81 R65 Top End Job - Pushrod Scoring

[Mike V]

Anybody ever run across this situation before? Top End Job dissasembly went well today. Although, I found obvious scoring on the left intake pushrod and the right exhaust pushrod. Nothing obvious I could see inside the tubes or at edges. Yes the bike did make a clicking sound years ago when it was running last and I've had my eyes open for the cause. Pushrods seem to be straight and the only abrasive goove is in the right side exhaust pushrod. For reference I have the 0" end of the ruler at the outboard end of the pushrod or at the end that mates to the rocker arm. Hope the photos come through...

Any idea's - experience?

Mike V.

[Bob_Roller]

I noticed this, when I took the heads off for a top end about 11 years ago, my best guess, was that the push rod was rubbing on the head gasket .

I installed a copper head gasket, made sure there was no contact between the two afterwards .

No photos, when I posted .

[Mike V]

Let's try this again...Do'h

[Mike V]

Bob,

The rocker axial play was minimal before dissasembly...BUT I'm thinking this may be a classic case of pushrod alignment. I have an email to Oak and Bum.  I've read about this many times but never experienced it personally and the actual amount of adjustment is something I'm curious to find out about.

[Bob_Roller]

I had needle bearing failure on a couple of rocker arms, the metal flanged end broke out, and needles started working out, in the small gap in the rocker arm blocks, that go over the threaded studs .

I'm sure this is where mine came from, they were more like polished, rather than gouged .

I measured them with a micrometer, and the material removed was negligible .

The cylinder head gasket that I had, had excess gasket material in the pushrod area, and you could see where it had a bit of material removed .

[Mike V]

Bob,
Rocker assemblies are in good shape. Head gaskets were installed properly and I believe this to be the first time the motor has been dissasembled. Oak had an interesting reply and basically reported it could be multiple causes. I'm going to go back to the shop and do a closer inspection of the head gasket at the pushrod port to see if there's any abrasion marks. Other than that I'm pretty well stumped but from the replies I've received to this point it seems it's not a life threatening situation. Although I'm not comfortable with the deep scoring on the right pushrod...it bothers me a bit and it just shouldn't be, in my opinion. I'll focus my inspection on that side and report anything obvious.

[nhmaf]

I had heard that this can often be from rubbing on head gasket material
(metal edge lip), but I cannot say for sure that it what you have there.

Let us know if you find out anything further and any other suggestions from Oak.   I had also heard that something else can cause this, and I printed it out for future reference but I'll be d@mned if I cannot find that blasted printout now in my bike file folders... grr

[Mike V]

nhmaf, et.al.,
I've made a very maticulous and close inspection on everything and I can see nothing obvious. Inside the tube barrels, head, cylinder, and even the head gasket. The stock head gasket has no metal sheath in the bore, only bare gasket materialn and I can't see anything that would indicate abrasion of any kind. Really weird. I'm a little concerned with the resulting structural integrity of the pushrod but doubt it will be a problem.

Here's Oak's reply;

Hello Mike:

Good question re-the pushrod scoring. There have been numerous theories what caused it and nobody is certain including myself. Haven't been able to nail it down with 100% certainty. I suspect the following and you can take if from there.

1) It was done at the factory during manufacture of the pushrod, in the fixturing.

2) The pushrod was rubbing the head gasket punched out area--just grazing it.

3) The valve lash may have been too loose and the pushrod excessively rattling.

4) A slight design error by BMW engineers in permissible clearance of operation where production tolerances allowed crossing over into enemy territory.

In any instance it has not seemed to cause any serious problem. The two areas I would examine is the head gasket hole,making sure it is not too small, and keeping the valve lash proper--( not excessive)  In the 1976 and later models there is no provision to relocate the pushrod movement to avoid any rubbing. If all seems OK yet it rubs and can be proven, there isn't much you can do about it except skinny the pushrod a little in the troublesome area. What you can do is degrease the pushrod and get some machinists bluing dye and cover the pushrod in the scuffed area. If the problem is still prevalent, it will show up with some of the dye scuffed away. ( the next time it comes apart !! )

That's about all I can offer. Let me know if you pin down the cause. It would be very welcome news.

.............Oak

[Mike V]

Here's a photobucket link to today's work. Everything else looks  great (except the two pushrods).

http://s428.photobucket.com/albums/qq8/gruntyman66/81%20R650%20Restoration/Top%20End%20Job/

Mike V.

[Rob Valdez 79 R65]

Mike (and Bob), I didn't read all of your discussion, but I have seen them on my engines, and never gave it a 2nd thought.  

But that was before the internet and digital cameras!  [smiley=thumbup.gif]

But speaking purely as a layman, I don't think it is much to worry about.

[trolle]

I'd say the same as Rob, there is scoring on my pushrods, and I have tried to find the reason, but as it has no discernable effect I've decided to let it be.

BTW I think that Clymer's mentions the problem.

greetings from a temporarily sunny and relatively warm north where the radio speaker found it neccesary to inform us that the round shiny celestial body, we are seeing today, is called the sun.

[montmil]

Could be leftover evidence of engine work/mods/repairs by a previous owner? You and I both have '81 models and I sure as heck know I didn't get a virgin. [smiley=2cents.gif]

Monte

[montmil]

Check out Ted Porter's BeemerShop web site and his page of Common Mistakes, especially the link to Airhead Head Gasket.

This may explain why you don't see any evidence of the pushrod rubbing on anything.   Monte


http://www.beemershop.com/mistakes.php

[Mike V]

Monte,
The gaskets were checked during dissasembly and were installed correctly as I've mentioned. Even though it's a mystery as to the cause of the marks on the pushrods, most all of the information I've gathered from various sources discounts it as a problem. I'll keep an eye on their alignment during reassembly and where the marks measure in relationship to the head and cylinder. Everything else other than the right exhaust pushrod looks fine. It almost looks and feels as though someone started a revolution of a pipe cutter tool on it.

[Rob Valdez 79 R65]

I have a limited supply of free push rods, courtesy of my crashed engine.