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Old 04-01-2011, 05:06 PM   #1
airheadpenguin OP
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Airhead rocker needle bearings

Today I was rebuilding the engine on my R80 and following the instructions in the book to ensure that the rocker shaft was properly oriented and what not. This led me to pull the shaft out of one of my rockers only to find out that the bottom flange on the lower bearing race had a section that was missing. The result, a number of the needles fell out and it was a PITA to put back together.

Like any good engineer I said hmmm I wonder if the others are similarly messed up. Sure enough there were 2 more that had a similar fate, always the lower race and always the outside flange.

Now this is clearly not an uncommon problem since you can buy new individual races for $25 but a few questions come to mind:

1) What are the likely causes?
2) Should I care?
3) What's the best approach to replace them aside from a hammer and a drift (I'd like to avoid replacing both races in all 3 affected rockers)?
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Old 04-01-2011, 05:30 PM   #2
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The whole rocker arm assembly with 2 new needle bearings sets already in them are about a hundred bucks. Otherwise a press (or vice) and an appropriately sized socket is a workable way to get them in and out. Some heat on the rocker arm helps I think because its a tight fit. Its a pain in the ass to deal with the bearings in there, and heat, and press, though. Not too difficult for real men, but I found it tedious, and actually think I found a used arm with bearings in them for the same price as a new bearing at Re-cycled or something.

I dont know why they fail, but the cages are not super tough. Your racker arm shafts are not egged in any way? I doubt they are, I was just wondering.
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Old 04-01-2011, 07:53 PM   #3
zenben
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They'll run just about forever if you just put the needles back in.
If you lost a needle, then you have a different problem, but replacement isn't going to fix much.
At only a few thousand miles on new bearings the needles will start dropping out again. The time honored solution is to stop losing needles and move on.
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Old 04-01-2011, 08:23 PM   #4
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Good to know, all the needles are in so I guess I'll pretend none of this ever happened and ride the girl.
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Old 04-01-2011, 08:44 PM   #5
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The bearings should be available from an industrial bearing supplier for under $7. Removing and refitting is fairly straight forward. If it makes you nervous any decent auto shop or engine re-builders shop etc could/should be able to take care of it for you.

I'd be nervous about ignoring it with the damage already evidenced in your bearing cage.

ymmv,
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Old 04-01-2011, 09:27 PM   #6
Bill Harris
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Quote:
The bearings should be available from an industrial bearing supplier for under $7. Removing and refitting is fairly straight forward.
One would suppose, but no such luck. Last year, here (or on the Airhead List) the idea of off-the-shelf replacements came up and I did an exhaustive search using the bearing number and came up with nada It is an odd bearing (something like 14.5mm ID/shaft) with no direct x-refs. Which is why they have to charge $30 for it. On the design they could have bumped the shaft size up or down a hair, but noooo, they had to be Teutonic about it.

Let me dig around and find my notes and references...
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Old 04-01-2011, 09:31 PM   #7
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What I've seen so far is $25 list from BMW USA or 8.5GBP from Motobins. From Motobins it comes out to be about $35+shipping for all 3. That kind of pricing I can live with but this is clearly a case where BMW means Bring My Wallet.
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Old 04-01-2011, 09:32 PM   #8
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i had a similar problem finding replacements. I chalked it up to me not being able to measure properly, but the ones I ordered did not fit. Good thing they were only a couple of bucks.
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Old 04-01-2011, 09:51 PM   #9
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Only a few thousand miles and the needle will start dropping out of new bearings? This has happened more than once?
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Old 04-01-2011, 09:54 PM   #10
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In my case I have x32,000 on mine, what the x represents is anyone's guess but it seems likely to be 0 based on other things I've seen. I don't have enough experience to comment on the general longevity of the part but 32k seems low but you'd have to want to look at these to see this.

That is of course assuming that people don't take their rockers apart to inspect the bearings and shafts
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Old 04-01-2011, 09:56 PM   #11
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Quote:
Originally Posted by Bill Harris View Post
One would suppose, but no such luck. Last year, here (or on the Airhead List) the idea of off-the-shelf replacements came up and I did an exhaustive search using the bearing number and came up with nada It is an odd bearing (something like 14.5mm ID/shaft) with no direct x-refs. Which is why they have to charge $30 for it. On the design they could have bumped the shaft size up or down a hair, but noooo, they had to be Teutonic about it.

Let me dig around and find my notes and references...
No kidding? I'm pretty sure I had a match on it a couple of years ago from a local supplier.

Let me see if I can come up with something next week. Don't be afraid to remind me.

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Old 04-01-2011, 11:43 PM   #12
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That would be awesome Lornce. I think rockerarm maintenance is an important part of doing a valve job. I change them when I do valve jobs. I think the bearing needles get flats. That or the cages. You can feel it. It definitley isn't the shaft.

Ahp, I have seen them fail in 32000 miles but they usually last much longer than that. I have taken them off many a bike for a valve job and they are very often not broke. I would definitley say most often for sure in my experience but I do see them break on a semi-regular basis! IMO, they are still light years ahead of the bushed arms.
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Old 04-02-2011, 12:37 AM   #13
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I spent several years working in the bearing industry, and tried to find replacement needle rollers by checking every cross-reference I could find. I never managed to find anything which was a direct replacement. There wasn't even much that was close (from memory) which didn't involve a lot of extra work. I'd be very keen to know if that has changed.
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Old 04-02-2011, 01:55 AM   #14
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A point that I think many are missing, is the "Gap" in the bottom lip on the bottom bearing, this should NOT be there.

In my experiance this comes from the rockers being maladjusted for long periods, allowing the rocker to accelerate up and down along the shaft, between the pillow blocks.
This pounding of the rollers against the bottom lip of the outer race, eventually breaks the lip out, usually in line with the slot in the pillow block.

This is what I think has happened to your rockers.

If not discovered the rollers will make their way out of the rocker, and down the pushrod tube, to the sump.
They won't do any more damage, but isn't as it should be.

This leads me to another subject, how to make the boxer rockers quiet.

IMHO most of the tappet noise comes from the rockers moving up and down along the shaft, not by tappet clearance as such.
BMW must have thought this as well as the later boxers had plastic shims to minimize the end float.

On early boxers, I do the same thing by knocking the pillow blocks together, without loosening the head studs first, just fit a socket over the shaft and smite with a hammer, top and bottom, until there is no lateral movement.

So the bottom line is the needle rollers need to be replaced.

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Old 04-02-2011, 06:05 AM   #15
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A very good observation about what likely causes the needle break-out, Andy.

Quote:
Originally Posted by Andy-Gadget View Post
On early boxers, I do the same thing by knocking the pillow blocks together, without loosening the head studs first, just fit a socket over the shaft and smite with a hammer, top and bottom, until there is no lateral movement.

Or just hold the opposing pillow blocks together with your fingers, eliminating any end float, while you lightly snug up the cylinder stud nuts before torquing.

Max, appreciate your experience and input. I might be imagining things or confusing it with something else. Working from memory is always a dodgey business, but I was sure I was onto something or had heard from someone who was. I'll see what I can find next week and get back one way or another to the boxer collective.
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