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Split cases and found this

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AZscrmblr
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Split cases and found this

Post by AZscrmblr » Mon Oct 23, 2017 10:31 pm

I had a hard time separating the upper and lower cases on my CB77 and couldn't understand why. I gently pounded in some little out of the way places and they finally separated. I found a tight fitting collar about half way up on one of the interior studs that prevented easy separation. I know the cases have been split before so it was left in place on reassembly. Does anyone know what this is for? Should I remove it or leave it in place? It is only on one of the studs.

e3steve
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Re: Split cases and found this

Post by e3steve » Tue Oct 24, 2017 2:19 am

AZscrmblr wrote:I had a hard time separating the upper and lower cases on my CB77 and couldn't understand why. I gently pounded in some little out of the way places and they finally separated. I found a tight fitting collar about half way up on one of the interior studs that prevented easy separation. I know the cases have been split before so it was left in place on reassembly. Does anyone know what this is for? Should I remove it or leave it in place? It is only on one of the studs.
That’s a locating dowel (knock pin) that was in the wrong place, I’d say... Study the Shop Manual for a better idea as to where they should be. Items 3, 4, 5 & 11 here:
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AZscrmblr
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Posts: 27
Joined: Sat Sep 16, 2017 7:29 am
Location: Phoenix AZ

Post by AZscrmblr » Tue Oct 24, 2017 9:18 am

I mis-stated where the collar is located in my original post. It is located midway up the threaded portion of the stud. It is threaded and screws on like a nut.
e3steve, thanks for the idea that it is a knock pin. If it were, wouldn't it be located at the base of the stud so that it could align the upper and lower crankcases. I don't see how it could help in aligning them when it is located at the threaded end of the stud.

DJM
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Stuck cases

Post by DJM » Tue Oct 24, 2017 4:07 pm

I think you might be looking at a crushed (aluminium) sealing washer which can compress onto the threaded part of the 6mm stud which passes through the main oil gallery. If this happens the washer can usually be screwed off the stud with a pair of pliers and the cases will then come apart. The washer should be replaced every time you split the cases anyway.

Stud 29, sealing washer 32 and sealing nut 31 on the parts diagram.

AZscrmblr
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Joined: Sat Sep 16, 2017 7:29 am
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Post by AZscrmblr » Tue Oct 24, 2017 5:11 pm

DJM - I think you may be right. It looks like it is made of the same aluminum as the sealing washer. What is puzzling is that it is on the stud opposite the stud requiring the sealing washer and special nut. Perhaps someone assembled the engine thinking both of these studs needed a sealing washer.

e3steve
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Post by e3steve » Wed Oct 25, 2017 5:04 pm

Don't suppose it could be a Helicoil, or similar, that's pulled out? Just a thought...

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