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For the C-clip source, I'd scan the items inside the front inner cover... around the cam chain. This because there is a direct passage from that area that lets items fall (harmlessly) into the oil pan. You can look at the parts microfiche on Max BMW and others. But be sure and look only at the fiche for your model year because small changes happen year-to-year.

https://shop.maxbmw.com/fiche/partsfiche.aspx

As for the crushing of the rubber end on the filter element... poop happens. In my mind, being crushed is the exact job of the rubber ends. There is no end sealing, without being smooshed. And because the bike is new to you, there may be no way of telling exactly how long that filter has been in place (thus the effect of long-term heat), or what quality level the filter is. In other words, if the previous owner installed a rip-off Chinese filter 10 years ago, then sights like this might be the logical result. With all due respect, I'd rather know... 'what brand marking are present on the filter ?' 

The OEM filters are either Purolator or Mann.

Thanks Richard. Unfortunately,  it looks like it came from the cam chain tensioner. That looks like alot of work. I wont run it until that is confirmed and corrected. 

I dont know what brand the oil filter was but I'm replacing it with a Mahle.

Thanks

Out of curiosity, I looked at the microfiche and also saw that clip. Bummer. I’m hoping that someone installed new parts, and that’s the old clip you found, that they lost by accident. Guess there is no way to know without opening the timing chest and looking, huh?  I can’t think of a way. It also looks like the spring could possibly keep the tensioner from walking off the post without the clip being there. Might be what has kept things from coming undone. Good luck!

It's easy to understand how someone could drop that clip and simply go get another. However, it's best to check since the bike is new to you. 

That's an easy, straightforward job for a novice. If you have a lift and an assortment of standard tools it will take you about 4 hours. You will however require a stator puller, which is a long bolt that threads down the center hole of the stator to pop it off the cam shaft. Being little more than a bolt, they are cheap and easy to come by. 

When you do that work you want to replace (or at least check) all these parts....

• 3 piece inner cover gasket

• O-ring at crank

• Oil seal behind alternator

• Alternator brushes

• Cam chain

• Moving cam chain tensioner blade

• Updated tensioner blade spring

• And of course the clip and associated parts

• This is also the best time to install solid rectifier mounting posts if you have the rubber mounts (Motorrad Eliktrik)

• It is also mandatory that you check the condition of the 3-position off-white connector coming off the ignition "bean can". These are bad to chip/ crack/ crumble/ turn to dust... and when that happens your ignition with stop. Motorrad Elektrik has replacement connectors that are easy to install while the bean can is off the bike. 

Only the white connector needs help. The black connector is always OK.

Be careful to first disconnect the battery since you'll be fooling with the rectifier board.

Hope this helps.

• Upon entering the inner cover, first thing you do is stuff a rag into the hole leading to the oil pan. Three guesses why you want to do this. ? 

• When you work on the cam chain the revised/updated tensioner spring has to be installed first. This photo shows how to hold the plunger in place and out of the way with a standard cable tie (the red one).

• Then you can use a small 3" cable tie (the back one) to draw up the 2 ends of the cam chain. This makes it super easy to install the connecting link without dropping more stuff into the oil pan. The masterlink clip is always installed with the closed end facing the direction of travel. (Think of it as a "fish swimming along".)

Simple tools for a simple task.

Good luck.

https://brook.reams.me/bmw-motorcycle-rebuilds/1975-r756-build-s-replica/11-bmw-r756-replace-timing-chain-crankshaft-sprocket-nose-bearing/

This Brook Reams article goes into great depth, far more than you will need, but it’s good with lots of photos. His is an R75/6, which should be very similar to yours with the duplex chain. As far as I know, your R75 doesn’t have a bean can, just good ol’ open breaker points. But, I could be wrong.

Can the newer plunger style tensioner spring assembly in Mr. Wobbly’s photo be fitted to the R75/5?  I am learning here also. 

Well, after checking the manual, I think this job is better left to a pro. I know the cam chain was replaced in 2013. I've ridden the bike a few hundred miles since purchasing with no funny noises and the previous  owner rode it several thousand miles. Am I being paranoid? Sure would be a problem if that tensioner let go.

