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Leaking Valve Cover

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Steven Shockley
(@14922)
Posts: 24
Eminent Member
Topic starter
 

My ‘83 R100RS has developed a slight leak from the left valve cover. Before I try anything else, I was going to try tightening it down. Is there a specific torque it should be tightened to?

 
Posted : 10/19/2023 13:24
James Strickland
(@8053)
Posts: 411
Reputable Member
 

It would be prudent to make sure all the nuts are tight. There is probably a torque spec, but I don't know what it would be. A common occurrence is for the stud for the cap nut in the center to be fatigued in the head and unable to remain tight.

This post was modified 4 months ago by James Strickland

former Airmarshal, IL.

 
Posted : 10/20/2023 04:37
Steven Rankin
(@14724)
Posts: 143
Estimable Member
 

Not knowing the condition of the bike, I will ask what condition are the gaskets in?

James makes a good point, as far as I know there is no torque spec, other than snug, LOL, but not too snug.

The center stud is known to pull out and damage threads if over tightened.  Also, if the threads are damaged, oil will migrate and leak as well.  Damaged threads can me fixed.

Not saying you used gorilla torque yourself.  But if you bought the bike used, there could be previous owner's disease in the threads.

If you are the original owner, first just check to assure things are snug.  If not, next valve adjustment, it might not hurt to change gaskets.  St.

Beware! I do not suffer fools gladly! St.

 
Posted : 10/20/2023 05:02
David Elkow
(@4949)
Posts: 278
Reputable Member
 

I found one value published for the center nut at 10.5 ftlb.  That seems like A LOT, to me. I used to over- tighten mine until I finally pulled the threads out of the heads. Reworked with steel thread inserts. Now, I go with “firmly snug”.  That goes for the two 10mm nuts, as well. If using silicone gaskets, gotta back off to just “snug, plus a smidge”.

 
Posted : 10/20/2023 06:55
Richard Whatley
(@wobbly)
Posts: 2498
Member
 

• Stop ! There most certainly are torque specs on the 2 nuts and center stud. 14 ft-lbs (max) on the center; 4 ft-lbs on the two 6mm. If you don't follow these specs, then you can and will pull the stud out of the cyl head at the center position. Proof again that "more is not better". The problem is that the alloy for the cylinder head is VERY soft.

• Whenever I had a leak at the rocker cover, it was always due to cheap, imposter gaskets. Rocker covers are the one location that you MUST use official BMW gaskets. Before fitting a new gasket, the head and cover must be: 1) clean of all debris and prior gasket and sealant material, and 2) both surfaces must be smooth and flat.

I find that official BMW rocker cover gaskets can be reused almost indefinitely, as long as the covers are refitted to the same cyl head in the same position/direction. Reuse will more than make up for any extra expense incurred in buying the BMW gasket.

 

Related Details

• Rocker covers are prone to leak because there is always ~50cc of engine oil "trapped" in the rocker cover, waiting to flow down the push rod tubes and return to the sump. There's no way around these "puddles". 

• If you take the center stud to the prescribed torque and feel the stud "give way" or fail to come up to torque, then your stud was previously over-torqued and the threaded hole in the cyl head is stripped. The quickest good fix is to remove the stud. Find a metric hex nut that fits the end of the stud fitted to the cyl head. Use a bench grinder to form 2 opposing sides of the nut into a shape that will slip into the air void in the cyl head, which is directly below the spark plug. Insert the nut into the void and reinsert the stud slightly deeper into the cyl head so that the stud engages the steel hex nut. This steel-on-steel is a permanent fix that will never pull loose, and for all intents the nut is hidden by the plug cap. 

 

Hope this helps.

This post was modified 4 months ago 2 times by Richard Whatley

[color=blue]Don't hide 'em, Ride 'em !!
#15150[/color]

 
Posted : 10/20/2023 09:36
Steven Shockley
(@14922)
Posts: 24
Eminent Member
Topic starter
 

Thanks for all the input. The bike is recently back from a major servicing at a reputable shop. I need to check my receipt to see if the gasket was replaced, but I expect it was. I’m hopeful that tightening it to the required specs will take care of the problem.

 
Posted : 10/20/2023 09:47
Richard Whatley
(@wobbly)
Posts: 2498
Member
 

Posted by: @14922

I need to check my receipt to see if the gasket was replaced, but I expect it was. I’m hopeful that tightening it to the required specs will take care of the problem.

• The real BMW gaskets are jet black on the sealing surface, and dark gray on the edge. Most of the imposter gaskets are sandy tan.

• Adding more and more torque to the central stud is (I imagine) how the cyl heads get stripped out to begin with.

 

[color=blue]Don't hide 'em, Ride 'em !!
#15150[/color]

 
Posted : 10/22/2023 04:56
Steven Rankin
(@14724)
Posts: 143
Estimable Member
 

An old BMW mechanic now passed made a comment years ago about over tightening things.  "if you look at the average 10mm wrench or 13mm wrench they are a certain length and allow only so much leverage, the key is to be comfortable with how tight you make things, don't strain too hard."

Thank you Richard for supplying the official torque specs. 

I will mention the "official BMW" gaskets my local airhead shop has been buying the past couple of  years tend to leak upon installation unless some kind of light sealant is used.  

In my case, I use a light spray of gasket adhesive, not a gasket sealer.  This is just enough to prevent leaks until the new gasket ages a bit.   The added benefit of adhesive is the gasket will either stay on the cover or the head when the cover is removed. St.

Not for nothing, I know a few fellows who use the aftermarket silicone gaskets and have NO problems at all.

This post was modified 4 months ago by Steven Rankin

Beware! I do not suffer fools gladly! St.

 
Posted : 10/23/2023 04:57
Steven Rankin
(@14724)
Posts: 143
Estimable Member
 

The other method of repairing the stripped center stud is to properly install a heli coil.   I have done two and with good results.  St.

Beware! I do not suffer fools gladly! St.

 
Posted : 10/23/2023 05:08
David Elkow
(@4949)
Posts: 278
Reputable Member
 

Probably too late to be of any help here, but - I contended with leak prone valve covers for several seasons. Finally resorted to silicone gaskets, which seal very well, but are a PIA to deal with in other respects. FINALLY, I took the time to flatten the valve cover sealing surface. I removed the studs, and flat sanded the covers with 320 grit, then 400, then 600 wet sand.  I can say with certainty they were not flat when I started, but dead flat when I finished.  Went back to the standard BMW gasket, properly torqued, and zero drips!  Yeah!

 
Posted : 11/11/2023 11:57

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