Oil inside and at the base of the front cover

bakerlonglegs

bakerlonglegs

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Hello, please may I ask for the collective’s advice?

My 81 R100 has oil inside the front cover and at the bottom of the timing case. Is this normal (I’m guessing not) and if dodgy what could be causing it? (The pushrod tube seals are also leaking but I’m assuming that as they are further back they can’t be the culprit.)

Many thanks


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There's a large 'o' ring around the nose of the 'bean can' ignition. That gets flattened. Mine's got an oil mist in the same area. I think you probably need the exact size, either from someone who knows, or from Motorworks/BMW. I tried another size I had knocking about, but it was too thick, so put the original back on for now. Remove the 'bean can' and you'll see the 'o' ring.
 
I have the same on mine and you've just reminded me! I could have ordered a new seal for the beancan along with my sh petrol tap!

Saying that, it's not much of a leak so it'll be ok for a while yet. I reckon yours will too!
 
Thank you very much for the info - thank gawd for that! I was dreading someone telling me it was some hard to reach seal in the guts of the engine, take it to bits all over the bench job… :comfort
 
mikeyboy said:
When was the last time the ignition timing was checked?
The bean can is fully advanced.
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Good point, don’t know, not by me yet. I’m no airhead expert, by a long way, but even I can tell it’s not running right so I’m going to go right back and check everything.
 
bakerlonglegs said:
Good point, don’t know, not by me yet. I’m no airhead expert, by a long way, but even I can tell it’s not running right so I’m going to go right back and check everything.
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If it’s running and not pinking with the bean can in that position I’d suggest a worn timing chain.
As you stated earlier that the the pushrod tube rubbers are leaking I guess it’s probably time for a bit of TLC.
 
Thanks Mikey, I’ll look at that. It certainly does need some TLC - there’s a lot of oil getting into the airbox as well so I think I have a busy winter ahead :D . However I like working on it so no grumbles.
 
Investigations continue! It’s my first time inspecting an engine so all abuse and piss taking welcome and expected….

First up, as suggested above, the bean can seal is indeed goosed. Timing chain kit on its way, need to order the extractor bolt tool for the rotor.

In other engine TLC news….. After setting each piston to compression TDC, removed both cylinders and took the pistons out. The pushrod tubes are skanky and the seals look done and are rock hard, so they’re getting replaced. Will get new circlips too for the piston pins, plus cylinder head gaskets, cylinder base o rings and the two stud o rings at the top. The piston pins seem smooth with no lips but I’ll see if there are any check dims in Clymer.

Prior to disassembly I checked valve clearances (which were pretty close), then warmed the engine and checked the compression and it’s just less than 110 on both cylinders which Clymer says is low. The cylinder walls look OK to my inexperienced eye, no lips or uneven wear and I can still see the spiral honing (right spelling/term?) marks. In my investigations I’m going to check ring gaps next but other suggestions are welcome. The top of both pistons and cylinder heads are thick with black deposits.

While it’s in bits I’m also going to check the cam followers. Is it worth checking the con rod bearings too? I assume that means new con rod bolts and I’ll probably need the special tool for the bolt heads….

I’ve also disassembled the carbs, all o rings and seals need replacing. The carbs will get ultrasonically cleaned as they picked up a lot of oily deposits (the airbox was oily AF, so much so it had run down the back of the gearbox). The spark plugs were also pretty black. All-n-all lots to do.

We continue….

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There are engine pros on here but as a layman I would say oil on the pistons, on the plugs, in the carbs, in the airbox and combined with low compression is all consistent with worn piston rings.

Worn rings cause low compression and allow oil blow by.

You could pop the rings off the pistons and place them in the bore and measure the gap.

That may give you some indication of their condition
 
Thank you all very much for all the advice :beerjug:. Will check all that.

I had not heard the terms ring lands or valve seat pocketing before, just had a read about them. I now see what you mean about the exhaust valve. Will check the ring lands but I fear sorting the valve seats might be beyond my meagre skills but I’ll have a read up to see if it’s something I could learn to do.

Thank you again!
 
bakerlonglegs said:
Thank you all very much for all the advice :beerjug:. Will check all that.

I had not heard the terms ring lands or valve seat pocketing before, just had a read about them. I now see what you mean about the exhaust valve. Will check the ring lands but I fear sorting the valve seats might be beyond my meagre skills but I’ll have a read up to see if it’s something I could learn to do.

Thank you again!
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We can fit new hardended valve seats and guides etc
Happy to take a look at the bores and pistons if you want to pop over
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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