillac solution, then fit new rods, either billet or steel capped that don't have separate bronze bushes for the small ends. imho, bronze bushes in alloy rods was never a good idea.


1957 BSA A10 Spitfire
1971 BSA A65 Firebird
1971 BSA A70 Lightning
1975 Norton Commando
1961 Norton 99
Re: wrist pin bushing upside down
Servodyne #792987 12/15/19 11:12 am
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Originally Posted by Servodyne
imho, bronze bushes in alloy rods was never a good idea.



Same here and I believe the same for steel rods. My 400/4 will rev over 10,000 and that doesn’t use bushes small ends. Don’t see why map are doing so?


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: wrist pin bushing upside down
Danam #793009 12/15/19 4:52 pm
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https://1drv.ms/u/s!AsKcYdC1qRK7jB2mhecfhV_Nv_vq?e=XNYgcn
https://1drv.ms/u/s!AsKcYdC1qRK7jl8OUVWhHkAPAWIs?e=f16OF3

The Honda chrome moly rods sometimes get the small ends looking like the one pictured. I have repaired several using high tensile thin wall steel sleeves (picture). Bronze would of course be better but because of having to be thin wall the right amount of interference fit cannot be used, bronze being too soft. My Ducati has bronze bushed chrome moly rods.

Please tell why bronze bush in alloy and steel rods is a bad idea. I think it is the best if there is enough material so the bush can have the right amount of interference fit (and so does Ducati and MAP). The early A65 had cast iron bushed alu rods which also worked ok even when cast iron needs to have a much greater interference fit than for example steel (and bronze)

Last edited by Arnstein; 12/15/19 4:59 pm.

Arnstein

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Re: wrist pin bushing upside down
Arnstein #793011 12/15/19 5:23 pm
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Originally Posted by Arnstein
Bronze would of course be better but because of having to be thin wall the right amount of interference fit cannot be used, bronze being too soft.

I think you just answered your own question. I have seen far too many bronze small end bushes in alloy rods that have come loose and walked. Norton's were also prone to this on the Dominators until they realised that running the wrist pin direct in the alloy was a far better solution all round. I can't say I've ever seen an alloy con rod with a cast iron bush even though I once had an 1963 A65.


1957 BSA A10 Spitfire
1971 BSA A65 Firebird
1971 BSA A70 Lightning
1975 Norton Commando
1961 Norton 99
Re: wrist pin bushing upside down
Danam #793023 12/15/19 8:33 pm
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Yes I answered if my question was regarding when a thin wall bush had to be used.

I also said, if the bronze bush has the right amount of material and therefore can have the right amount of interference fit it will be the better solution. Especially so in steel rods which is why amongst others Ducati has them.
Having new alu rods without in both my A65 engines I of course agree that alu rods works excellent without them, better than steel rods anyway. But you might agree there cannot be nothing against having them if done properly (wall thickness / interference fit).

Wish I still had the a65 rods with cast iron bush so I could send a picture..


Arnstein

BSA Spitfire MK3.800cc (also engine 850cc 90degree)
Honda CB450T -71
Laverda RGS 1130cc -85
Ducati 1098 -08
Re: wrist pin bushing upside down
Arnstein #793027 12/15/19 9:26 pm
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Originally Posted by Arnstein
But you might agree there cannot be nothing against having them if done properly (wall thickness / interference fit).

Perhaps I've just been unlucky in seeing bad examples on old British motorcycles. They could work perfectly fine in more modern machinery like Ducatis where machining and quality standards would be so much better.
The problem may not even be the original fitment by the factory but over zealous owners who want to replace the bushes but don't appreciate the precision required. Like replacing a valve guide and expecting it to perfectly line up with the valve seat.


1957 BSA A10 Spitfire
1971 BSA A65 Firebird
1971 BSA A70 Lightning
1975 Norton Commando
1961 Norton 99
Re: wrist pin bushing upside down
Danam #793028 12/15/19 9:26 pm
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Originally Posted by Arnstein
But you might agree there cannot be nothing against having them if done properly (wall thickness / interference fit).

Perhaps I've just been unlucky in seeing bad examples on old British motorcycles. They could work perfectly fine in more modern machinery like Ducatis where machining and quality standards would be so much better.
The problem may not even be the original fitment by the factory but over zealous owners who want to replace the bushes but don't appreciate the precision required. Like replacing a valve guide and expecting it to perfectly line up with the valve seat.


1957 BSA A10 Spitfire
1971 BSA A65 Firebird
1971 BSA A70 Lightning
1975 Norton Commando
1961 Norton 99
Re: wrist pin bushing upside down
Servodyne #793040 12/15/19 10:55 pm
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" Like replacing a valve guide and expecting it to perfectly line up with the valve seat " [/quote]

A very good picture of the behavior of a few of the "experts". Some are even giving "advise" to others in matters they really do not understand themselves.


