R75/5 rocker bushings

[ebeeby]

The right, exhaust side rocker arm bushing had gone over 6 thousanths out of round - you can easily feel the lip. The shaft has some scoring. Symptom was noise and I could never get the assembly tight enough to reduce side wiggle of the arm.
Motor has 40,000 miles.
I replaced both the arm bushing and the spacer bushing and everything bolted up nicely, noise is gone. I have a new shaft on order as it is 2 thousandths out of round.
I did the intake side "while I was in there"

Here's the question:

The PO replaced base gaskets on this motor and had the jugs off. Looks like he used an orangey-brown gasket sealer on the head gaskets. Is it possible to clog the flow of oil down the top cylinder studs to the rocker assemblies by gooping up the opening on the gasket installation?

[dlearl476]

Here's the question:
Is it possible to clog the flow of oil down the top cylinder studs to the rocker assemblies by gooping up the opening on the gasket installation?

Is it possible? Dang near anything is possible. Is it PROBABLE? Only you can tell by looking at the aftermath. AFAIK, neither base gasket or head gasket need anything but a film of oil on them to seal under ideal conditons.

[AntonLargiader]

Is it possible to clog the flow of oil down the top cylinder studs to the rocker assemblies by gooping up the opening on the gasket installation?
Absolutely, and it happens often. You need a VERY light film of sealant on the base surfaces, and then you need to verify oil flow after the top end is back together. Later models got O-rings up there which help keep the oil in and the sealant out. You can also just use Hylomar; it's safer but isn't as effective. You'll get a bit of oil staining on the case (just clean it off every now and then).

Head gaskets go on dry.

[flash412]

I always run freshly-assembled airheads with the valve covers off until I SEE the oil running off all of the rockers. It doesn't take long. It doesn't make nearly the mess that insufficient oiling makes.

[FrankT]

Yes, it's possible as others have said. It's also possible the PO reinstalled the rocker arm assembly incorrectly. The oil to the rocker arms is fed through the upper cylinder through bolts and there is a definite top and bottom orientation to the shafts for proper oil feed. That being said, the /5 rocker assemblies seem to be prone to premature wear. Seems like a lubrication problem. I went through two sets of shafts and bushings before I replaced with the later style assembly (/6 and later) having the needle bearing rocker arms, no probelm since, that was in 1985.

[ebeeby]

Frank -
Just curious if you remember the mileage at which you replaced the shafts and bushings. Also, were the shafts bad both times?

I disassembled the rocker sets for the express purpose of ensuring that the shafts were right side up for just the reasons you state. They were. But I had a clear failure of the exhaust assembly, right side, with the bushing out of round more than 7.000ths and scoring to the shaft.

I have replaced the bushings on the right side (both rocker and spacer) and am waiting on more bushings for the left side (though they have not failed - they just have 40,000 miles on them) and a new shaft for the right side exhaust.

I plan too to take flash412's advice and run it on the lawn with the valve covers off to see what kind of flow I am getting. Clearly I am getting *something*, maybe even a normal flow, as the assemblies are always oil drenched and the valve covers have their noraml pool of oil to drop when I remove the covers.

Heck, it may just be it got dry at one point in the last 33 years and has been failing (failed) ever since.

[flash412]

I plan too to take flash412's advice and run it on the lawn with the valve covers off...I never said to run it on the lawn. Run it in the driveway over a couple of stacks of sheets of old newspaper or maybe a couple of old t-shirts. Motor oil will kill your lawn.

[FrankT]

Frank -
Just curious if you remember the mileage at which you replaced the shafts and bushings. Also, were the shafts bad both times?

I seem to recall that it was at about 50k. The shafts and bushings were scored both times. This essentially increases valve adjustment and affects performance, not to mention is noisy. My recollection is that there was more wear on the shafts than the rocker arms but that's kinda academic. Although it is a similar arrangement to what was used on the /2's, there appears to be an inherent problem with the /5 application. My opinion is it's lubrication as I mentioned before. The parts will still wear even with the shafts in the proper orientation. The later style hardware also quieted down the valve noise by maintaining closer valve clearance and eliminating the spacer. Don't have any idea what the later style parts would cost today, back then it was about $150 for all four, but that was also around the last time the $ was worth something.

[pmdave]

While I was bringing the 1971 R75 "toaster" back to life, I noticed the exhaust rocker bushings were worn, the intakes were still good. Since I had some needle bearing rockers lying around, I converted the exhausts to needle style, by having some bushings turned to match the square rocker blocks to the R75 heads. I left the intakes as bushings.

Seems to be working fine. Less clattering from the valve train, less variation in clearance control, and still the comforting ticking of the rockers at idle that let's me know the world is right.

pmdave

[GregFeeler]

I always run freshly-assembled airheads with the valve covers off until I SEE the oil running off all of the rockers. It doesn't take long. It doesn't make nearly the mess that insufficient oiling makes.

I do exactly the same thing. Well worth the clean up mess. :thumb

[rinty]

You guys are keen! But it's going to do more damage to your Idaho lawn than Ebeeby's sun-scorched Texas lawn, Greg.

We'll see you next week at the Stomp, and I'll have to buy you a beer to reward you for your extra effort.

Rinty

[GregFeeler]

You guys are keen! But it's going to do more damage to your Idaho lawn than Ebeeby's sun-scorched Texas lawn, Greg.

We'll see you next week at the Stomp, and I'll have to buy you a beer to reward you for your extra effort.

Rinty

I'll take your beer - but only if I can buy you one in return! :beer See you in a week.