Topic: Do I need to replace the pucks?

[denward17]

I took my engine out today (K8) to correct oil leaks and clean.

Does it look like I need just the pucks under the cam towers? 
 I also have a new neutral switch that will go in, I think it is leaking as well.

[Dunk]

Yes. Leak starting a few fins from the top of the head is the giveaway. Reach in to a spark plug cavity and feel the top... That's what the puck seals. If the outer ones are leaking it'll be oily in the ones you can reach.

[BenelliSEI]

When you lift the cam towers (to get to the pucks) carefully inspect the threaded holes the long bolts go down through. On my cb750K4 two of them are drilled and threaded right down through the fin to an open space in head. Seal the threads with a good sealant, or they will leak down through, just like a shrunken puck.

I always put a thin layer of HondaBond on the new pucks.

[Dunk]

Yes, Hondabond/Threebond/etc. on the sealing surfaces of the pucks and thread sealer on the cam tower stud threads. Cheap insurance.

[denward17]

Yes, Hondabond/Threebond/etc. on the sealing surfaces of the pucks and thread sealer on the cam tower stud threads. Cheap insurance.

Do I need to move the cam tower studs just to replace the pucks?

[BenelliSEI]

Yes, Hondabond/Threebond/etc. on the sealing surfaces of the pucks and thread sealer on the cam tower stud threads. Cheap insurance.

Do I need to move the cam tower studs just to replace the pucks?

Check closely from below. If they are threaded into blind holes, just make sure they are screwed in tight. If they are screwed right through an open hole, pull them out and seal those threads.

[denward17]

Yes, Hondabond/Threebond/etc. on the sealing surfaces of the pucks and thread sealer on the cam tower stud threads. Cheap insurance.

Do I need to move the cam tower studs just to replace the pucks?

Check closely from below. If they are threaded into blind holes, just make sure they are screwed in tight. If they are screwed right through an open hole, pull them out and seal those threads.

I don't plan on removing the head, can I see if they are screwed into an open hole without removing head?

[BenelliSEI]

You don’t need to remove the head. To get to the pucks, you will have to remove the camshaft and then the cam carrier. You pretty much strip the top of the head bare, and will be left with four studs that held the cam carriers down. I have a bare head sitting on my bench, with those four studs still poking out. I’ll post a picture tomorrow.

On some heads, the holes those studs (and the four holes left by the matching long bolts) are threaded into, go right down through the casting and out into the finned air space below. You can probably peer in there with a bright light and see the hole or the end of the stud. If you can see one, it’s very easy for hot oil to wick down the threads and drool out. Much the same thing that happens when the pucks shrink and start leaking. Turn the stud out, clean the threads with Brakleen (stud and the hole) and apply a good sealant, or even a few drops of blue loctite, when you reinsert the studs and tighten them down.

If none of them are poking through (very possible) ignore everything I’m suggesting!

[denward17]

OK, understand now, Thanks for the detailed response.

[BenelliSEI]

OK, understand now, Thanks for the detailed response.

Pleasure! I had this issue too. In the Project Shop Section, check out my way “1974 Rickman Honda” posts. Page 6 is all about a stud leak, and a non original part fitted. Who knows what you may find??

[MauiK3]

While the engine is out be sure the head gasket isn't leaking too.

[PeWe]

When cam and holders are off, retighten the head nuts.
20ft lbs no problems on stock studs. From inner to out.

If pucks are hard they need a replacement.
If OK, sealer before pucks will be good. 

I have used Hermetite Golden in the early 80's, then Blue Hylomar not as good, then Hondabond aka Threebond 1184, after that Permatex Aviation no 3 which is rather messy when it will flow around and make dirty.

Last times high temp 329*C black silicone under pucks.
 
I let it cure a little before tightening camholders. I have tightened a little to remove cam holders to see if any extra will overflow to the oil orifices. Clean overflowing sealer. The other sealers could overflow.

Not messy and stay put. No leakage yet.

