Topic: O-Rings Instead of Oil Pucks

[reddyvv]

No offense intended, but if you can buy all six of them OEM Honda for $14.34 why bother testing alternatives? That's what I paid at www.hondabike.com recently.

[Don R]

Well, they are a common point of leakage and trying an alternative sometimes works, or not. There have been discussions about the new ones being thinner and/or not as large dia. and not sealing well either. Your mileage may vary
 I used the non hardening permatex on mine. I had another problem later and removed the head, those babies were welded in place, it took my pocket knife to get under an edge to pull them out.

[bert96]

I used 2mm Heavy Duty High Temp Silicone sheet, and punched 1" pucks. No leaks there!!!

Where did you bought your sheet?

Bert

[74750k4]

McMaster-Carr

http://www.mcmaster.com/#standard-rubber-sheets/=nqd5v8

[Dave Voss]

Well, they are a common point of leakage and trying an alternative sometimes works, or not. There have been discussions about the new ones being thinner and/or not as large dia. and not sealing well either.

I've read the same thing, and combined with hit-and-miss availability at reasonable prices, I figured I would give the o-rings a try, especially since it could be done with little expense and effort.  At present, my oil leak has returned, and seems to be worse than it was before, so either another source of leaking has become a problem, or the o-rings that I installed have shifted out of position.  I'm planning to investigate this week, and I'll post my findings regarding the o-rings, be it good or bad.

[madmtnmotors]

While you're in there, keep a couple other things in mind:

1) The cam bearing caps use a threaded stud on one side of the bearing cap. Did you remove these studs while it was apart? These are bottomless holes (i.e. exposed to atmosphere above the head) and thread sealer must be used when reinstalling these studs into the head or they will weep oil.

2) The other side of the bearing cap uses a bolt. Normally, these are not an issue because they are not "bored through" from the factory and will not leak. The only caveat here is that the cam tower bolt and the bearing bolt LOOK identical, except the cam tower bolt is a little bit longer. If you use a cam tower bolt in the place of the bearing cap bolt and torque on it until hard enough it can "punch through" the bottom. If you look closely at the cam tower, you will notice that the oil feed for the cam bearing passes through this bolt bore in the cam tower. These bolts have oil under pressure behind them! If the bottom of any these bolt holes have been "punched through" by the inadvertent use of a bolt that was too long, then this bolt hole will leak PROFUSELY, due to the fact that the bolt passes through the cam bearing oil feed passage. Try diagnosing that! Sealer on the threads of the affected bolt hole will stem the flow and eliminate the leak.

[Dave Voss]

Good tips Wilbur, thank you.  So far, my engine has only had the camshaft cover removed for inspection, head nut torque check, and subsequent puck/o-ring replacement, so I hope I can rule out any other oil leaks due to assembly issues, although it could be anyone's guess what may have happened during previous ownership.

[70CB750]

It was discussed here - with dimensions and pictures - that not all pucks are created equal.  From what I remember, the CycleX pucks came on top of the comparison.  The other set was generic ebay or such???

[bjbuchanan]

bj ,  I'm with you. And I'm looking at a ragtop '64 this week. I'm confident I can engineer out the 'danger'.  Maybe I'll get a pinto next

my 65 I sold away

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I saw the thread the other day. Cyclex pucks were, when measured the a caliper, just slightly thicker and a tick wider without being an issue when compared to an OEM puck. The thread has pics with measurements too

[Dave Voss]

Okay, so today I removed the camshaft cover to inspect the o-rings that I installed in lieu of the factory oil pucks as mentioned at the beginning of this thread.  The engine began leaking oil from somewhere in the top end shortly after installing them, and I've suspected that perhaps the o-rings shifted out of position.  After removing the camshaft cover, I observed that the o-rings remained in position as I had hoped, and they were all in good shape.

Of the six that I installed, only the outer two sealed well enough to prevent oil from getting down onto the head nut cavities, as those two were completely dry.  The four cavities grouped at the center of the engine were all very wet with oil, in spite of the o-rings looking the same, and I thought this was an odd pattern to simply be a coincidence.

I decided to inspect the under side of the camshaft cover, and I noticed something that I had missed before.  The outer two locations that use the oil pucks are dead end cavities in the casting the of camshaft cover, but the four locations at the center have plugs that cover the inner ends of the valve rocker shafts.  Apparantly, these plugs don't actually seal, but rather allow some oil to pass around them.  My CB550 is a '78 model year, and I know there are early and late variants of the camshaft covers, so I don't if these plugs are specific to the later covers, or if all of them have a similar design.

In hindsight, this explains the small amount of oil that is normally found pooled on top of the those center four pucks, as it drips down from above at the ends of the valve rocker shafts.  So, replacing the oil pucks with o-rings was kind of a sucessful failure, in that the o-rings did effectively seal the camshaft cover to the cylinder head, but the hollow center created another significant oil leak from the ends of the valve rocker shafts past the mating surface between the camshaft cover and the cylinder head, straight to the exterior.

To recap, using an o-ring on the outer two positions works great, but the inner four positions need to use an oil puck.  I retained the oil pucks that I removed a few months ago, and reinstalled them with a bead of high temp RTV to help seal them, tomorrow I will test ride to see if the top end oil leaks are finally sealed.