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Lost Semisphere!

Marlen Padberg

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Marlen Padberg

I posted this under "Winter Maintenance" for my camhead, but I've got a problem and I'm concerned!!!




Ok, I have a potential situation. Any for real BMW mechanics in the house?



Following re-assembly, I started my bike and the right-side cylinder made a ticking sound. Concerned me, so I shut it down, undressed it, and pulled the spark plugs to see if there was something unusual. Both looked good, I figured it was either a valve ticking or a plug coil arcing. Nothing to see there, so I took off the valve cover, and out falls a cam follower and circlip. Yikes!



The real crux of the situation is that I can't find the semisphere that goes in the cam follower. The semisphere is swapped out to adjust the valve gap. It would appear the semisphere fell out and ran with the oil down into the sump. I drained the oil, and didn't spot the semisphere, and it wasn't attached to the magnet in the oil sump. So I'm wondering where it went - I'm going to inspect the valve springs again and see if I can spot it there.



I'm thinking about the flow of oil. If the semisphere went down into the sump, then the only things down there would be the oil pump pickup (which has a screen in it, I believe),and the oil drain plug. I'm concerned that the semisphere might get caught in an oil galley or somehow restrict oil flow. I'm thinking I need to go fishing with a magnet via the oil galley or the oil plug. I don't think there's an oil pan per-se.



Thoughts? If I can't find the semisphere, would that be concerning? I don't know what size semisphere I need, so I would need to go and pick up a few, try them, set the valve lash, and return what I don't need, I guess.



I'm going to get a magnetic pickup tool and do some fishing. Hopefully I can find the semisphere. Any other thoughts on the matter? What else can I do?






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Evening Marlen


Personally I would definitely go looking/probing for it.


If that semisphere made it's way all the way to the bottom of the oil sump then probably not an issue (I have found all kinds of parts in the oil sumps of BMW boxers & none really seemed to cause any issues)


The problem could occur if the semisphere doesn't get all the way to the bottom & gets jammed in a cam chain or intermediate shaft.


Are you sure that it didn't fall out on the floor when you removed the valve cover?


Start your search with a very bright strong light by looking into all the cyl head nooks & crevices (everywhere)


If it got into the engine it will be difficult to find but not impossible. If no luck to begin with then maybe (with a helper) carefully lay the bike over on one cyl head then onto the other as maybe that will dislodge the darn thing.



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Marlin, let us know where you are and I think someone from the site would be happy to come over and help. Good luck with the search!

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Marlen Padberg

I'm in Edmonton, Canada. A little bit out of the way... But good news! I found the little rascal!




There it was! I found it wedged into a fastner in the head here:




I mounted the semisphere back in the follower, re-installed the follower and retainer clip, gave everything one last inspection, and valve cover back on. Poured the oil back in, started it up, and all is good again! Massive WHEW!!!! I was worried about that little sucker getting wedged in a timing chain and grenading the motor... Yikes!


All is good again... Nothing further to see here...



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Great news/too bad it's going to be rather a bit to cold for riding for awhile where you are. Enjoy next spring and summer. :thumbsup:


You have some very beautiful riding close by.

Edited by Marty Hill
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Why did the circlip come off? Did you not get it seated properly when you put it back on? I thought I read somewhere that you should put new circlips on when you take them off. I will be checking my valves for the first time this spring and I do not want to make the same mistake you did. With my luck my outcome would be much worse.



Roger L

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Marlen Padberg

I've heard that, but when I removed the valve covers to measure the gaps, they were all within spec, and I didn't need to remove anything. I think I dislodged the e-clip when I was putting the valve cover back on. oops!!! No damage done, and its all back together again.


I think the trick there is, the valve cover has a small lip on the top of it, and it will "hang" in place on that lip even with the fasteners loosened. When you're putting the valve covers back on, make sure the valve cover is over the lip and properly positioned. I think thats where I error'd. My bike has 45K kms on it, and all valves were comfortably within spec still. I've read that most shops rarely need to swap out semispheres because the twin cam head bikes valve gap rarely changes. Worth a check tho, just be careful re-assembling.

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