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#668717 09/24/16 12:53 pm
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Can anyone tell me what the correct thickness should be for the engine shaft shim ...drive side...part # 66-661. There was no shim in the location when I got this project .... a packet of assorted shims came with the bits and pieces.

Thank you,

James.

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James: The shim measures 0.0195 inches and the space it goes into is about 0.034 inches deep.

This should be what you are talking about;

[Linked Image]

This is shim in place before the bearing goes in.

[Linked Image]

Here is a link to forum member Swan's project and his shim installation and the different shims.

http://www.dotheton.com/forum/index.php?topic=20929.360

see page 29


Gordo

Last edited by Gordo in Comox; 09/24/16 6:43 pm. Reason: wrong thickness

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That is perfect Gordo ... thank you!.
What is the purpose of the shim ?.... .0095" in a .034" deep pocket leaves a lot of " wiggle " room.

Thanks again,

James.

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I believe it acts as sort of an oil seal as it floats in that area. I think a one sided seal on the bearing would work a lot better.

I added a link above on the installation and please note I have corrected thickness to 0.0195 inches (typo)

Gordo

Last edited by Gordo in Comox; 09/24/16 6:51 pm.

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Thanks Gordo ... not much of an oil seal ! .... I have a bearing with a seal on the outboard side which I will be installing ... maybe leave the shim out?.

Thanks again.

James.

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James: As I recall other folks have used a sealed bearing. I would think that the original shim would be going back and forth as the cases cycled from negative to positive pressure as the piston goes up and down. The positive pressure would push the seal tight against the case so the leakage might not be too bad and it does fit quite tight on the shaft.

Gordo


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Well ! ... that is some fairly smart thinking from the BSA engineers !.

Thanks for the input Gordo.

James.

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Hi James, although 66-661 is described as a shim, in my experience it would normally be described as an oil slinger or flinger, depending on the manufactures terminology, It is trapped between the ball race and spacer 65-2528. The only time it would be likely to make contact with the case, is when the drive side nut has become loose.

Re fitting a single side sealed bearing, it is obviously a matter of your choice, but in my experience when fitting one, it created pressure in the primary cover due to the seal in the bearing acting as a check valve, causing a severe leak at the clutch sliding plate felt seal, necessitating a breather in the primary cover to cure the problem. After fitting an open bearing at a later date, the breather was removed and no leak experienced. As I understand it, sealed bearings are sometimes used, but as to any primary leaks I don't know. Thinking about it after this experience, I don't see the need for a seal at this point, unless running an open primary.


Brian

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Hi Brian, thanks for your reply and advice, I had seen in some other postings that owners had used a bearing with a seal on the outboard side ...perhaps they had already made a breather mod., not wanting to compound the already aggravating issues I may pop the seal out and go with an open bearing per the original design.
I will be posting a couple of photo's later today of the timing side case ... I would like to get some opinion as to what best to do.

Thanks again,
James.

Photo's of the timing side case showing some damage below the bearing from an escape attempt by the timing side shaft at some point in the history of this engine..
[Linked Image]
[Linked Image]
My problem now is without a .050" shim between the roller bearing inner race and the damaged area I am unable to reduce the end float of the crank, with .050" I have zero end float, the crank turns smoothly ....but the con rod is off centre by .030" toward the drive side ??.... I must admit to being thoroughly perplexed as to what to do. Welding and re machining the damaged area is far out of my budget ...even if it could be accomplished without distorting the surrounding case.
Can any of you knowledgeable fellows give me some advice please.
Thanks for any and all advice.
James.

Last edited by limeyrider; 09/25/16 12:16 pm.
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Hi James,
A couple of points.
It would be normal to expect the con-rod to pull up centrally on the crankcase join. If you're off by .030 that's more than you want and I imagine that the culprit will most likely be wear in either/ both of the drive-side spacers. I have a selection of 'under-sized' spacers all caused by the cush-drive nut being loose and the spacers simply wear away being made of nothing special steel. There's a racing fella on EBay UK selling high-tonnage spacers or simply get some new ones from your normal sources.
Secondly I would declare your notion of not getting the timing side case repaired a bit risky given the weakness that it clearly shows with the web missing and some cracks. Save up your pennies and get the job done properly by a specialist. If the remaining case web fails it's likely to be catastrophic and the preventative repair bill would be looking like a complete bargain. It's simply not worth the risk in my view.

Generally the issue of the amount of float on the crank, assuming it's pulled up correctly on the drive-side, makes me scratch my head though. By design the cush-drive should be kept tight and secured appropriately. But given that there is often a considerable amount of 'unsecured' end-float with the cush-drive nut loose I wonder if a good plan is to shim out the timing side bearing to, say 0,050" end-float, just in case the cush nut works loose and then there would be far less room for the crank to travel before it hits the lip of the roller shell. ie. if the travel is reduced is any 'contact damage' with the shell lip likely to be more benign than when being allowed to travel with 'full float". I'd be keen to hear any views on the subject.

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James, disregarding the condition of the case. If the crank needs to go over .030" this amount is required on the drive side. This is why I said I make a 65-1396 of the size required to avoid the use of further shims, but if you go for shimming, I would aim for one shim, rather than multiples. If the crank had zero end float with the .050" shim behind the timing side outer race. Remove it an put a .010" shim behind the inner race on the timing side main-shaft, this in theory should give you .010" free end float, (I would put this as a max figure) putting the rod in the centre, and letting the outer race .050" further into the housing.
If the timing side bearing is not a tight fit on the shaft I would use high strength bearing fit, especially with a shim behind the bearing.

The damaged case is a matter which I think requires further discussion.
PS
I will probably get sent to the naughty step for mentioning Loctite.

Last edited by DBDBrian; 09/25/16 1:56 pm.