Arnstein

BSA Spitfire MK3.800cc (also engine 850cc 90degree)
Honda CB450T -71
Laverda RGS 1130cc -85
Ducati 1098 -08
Re: wrist pin bushing upside down
Danam #793045 12/15/19 11:40 pm
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.
i would guess ... that the bush walked ... rather than being installed incorrectly .

like others have stated ,
from the one pic.
the inside surface looks scored ... some amount of oil contamination ... and an overheating related event .

but the picture is incomplete without showing us what the wrist pin looks like ?
... blued in the middle ?
.

Re: wrist pin bushing upside down
Danam #793054 12/16/19 4:15 am
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I don't have the time or resources to tear down the crank. I think I'll just replace the bushing and carry on. Thanks for the input!

Re: wrist pin bushing upside down
Danam #793058 12/16/19 6:46 am
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The only proper way to fit and ream a small end bushing is with the rod removed and set up on a machine. The small end to gudgeon pin fit is the tightest tolerance in the engine, about .0005", and the clearance must be uniform across its length and parallel to the big end.

I tried to have them done in situ once because I didn't want to tear down the lower. I just had the engine rebuilt and then discovered that the pistons I had sourced had gudgeon pins about .002" too large, and the pistons were too old to return. The machinist did his best to line-ream the bushings, using the old gudgeon pin and opposite rod as a guide, but he didn't charge me and said he would not guarantee the results. Sure enough, after the engine was together and running, the pistons rocked or thrusted sideways and made a noise akin to piston slap.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: wrist pin bushing upside down
Danam #793114 12/16/19 7:35 pm
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re: my last post about the bushes being supplied without oil hole and drilled in situ (and duely being shot down!) Just checked with The Blessed Rupert Ratio and he implies that they can be supplied either drilled or un drilled. Images on line are split about 50/50 drilled and un drilled. This begs the question of "why on earth would a manufacturer go to the bother of pre drilling the oil hole?" it is an extra manufacturing step that all it does is slightly complicate fitting. I think it is safe to assume that anyone capable of pressing out the old, pressing in the new, then reaming the new one to the correct size is more than capable of drilling a small hole in a bit of bronze!

Re: wrist pin bushing upside down
Danam #793118 12/16/19 8:26 pm
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Dave commented :
"This begs the question of "why on earth would a manufacturer go to the bother of pre drilling the oil hole?" it is an extra manufacturing step that all it does is slightly complicate fitting"

I suppose the answer to that could be that since all bike fixers arnt created equal there would be a percentage that upon getting their new undrilled bush would think

" oh i see it isnt drilled it must not matter" ........others probably wouldn't even notice .........people do strange things i suppose


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
Re: wrist pin bushing upside down
Arnstein #793120 12/16/19 8:31 pm
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Originally Posted by Arnstein

" Like replacing a valve guide and expecting it to perfectly line up with the valve seat "


A very good picture of the behavior of a few of the "experts". Some are even giving "advise" to others in matters they really do not understand themselves.

[/quote]

well that may be true , on the other hand some of the guys/experts on this forum have extensive engineering backgrounds .........takes a while to realise who those guys are but its possible


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
Re: wrist pin bushing upside down
Ignoramus #793143 12/16/19 11:07 pm
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Originally Posted by Ignoramus
Originally Posted by Arnstein

" Like replacing a valve guide and expecting it to perfectly line up with the valve seat "
quote Servodyne

A very good picture of the behavior of a few of the "experts". Some are even giving "advise" to others in matters they really do not understand themselves.



"well that may be true , on the other hand some of the guys/experts on this forum have extensive engineering backgrounds .........takes a while to realise who those guys are but its possible" [/quote]





Yes, it is possible to name some of the guys that must have extensive engineering background, and I am one of the guys admiring the work shown by them

Last edited by Arnstein; 12/16/19 11:19 pm.

Arnstein

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Re: wrist pin bushing upside down
Danam #793279 12/18/19 10:56 am
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Once again we have to remember we are talking about very old manufacturing technology of high speed steel tools moving between stops on a capstain lathe.
Followed by wet or dry grinding / polishing again with the tool moving between stops.
Thus no 2 will ever be exactly the same.
Not like today when the machine can be controlled in real time by measuring the pin while it is being machined plus applying temperature compensations also in real time.
Carbide tooling and much better grinding /polishing machines can pop out 10,000 pins/hr that are identical to within 0.00001

So at the factory, Mary would grab pin that had an "A" fit and try to find an "A" sized rod hole to poke it through.
When this happened , all was good but if she had nothing but "B" size pins and all "A" sized rods , then you get a bush which hopefully would survive till the first 30,000 mile bottom end rebuild.

Last edited by BSA_WM20; 12/18/19 10:59 am.

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