81 R65 Top End Job - Pushrod Scoring

[Mike V]

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.

[suecanada]

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?

[Mike V]

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...

[Mike V]

So sorry guys...here's the photos of the pushrod tube...

[nhmaf]

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?

[Mike V]

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. ??

[nhmaf]

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]

[Rob Valdez 79 R65]

You might want to post this around to get lots of ideas.

[Mike V]

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

[Rob Valdez 79 R65]

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.

[Mike V]

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!

[Lucky_Lou]

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

[Mike V]

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

[Rob Valdez 79 R65]

Oak is so cool!

[Mike V]

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