The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Mike V on November 14, 2009, 04:03:45 PM
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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.
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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 .
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Let's try this again...Do'h
(https://bmwr65.org/smf/proxy.php?request=http%3A%2F%2Fi428.photobucket.com%2Falbums%2Fqq8%2Fgruntyman66%2Fx81R65Pushrods036small.jpg&hash=27a6eb5a8b459241f7f18eed9e9d910294837cdb)
(https://bmwr65.org/smf/proxy.php?request=http%3A%2F%2Fi428.photobucket.com%2Falbums%2Fqq8%2Fgruntyman66%2Fx81R65Pushrods037small.jpg&hash=39fc473fa699aa13e56adba218e5dea31ee6bd4b)
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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.
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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 .
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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.
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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
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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
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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.
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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.
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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.
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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
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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
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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.
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I have a limited supply of free push rods, courtesy of my crashed engine.
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Rob,
Very much appreciated. I'll be in touch if I decide to replace it. I don't "think" it's bad enough to jeopardize the strength or function.
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I saw that rubbing on my pushrod. It seemed to be the gasket. Only one way it should go and it was wrong on my bike. Ted Porter did the head work. Writing on the gasket faces out?
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OK Guys,
I found it! Look closely at the attached picture. You're looking at the right side cylinder - exhaust pushrod tube. Clearly you can see the abrasion marks where the pushrod has been contacting the ridge of the tube. Now I would have never brought this up in the first place if that score mark in the pushrod wasn't substantial. As I've mentioned before the best way I can describe it is as if a pipe cutting tool has taken a couple passive revolutions around it. Alignment issue? Is there really that much axial adjustment in the rocker tower? Maybe a rotary tool port job is in order? I hope this photo comes through...
(http://)
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So sorry guys...here's the photos of the pushrod tube...
(https://bmwr65.org/smf/proxy.php?request=http%3A%2F%2Fi428.photobucket.com%2Falbums%2Fqq8%2Fgruntyman66%2F81R65RestorationPushrodScoring002.jpg&hash=b3fc83799016614aa4b91cc852d379d5a8b8f92e)
(https://bmwr65.org/smf/proxy.php?request=http%3A%2F%2Fi428.photobucket.com%2Falbums%2Fqq8%2Fgruntyman66%2F81R65RestorationPushrodScoring003.jpg&hash=47a57229599a45481a27bd21ae8412abf871aa36)
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That does look like a culprit! Why it would rub there is an unknown to me - provided that the pushrod is straight.. maybe the tub itself is too long or slipped upwards? Maybe the pushrod angle doesn't match that of the tube/channel - how do the lifter/tappets appear - worn?
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nhmaf,
I didn't want you guys thinking I was crazy, or Chicken Little. By visual observation ...all looks good. Although its hard to determine the correct batter on the tube alignment by eye, but it has to follow the cylinder bore for the tube pressing! The pushrod seems straight with the use of a straight edge. I may try rolling it on the glass dinner table. The tube length at the end looks equal to the intake tube. Rocker tower didn't show anything out of the ordinary - hammer end looks good, etc., etc. ?????
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At least you know that the pushrod is rotating by design as it should (from the scoring around the rod's circumference), so the offset at the rocker arm end is probably OK.
Hmm [smiley=huh.gif]
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You might want to post this around to get lots of ideas.
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Rob,
I have an Airhead message (off-list) to Oak and Bum. I'll probably hear back from them tomorrow. Oak had shown some interest regarding the cause if I ever found it and I will probably post a message to the Airhead List after I communicate with him and get some opinions along with more concrete information. Kind of interesting - I'm not sure if this has ever come up before. I'm real anxious to hear what they say. Bum is having some computer problems of late and can't open photos. I'm glad I was finally able to flush it out of hiding - the heads and jugs are going out to Ted Porter this week for updated exhaust seats and I'll be sure to discuss it with him also. I'll be sure to keep the forum updated when more information is available. I appreciate you guys hanging in there with me.
Mike V. / San Diego
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I'm just happy you have seen the light of the mid-weight beemer.
I am on my 2nd engine transplant, and both times I never considered anything but another 650 to replace the blown-up or crashed engines.
I have had a 1000cc twin before, though, but it was shoved into a /2 frame and did sidecar duty - using the original ~'63 driveshaft and final end! Now later, with info gleaned from the internet, I discovered I was pretty lucky I didn't wreck the final drive.
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Rob,
Thanks. Heard back from Oak, he's quite pleased we found this. He's going to publish the information in "Airmail". I can attach his exerpt if anyone is interested later tonight when I get home from work. "Work", always gets in the way of shop time!
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I didnt have any markings on mine when i rebuilt it at 30k miles,Rebuilt only because it had been stood for 10 years!....haveing fitted new gaskets it will be intresting to check them on the next rebuild (if i live that long).
Lou
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I wanted to share Oak's response and fix. Thanks guys...
Mike, Bingo: Good work Sherlock. Looks like at least one of the culprits of pushrod scoring has been clearly identified. I have long suspected what your photo shows was the true cause. It eluded prior discovery because it wasn't that well defined as is shown in your photograph with the super clean sterilized cylinder.
What is happening is related to my stated cause #4 as given in my prior response. As the rocker operates the pushrod actually moves up and down slightly and ever so little left to right. The allowable tolerances in design in some instances obviously weren't quite enough to avoid the pushrod "crossing into enemy territory " as I had opined..
There is no provision to adjust the rockers to fix that problem for 1976 and later models.. What I can suggest if the engine is still apart, is to take a dreml grinder and using a high suction shop vacuum, carefully trim away just the interfering edge of the top of the pushrod tube where the pushrod is striking. You won't need to remove very much material. I strongly suggest trimming the pushrod tube with the jug off the machine then wash the jug off of its grit when done to make sure none of the abrasive dust or metal gets into the engine. Taking a bit of the pushrod tube away won't cause any integrity or leak problems and should provide enough clearance to do the job and avoid any future rubbing. If there was a noise produced which you have suggested to have occurred, that should go away also. There is no need to replace the pushrod so long as it is straight and otherwise undamaged. Just polish the scuffed area a little to smooth out any score marks.
The pushrod scuffing issue has been a long standing question and now we have for sure one certain answer to the mystery. Persistence pays off. .Thanks for your diligent hunting. Those things I have scarce time to dig into thus your help was most welcome............Oak
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Oak is so cool!
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Rob,
I can't begin to tell you! Love the guy! He's always there with a solid practical accurate resolution. And never afraid to put me in my place when I wander off base. What an incerdible resource for all of us.
Mike V. / Grasshopper
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Here's some photoos after the trimming of the tubes with a rotary tool.
(http://)