Topic: Applying sealant to pucks... with shims!

[evanphi]

Got my cam towers from edwardmorris... friday night is when they go in!

I had some 0.030" shims cut for my pucks, since I was only getting 0.010" compression based on the depth of the recess, and thickness of aftermarket pucks.

with the crop of too-thin head seals we keep seeing, here is a way you can check the ones you got in your gasket kit (or elsewhere, like PartsNmore or CB750Supply, etc.).

First, check the step depth of the head hole. Then, check the thickness of your seal. You need at LEAST .030" compression, .040" is better. The too-thin ones are only about .005" thicker, which won't seal when the head heats up and the hole becomes deeper.

SO... when I put Permatex No. 2 around my pucks... Should I:

A) permatex, shim, puck, then wipe up excess?
B ) shim, permatex, puck, wipe excess?
C) shim, puck, permatex, wipe?

BrandEn's thread suggests put it in the recesses first, but HondaMan's book it looks like it is being wiped around the pucks once they are in.

[PeWe]

"D) permatex, shim, permatex, puck, then wipe up excess"  make me to feel better.
I'll look for thicker pucks or finding shims for next CB750 project

[evanphi]

"D) permatex, shim, permatex, puck, then wipe up excess"  make me to feel better.
I'll look for thicker pucks or finding shims for next CB750 project

my shims were made with 0.75mm (0.030") gasket material, and a 1" circle punch, made from some 1" OD steel tube.

[koendd]

"D) permatex, shim, permatex, puck, then wipe up excess"  make me to feel better.
I'll look for thicker pucks or finding shims for next CB750 project

that's how I would do it too!

[martin_uk]

Havnt come across problem with thin pucks as always used genuine.

However, I did use a tiny amount of  silicon sealant between the puck sealing edge and the head.

To my knowledge this is the important area to seal to prevent oil leaking into external area of  head casting.

If a shim was used I would fit between puck and cam carrier, which does not need to be sealed but just exert pressure on puck against head.

I have only done 2 of these engines so happy to be corrected.

[PeWe]

Havnt come across problem with thin pucks as always used genuine.

However, I did use a tiny amount of  silicon sealant between the puck sealing edge and the head.

To my knowledge this is the important area to seal to prevent oil leaking into external area of  head casting.

If a shim was used I would fit between puck and cam carrier, which does not need to be sealed but just exert pressure on puck against head.

I have only done 2 of these engines so happy to be corrected.

Good idea too.

I have pucks from both CycleX and Yamiya750.com The latter were not that thick either. I used rather thick layer of not hardening sealer under the pucks. There is risk that too much not hardening sealer is pressed under the cam towers and hit the oil holes. I saw some sealer floods on my head under the towers. But Ok for the oil.
Engine Silicone on the alu surfaces that allows to harden before the puck going in to ensure pressure on the seal.

The cam studs are another leak risk. Check if alu has a radius up to the studs, this indicate threads going bad. Helicoil or time sert will fix that. Red Loctite heat resistant (272) that lock the thread inserts, white permatex that seal the stud threads. I used Permatex 80632. There is one that resist even hotter, 59235.

I got recently a flood of oil leak that made me think about valve cover off with cam etc etc an reseal studs, rubber pucks. It was one bolt on the breather cover that I had forgot to tighten, the front one.

Frame mod make it simple to do this job without lifting the bike from the engine.

[evanphi]

Yep I did Frank's frame kit. So no worries if a leak re-appears.

Your comment about the material coming up... that's why I thought (permatex, shim, puck, wipe) was the best option. Less likely for any to be on top, and allows it to get down around past the shim to come down through the hole.

[shinyribs]

Use threebond or something similar. Silicone wreaks havoc on delicate oiling systems.

[evanphi]

I'm using Permatex Form-A-Gasket 2... No silicone on the inside!