I have even sealed a leaking RCS (Rubber (viton) Coated Steel) base gasket with the high temp silicone. Very, very thin layer on the gaskets both sides, outer sealing area that cure for a few hours before assembly.  (Got the tip from 2 shops near me)
For big bore sleeves.
Gasket not available here, Dynoman.
No risk for sealer overflow on the inner 2 cyl studs for oil transport to head when cured before assembly.

[denward17]

I have some Hondabond on order for the pucks, is that ok?

[BenelliSEI]

Hondabond is my favourite solution. Here’s the photo clearly showing the four cam block studs. The pencil point indicates one of the four opposing holes that take the long bolts for same. Check them all to see if any are drilled and tapped right through to the first air gap below. If they are (none on this early head) make sure you seal up those threads too. Good luck!

[denward17]

Hondabond is my favourite solution. Here’s the photo clearly showing the four cam block studs. The pencil point indicates one of the four opposing holes that take the long bolts for same. Check them all to see if any are drilled and tapped right through to the first air gap below. If they are (none on this early head) make sure you seal up those threads too. Good luck!

Picture is worth a thousand words 
Thanks

If the bolt holes are open, would oil primarily leak on the intake side?

[BenelliSEI]

Not really..... On my Rickman Oil was drooling out between #3 and #4 exhaust ports, at the front. It looked a lot like the concentrated mess in your first picture, between #1 and #2 exhaust ports. The engine leans forward, so it will come out the front. It’s most likely the #2 puck hole (from the left side, sitting on the bike), but check that stud for sure. You’ll know when you pop out that puck. You’ll look down below and see tons of muck in the air space below.

[ofreen]

I suggest re-torquing the head while you are in there.  I prefer to do it one at a time.  You will probably find when loosening, a nut will pop and be very loose.  Then when torquing down to the value, it will turn well past where it was.

[denward17]

Thanks Guys for the info and tips, will post pictures when I tear into it.  Waiting for parts to arrive...........

[BenelliSEI]

When I “retorque” anything, I don’t break it loose. Just pull to spec. If it doesn’t move, it’s tight.

[Stev-o]

BranDen did  nice write up on how to have a leak free engine...

http://forums.sohc4.net/index.php/topic,107040.0.html

[BenelliSEI]

BranDen did  nice write up on how to have a leak free engine...

http://forums.sohc4.net/index.php/topic,107040.0.html

Steve-0...... Just reread. EXCELLENT PIECE!

[denward17]

Yes, I have read that thread a couple of times and will reference again just before the work.

[MauiK3]

It's just me
These bikes are all old. If you don't know if it was ever taken apart you have old gaskets everywhere including the head gasket.
Just sayin'

[PeWe]

Hondabond is my favourite solution. Here’s the photo clearly showing the four cam block studs. The pencil point indicates one of the four opposing holes that take the long bolts for same. Check them all to see if any are drilled and tapped right through to the first air gap below. If they are (none on this early head) make sure you seal up those threads too. Good luck!

I have a head where a PO had repaired threads with helicoil and succeeded to drill thru those holes.

I removed the helicoils and plugged the bottoms where a hole went thru with JB Weld, tapped to fit Wurth big-sert thread inserts.
I plugged first with the JB Weld 2k clay, put screwdriver  between the fins to hold right under the hole, then pressed with a drill. Not much, enough to plug it. Or finger if reached via the rubber puck hole.

I added the good >24h hardening 2k JB Weld wich is thinner and much more durable to fill bottom a little.
Mount the thread insert locked with Loctite 272.
Be careful to not drill too deep for inserts. Bolts should not hit bottom too early either.

Agree about old gasket + o-ring another thing. Lots of work to pull engine.

[ofreen]

When I “retorque” anything, I don’t break it loose. Just pull to spec. If it doesn’t move, it’s tight.

Or it's stuck.  I had the engine out of my '75 750F twice over the years.  The first time the base gasket was weeping.  Re-torquing the nuts and bolts using the method I described solved that.  Still no weeping there at over 167,000 miles.