When I checked the valve gaps, the left exhaust adjuster was stripped. Replaced that. The rocker bushings are worn as well as the the shafts with wear on the rockers too. There was some metal in the oil in the valve covers when I removed them. I tore apart the oil filter and it looked ok. Looking like a top end at this point on top of the tensioner issue. 

Might need to trailer  it over the mountains to Murph in Eugene. 

Thanks again.

► My bad on the white connector/ bean can. I was still thinking of a newer bike in another thread.

You simply have basic ignition points. You'll want to replace the auto advance springs and lube the unit. Refitting will require timing the ignition with a strobe lamp at high RPM and using the full advance timing mark. 

I always replace the moving tensioner arm with a cam chain, but not everyone does. Check it for wear. 

The tensioner arm spring update (if it applies to your model) may be new since 2013. Consult the Max BMW parts fiche and see if the update is for your model. Either way, a new spring isn't going to 'break the bank'.

You can easily do all the work I described, and I encourage you to do it so that you can intimately know your bike's condition and make all the updates. A shop is not going to generally do repairs until parts break, or you request. So items like the solid rectifier mounts are going to be passed over. But that's the type item that fails on the road and kills the rectifier board. So instead of $25 while the inner cover is off the bike, you may be required to take the cover off yet again AND buy the studs AND a new $250 rectifier board. And don't forget the towing fee, plus a night in a motel. I can easily see $1000 in spending because you didn't do the work yourself. YOU can plan the maintenance of your machine OR you can let your mechanic plan your next visit. 

The rocker arm bushes are another matter. They may require a hydraulic press. That probably is specialist work. Take him the 4 rocker arms and shafts. You install them.

Paranoid?  I keep wondering what I would do.  Keeping emotion aside, and applying purely reason, I would say all is well. You know that there was a new chain installed in 2013. So all that stuff was apart. Was this done by the PO?  Can they be asked if a clip went astray?  Logic says the clip you found is one that “got away”, and the person probably had no clue where it went. So, they got another, or used the old one. Very easy to imagine that happening. No one would loose a clip, then go ahead and put the engine together with NO clip. And, if a clip is snapped onto that post, its not going to fall off later and find its way to the oil pan. Once it’s on, it’s on, until pried off.  Then, you’ve got thousands of miles with no issue. 

Yet, there is that stinking clip. Why did I have to find that!?!  And I can’t know for absolute certain unless I look. It’s making me paranoid. Where is Superman when you need him?  Not helping, am I?  

I’d ride it.  But, that’s me.  To me, it’s much much more likely there are other possible issues lurking within the bike that you know nothing about (like ALL of our 40+ year old machines), than that clip being absent from its post. If that were an issue, it would have produced symptoms immediately (and long ago), I would surely think. Just my 2-cents. And that’s all it’s worth. 

You guys are great. I think I'll do the valve gear and let the clip go for now. When the snow melts, I will putt around the neighborhood to warm up the tranny and final fluids for a change. Listening for anything amiss. I won't ride farther than I can push.

I'll upgrade the diode board mounts as well. I want to take this to the Chief Joseph Rally in June, if it happens, instead of my oilhead. 

Thanks for the advice gentlemen.

When replacing the oil filter always do two inspections: poke the pressure relief ball in the bottom of the canister well. about 3:00 IIRC. make sure the ball is nice and springy and not cocked. then look at the base of the oil standpipe for an old o-ring that fell off a previous filter. this will effectively shorten the standpipe leading to crushing of subsequent o-rings.

when replacing the oil pan the oil filter cover must be off. make sure bolt does not go through and mash canister. on the /5 the canister may be deep enough it is a non-issue.

the rotor needs a special tool to remove. the stator comes off with your fingers and a bit of wiggling.

going into the timing chest is not a big deal. have the pan off, take lots of pics of the wiring, a bit of heat around the crankshaft, etc. ensure ALL the new gaskets are in place. observe the old ones.