Rocker cover leaks.

[Tony Smith]

I reset the head bolt tension and did my tappets last weekend and my rocker covers are leaking again.

The leaks are due to the contact surface deforming and the last time I did this I reset the head tension to 23ftlbs which left the mating surface flat enough to seal, but I can see a compression leak developing so leaving the tensions that low is not an available  long term strategy.

And yes, before anyone asks, my torque wrench is within spec - tested using a test rig specifically for testing torque wrenches.

My series of questions start with - Does anyone else suffer from chronic leaking rocker covers?


If you have chronic rocker cover leaks are your heads 79/80 or 81 -> ?


The reason I ask is that my heads started life as small valve heads, but have had the bigger valves fitted.


I also think I can answer my own question as to why they leak - my heads at some time in the past were extensively ported - I suspect that there is simply not enough metal left in them to maintain shape under normal head tension.


For the time being I have simply put two gaskets on each side and that has stopped the leaking.

[Warbucks]

Just a thought if I may. There's an American guy named Chris Harris on YouTube. He's a guru on boxers and he does lots of movies about fixing them. I'm not sure how you could contact him. Perhaps you might consider signing up at YouTube and see if you can get him there. I'll bet he knows what's going on.

[D Mann]

I remember Snowbum had a write up that included sanding the rocker covers, on a flat surface, to stop leaking so you are probably not the only one who has had this problem.

[Barry]

My series of questions start with - Does anyone else suffer from chronic leaking rocker covers?

Never had leaks, even if the nuts are only just beyond finger tight but I've always chickened out at 23 ftlbs and never torqued above that value.  

[marcmax]

I used to have small leaks that would come and go on their own. Replaced the gaskets with silicone gaskets and haven't leaked a drop in 4 years of re-using the same gaskets after adjusting valves.  

http://www.realgaskets.com/files/motorcycle.htm

[Bob_Roller]

I had the heads ' overhauled ', in '98, I got a call from the shop saying that the surface on the head where the rocker cover mates to, is not true .

They said it is a common problem with airheads, had the surfaces trued up and no issues .

A common ' fix', is two paper gaskets, or a rubber gasket .

Have not had to do this, so I'm not sure if it works or not .

[montmil]

I used to have small leaks that would come and go on their own. Replaced the gaskets with silicone gaskets and haven't leaked a drop in 4 years of re-using the same gaskets after adjusting valves.  

http://www.realgaskets.com/files/motorcycle.htm

Not too many moons ago, on my'81 R65, I replaced the push rod tube grommets, new rings and swapped in a pair of heads I had sourced several years ago "just in case". Had the new/old heads checked to confirm they were up to spec.
After reassembling everything and doing some proper break-in miles, the rocker covers were dripping oil.

I did two things to correct the dribbles:

1) Double-nutted the valve cover studs and removed them. Used my granite surface plate to true up the covers -using a figure-8 sanding action and WD40 as an assist. A machinist's straight edge and feeler gauges confirmed dead flat and true surfaces.

2) Installed black silicone gaskets from the source marcmax mentioned. Now dry as old bones.

[Tony Smith]

.

A common ' fix', is two paper gaskets, or a rubber gasket .

Have not had to do this, so I'm not sure if it works or not .

I WAS using silicone gaskets, I am now using 2 paper gaskets per side.

The covers are true.
When there is no bolt tension, the mating surface of the heads is true.


The problem is my heads, they have simply had too much metal removed when they were ported and now have the distortion resistance of cheddar cheese - apparently my problem is well known to people who have played with the ports on the bigger BMW heads. The people I asked had never heard of an R65 head becoming plastic because nobody had ever bothered porting them.

The story behind my heads was that I bought them as a pair of small valve heads from 'Boxerman" in England. He described them thusly:-

"I have had them for a very long time, I don't remember why or how I got them so I don't know what it wrong with them - use with caution.

"When they arrived they were HEAVILY encrusted in dirt, rodent droppings and grease - I gave them to my machine shop of choice and his initial comment was "I'll put them in the washer for a couple of weeks and then have a look."


The first "surprise" was that the small valve heads (by casting number) had big valves fitted. The second surprise was that one of the guides was loose, which caused me to discover the rather large difference in price between a non-OEM standard guide and a genuine O/S guide.

And the third surprise was when I picked them up and the machinist commented on the fact that sometime in the past someone had spent a lot of money with someone who owned a flow bench and knew how to use it.

[Bob_Roller]

Doesn't look like you have any real options , the heads are ' soft ' from too much metal removed .

If the heads distort to the point where you tighten the rocker covers, double paper gaskets, or rubber gaskets and it still leaks, looks like replacement heads to me .

[mrclubike]

I would look at them and see if their  is a way to add more bolts and or studs to hold the covers  on.
 
I wonder if you could use some JB weld or ultra silicone gasket maker  on the cover mating surface and put grease or wax paper on the head side and bolt them up when the sealer  starts to set,
After it  sets up  separate it and install a gasket.
 
Doesn't sound like you have anything to  lose

[Tony Smith]

For the present two paper gaskets per side and no leaks.

I think i will simply accelerate my program to buy a usable RHS head/pot/piston and revert the thing to bog stock standard. I have neither the time or interest in playing with carbs, cams and exhausts to try and get some advantage from the ported heads.

[Luca]

If your machinist has or could make a torque plate, then why not bolt the head to that, stick it on a mill, and skim it flat with the torque applied.

[Tony Smith]

If your machinist has or could make a torque plate, then why not bolt the head to that, stick it on a mill, and skim it flat with the torque applied.

Yes I agree, the idea did occur - I'd rather spend the money on a bog stock RHS cylinder and head.

Was a time I was heavily into modifying engines. The older I get the more I believe that "stock is best".