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Not really true, it fits nicely but without an idler pinion installed. My engine should be made in May 69, cover number is 71-1047 and it looks like it's later because it has a boss for a later clutch actuating mechanism, however earlier cover 70- something fits even worse, leaving 2 mm gap between it and a case. I checked an idler pinion with both covers and they don't interfere with nothing, it looks like boss for a pinion idler bush in those covers is 2 mm too high. I know for sure a pinion is part of my engine, covers are not.
To lower a boss in the cover I need a milling machine ( which I don't have access to ) so my question is what about turning a back of the pinion on the lathe, are they very hard? Did anybody had the same problem and solved it?

Last edited by Adam M.; 11/21/21 11:28 pm.
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There are 2 types of idler pinion, early and late.
early uses larger oil seal. later ones have machined outer shaft for smaller id seal.

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Pictures would be good. But the bushes are different one with a shoulder one without? Don't fit a shouldered bush in a later timing cover or case.


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Originally Posted by Mark Parker
Pictures would be good. But the bushes are different one with a shoulder one without? Don't fit a shouldered bush in a later timing cover or case.

Just what I going to say. 69 on crank cases should not have the shouldered type bush.

You then need the correct idler and pinion for the outer timing case.


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So this is an engine timing side

[Linked Image from i.postimg.cc]

Both covers:

[Linked Image from i.postimg.cc]

[Linked Image from i.postimg.cc]

And pinion which is a late type:

[Linked Image from i.postimg.cc]

I tried it with a seal and without, no difference. No shouldered bushes at all. Looks like a pinion is just to thick for these covers. I tried a pinion with covers only it doesn't interfere with covers at any place. Without a pinion covers fit nicely, with a pinion installed I have a gap in the front of the cover 0.065".

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It's one of 3 matching cases it's probably just not a matching one and in line. And the other case is the same or worse. The main cases are numbered as is the inner T/case because that idler is bored in line. The boss over the end of the crank has a number as does the R/h case above the lower frame bolt. They sometimes do and sometimes do not line up when you swap unmatched cases, so the pinion is at an angle and will not go in misaligned. Main cases are the same though main bearings are in line, cam bearings and gearbox to oil seal can be out, and the faces top and bottom.

Gears are a very precision fit. If it's wrong it can be rattly.

It only needs to be out a little bit esp if the bushes are good and it will not go together. If you see how it is you may be able to remove dowels and adjust it a bit and get it. Then bodge the dowels a bit to hold it where it needs to be. I've never needed to do that so I don't know how easy that would be. It may move a little on the screws if the dowels are out.


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I’ve done a few bikes with mismatched inner timing covers and never seen this issue. Even if you fitted an earlier pinion or shouldn’t cause it to punch.

The bush in the crank case isn’t flush with the case, it should be. However you would still want a couple of thou end float to ensure that there won’t be any binding.

Have you checked that the gear is positioned properly on the pinion? Also have you ensured that the oil seal isn’t all that’s holding the case off the pinion? (A long shot that one)

The shoulder on the pinion should be only as deep as the gear that is sitting on it, so if it’s not flush then this will cause an issue.


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Bushes of the timing case and covers are in line and engine turns smoothly without a cover or with cover on and screwed down so I decided to remove this .065" from a rear flat of a pinion and check how it will work. I believe with a gasket installed it will have enough clearance to work properly..

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It appears from the picture that your bush in the main case is proud of the boss. It should be flush. I think you are fixing the wrong thing.

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Yes it looks like that in a picture Dave, but it's flush - I checked.

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On a 71-1042 case the idler bush is 0.131" below the plane of the cover mating surface.

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Looks like the late type pinion is your problem, a wee skim in a lathe should fix it, later pinions got thicker.


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Another 'select on assembly' item i suppose.
I have put quite a few non matching cases/covers together,
you do sometimes have to mess about with fittings etc.
I tend to agree with Gavin, spin the gear up and take a bit off.

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This is what was finally done and cases fit together. Now to repair heavy gouges on the front of the timing case. What do you think about using JB Weld in this place and even it out with a file?

[Linked Image from i.postimg.cc]

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Fine, i've done similar myself, don't get it welded as it'll end up like a banana.


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