Topic: O-Rings Instead of Oil Pucks

[Dave Voss]

So, several weeks ago I had to stop riding my CB550K due to significant top end oil leaks (which appeared to be coming from the head gasket area) that I didn't have the time to fully diagnose or repair.  At that time, I received some great tips from folks here that the major source of the leak might not actually be the head gasket, but rather the oil pucks under the valve cover that seal the access holes for the cylinder head securing nuts.

Well, today I decided to remove the valve cover to inspect those oil pucks, and they did indeed look like they were flattened and not sealing very well.  After inspecting the underside of the valve cover, it appears that the oil pucks could be o-rings instead, as there aren't any passages, etc. that really need to be sealed, just the surface between the cylinder head and the valve cover.  I'm fortunate to live three blocks from a local hardware store that carries a huge assortment of o-rings, so I took an oil puck there to match, and found a size that fit very well as a replacement.

I installed the (6) o-rings in place of the oil pucks this afternoon, reset the valve adjustments, ran the engine for a while, and took a test ride.  Upon returning home, the majority of the top end oil leak seems to be gone.  Has anyone else tried this?  So far, it looks like a promising alternate-part repair.

[Don R]

It was discussed recently but you may be the pioneer. Best of luck, I might give it a go too.

[acollin]

Never having replaced pucks or Orings in one of these bikes-- but will need to shortly as my 1972 cb 750 has that telltale weep--- is there an advantage to an Oring as opposed to a new puck.

3 blocks away from a repair is always good news , but are there other benefits?

Good luck

[dave500]

that will work fine,the idea of the solid puck i think is to prevent debris build up over time at the underside of the cover reducing corrosion?which might eat its way through under a simple o ring,just get a wad punch and some rubber sheet and punch out your own soild pucks.

[matt mattison]

Sounds like a good idea with the o rings and cork . When I re installed my valve cover, I ran a small bead of Honda bond in the puck recess and put back the old pucks. That seemed to do the trick as well.

[brewsky]

I wonder if they will migrate to the inside under the clamping pressure as that direction would be un-restrained.

I have tried to use o-rings in place of flat washers in other applications which wouldn't work due to them squeezing out of place.

The cork idea might take care of that however.

[madmtnmotors]

I wonder if they will migrate to the inside under the clamping pressure as that direction would be un-restrained.

I have tried to use o-rings in place of flat washers in other applications which wouldn't work due to them squeezing out of place.

This was my first impression as well.

[crazypj]

Even if they are not leaking I've found  little oil pool in the middle of 'pucks' so there must be some leakage?
 I'm still thinking of making some stepped plugs to support 'O' rings though because I'm fed up with the originals distorting and leaking

[Dave Voss]

Great input, thank you!  I agree that the use of a 'puck' in lieu of an o-ring provides added protection for the underside of the valve cover in those (6) recesses, especially if ridden on dirt roads or in wet weather, but since I don't do either of those, I think using o-rings should be alright.

I also noticed a small pool of oil in the center of each oil puck, and so they were leaking on the top side.  Mine were also slightly smaller in diameter than the counterbores that they sit in, so they were leaking around the sides as well.  It seems that these oil pucks must shrink over time, until they begin to leak.

I'm not sure how the clamping force of tightening the valve cover fasteners would cause the o-rings to collapse inward on themselves, as there is a farily wide step on the bottom of the counterbores that they sit in, but I suppose it might be possible.  If my oil leak returns, I'll investigate and let everyone know how the o-rings held up, and if they moved out of position.

[crazypj]

I think it's just because they live in a hot place, they do seem to hold up reasonably well considering it gets pretty hot in there 
Don't know if heat from exhaust could be  causing problem?
 Double skinned originals are probably 'cooler running' than single skin aftermarket?

[Don R]

A the risk of starting an oil discussion , the high mileage oils available have rubber softening ingredients, I wonder,

[Dimitri13]

For ultimate protection, why not tap the bores on the head, machine an aluminum plug with a recess for an o-ring, and use thread sealant on the threads?

[surveywaters]

The question of replacing the puck with an o-ring seems reasonable, I thought the same thing. Then realized that cb750supply.com sells the set of 6 pucks for $10 so why not just put in what came out?

[Dave Voss]

The question of replacing the puck with an o-ring seems reasonable, I thought the same thing. Then realized that cb750supply.com sells the set of 6 pucks for $10 so why not just put in what came out?

They were perpetually out of stock when I tried to order them, and other vendors want $3~4 each plus shipping, so that pushed me in the direction of pursuing the o-ring solution.

[surveywaters]

I see. I got mine from the stealership for $3 each, then saw them at cb750supply; they don't tell you things are out of stock until you checkout...  Good luck

[Bru-tom]

i bought a sheet of Vitton and Nitrile 1.5mm and 2mm thick respectively. i wonder if either of those could work?

[phil71]

I think the 'squish' combined with the heat, will likely cause the o-rings to quit sooner than the pucks.
YOu also don't say if you replaced the o rings at the sides between the head and the jugs. and the cam tower plugs. THey need a wider flatter o ring, but can leak like a bastard when  they go bad.

[bjbuchanan]

I think the 'squish' combined with the heat, will likely cause the o-rings to quit sooner than the pucks.
YOu also don't say if you replaced the o rings at the sides between the head and the jugs. and the cam tower plugs. THey need a wider flatter o ring, but can leak like a bastard when  they go bad.

The use of viton o-rings takes heat out of the equation. Viton is seriously tough stuff, impervious to damn near everything an engine can throw at it. I used them to seal the pushrod tubes on my corvair, literally didn't leak one drop of oil after a year

[phil71]

if Nader only knew about Viton

[bjbuchanan]

That clown fly got too much credit with the corvair stuff. Mercedes used the "unsafe" independent rear just like the early model corvair and nobody would ever think to say a German car could possibly be unsafe. Engine fires are a good one too, let's all use rubber fuel line on a 300 degree engine that is air cooled. Lazy people hurt a good car

Rant off

[bryanj]

Usr the "O" rings if you are into doing the same repair repeatedly mate!!!

[phil71]

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

[74750k4]

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

[CB750F2]

See topic 121248. Pat

[74750k4]

Originally I used double seal Viton o-rings and high temp siliconed them in place to the head. Let them cure. Assembled the cam towers with a small smear of silicone on them. Did a tear down of that about a week later. The o-rings shifted. One was almost off the shoulder of the head machined surface. i surmise the puck center helps to prevent shifting, and deformation.