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James: After my morning coffee it dawned on me that the 661 shim would be held tight against the bearing as Endo states above if the cush nut is properly tight. I have attached a photo of the bits to correct my mistaken views.

On the left is the 661 shim that goes against the bearing, in the middle is the distance piece 65-2528 that goes through the opening in the cases to push on 661 and on the right is one the 66-1707 or 1708 alignment washer used to establish the position of cush drive bearing.


[Linked Image]

I have been looking at too many non-assembled cases with the 661 shim floating inside the case.

For reference this photo shows how much the 661 shim covers the bearing. It should be spinning with the crankshaft as it is pressed to the inner bearing race.

[Linked Image]

Gordo


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To clarify my earlier point, if the crank is pulled towards the drive side it is likely to be due to wear in 65-1874 and/ or 65-1396 which occurs when the engine is consistently allowed to run with a loose cush-drive and 'chatter' occurs. Any shimming on the timing side is a different discussion as all of the the action starts on the drive side.

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Thank you Endo, Gordo and Brian for your replies,much appreciated.
Endo I hear your advice regarding the repair, finding a " specialist "
other than Phil Pearson may prove tricky.

Thanks Gordo, none of the shims in my collection are as you describe, at least now I have some idea of what I need.

Brian, I may not have been clear in my description, the .050" shim between the roller bearing inner race and the timing case,not the bearing outer race, the outer race is in it's usual location.

Thanks again for your advice,

James.

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If the cases have to go to Phil for repair at least you can be sure of the bike pulling at least an additional 5 to 10mph afterwards smile

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btw, these are the drive side bearing/crank spacers I was referring to earlier, high strength versions, EBay item 172341212884


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Hi James, yes apologies, I misread your post, I did not imagine a shim in this position, I cannot understand the P/O thinking behind it. If the rod is .030" off centre towards the drive side with the nut tight, then my previous post re centering would still apply. As Endo says the drive side is the controlling factor. As too the timing side, with the outer race home in the case, and the inner race up against the flywheel, (no shim) the free end float needs to be measured with the nut loose. If the reading is in excess of .010" a shim is required behind the inner race, as mentioned. I would aim in the region of .005" min .010" max. If there is no free end float when the rod is on centre, this would have to be investigated. One possible cause, is the crank pin not seating on the shoulders.


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James. Some points for positioning crank.

This shot shows the distant collars that position the bearings on the crank. The bearings go in the two spaces between the collars.

[Linked Image]

Once the outside ball bearing is set into the case and secured with the circlip it becomes the key to the crank position. The cush nut through the other bits outside of the ball bearing pulls the crank tight up to the inside of the bearing. Assuming that the bearings are correct the only variable is the thickness of the two collars shown below. These examples measure from left to right
0.6025 inches and 0.314 inches. What do your collars measure?

The crank should be centered when the cush nut is tight.

[Linked Image]



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Thanks Brian and Gordo ...I'm gathering quite a library of reference !.
I will have to disassemble the motor again to get the measurements Gordo ...but I know that the large spacer ..with the 15deg. taper ...measures .178" ... bridging the worn area, that is quite a lot different to what you have ?.

Thanks again,

James.

PS ... just how to close to "centred " should the rod be ? is there a tolerance + / - ?

Last edited by limeyrider; 09/25/16 5:52 pm.
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Maybe I was sent the wrong part as your measurement seems to agree with DBDBrian on your other thread. I will go back to the parts bins.

Gordo

PS. when I look at the earlier engine (late ZB and BB small fin engine) parts diagram they show a different part number for the collar, 65-1398 which is what I would have ordered.

Now I will to compare the early and later cranks to see if I can find any difference that would account for the different size. The smaller diam collar has the same part number.

Gordo

Last edited by Gordo in Comox; 09/25/16 7:28 pm. Reason: update

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James, the rod will have side clearance on the pin, with the crank in place and the nut tight, push and hold the rod at the big end (not the little end as the rod will tip) in both directions on he pin. You can then ascertain by eye, a mean figure as to the centre line of the rod with the case joint. This is not over critical, I would aim for no more than .005" off centre either way. As said with a purpose made 1396 you can get it spot on, without the use of shims. But I fully understand you don't have this facility.


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Hi Brian,thanks for that info., hopefully I can get a final length measurement for the 1396 spacer and find a shop to make me one ...I sure do miss my toolroom !.

Thanks again,

James.

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Even though the crank assembly is pulled up hard to the drive side and the end float should be minimal with all the spacers and shims, I would think you need to get that case repaired before any of this is even considered. A bit of putting the cart before the horse methinks.


Bill B...


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Thanks Bill, I'm not entirely surprised by the advice given .. having gone through all of the steps outlined by Brian and Gordo I have the rod centred ..spot on,crank end float is .001" max..
The recommended repairs to the timing side case, plus the other parts necessary to complete the project are pushing this out of my reach and into e-bay territory.

Thanks again.

James.


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Originally Posted by limeyrider
The recommended repairs to the timing side case, plus the other parts necessary to complete the project are pushing this out of my reach and into e-bay territory
I hope it doesn't come to that. For what it's worth, the repairs to the timing case don't look difficult at all. If it were mine I'd install an old bearing in the housing to help minimize distortion and build up the missing metal with my TIG welder. The Al is pretty thin so distortion would be minimal anyway. The hole in the middle is there only for clearance of the shaft so it wouldn't have to be redrilled with much precision (unlike if it were the housing for the bearing itself). Hence, setup to machine it after welding wouldn't take much time.

North Carolina is the epicenter of NASCAR so machine shops near you must be almost as common as Baptist churches. If presented with a pre-cleaned case the entire job could be done in an hour so it should cost under $100 (I know, I know, $100 here, $100 there, and pretty soon it adds up to real money).

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