Topic: brandEn's leak free top end thread = Tips, Tricks and Suggestion encouraged

[brandEn]

This is being done on my 1978 CB750 F3

The purpose of this thread is three fold.
One; to make sure I do everything right (for the third time)
Two; to help others that need help assembling a top end and to make sure its leak free.
Three; a place for some of our members to offer advice


Checklist of  materials needed:

1. Hylomar PL32, Threebond, Yamabond, Hondabond, or Gasgacinch (non hardening gasket dressing)
2. Permatex High Temp Thread Sealer
3. Red Loctite (high strength)
4. Base Gasket (Cometic is preferred)
5. Head Gasket (Cometic is preferred)
6. APE heavy duty cylinder studs
7. Cam cover gasket
8. new rubber cam tower puck aka "rubber nickles"
9. New o-rings. There are a few different sizes needed. I will do my best to document where they go.


Hylomar PL32



Permatex Thread Sealant



Red Loctite (for the APE studs)



Gaskets



Cam Tower Gaskets



FOR REFERENCE
1978 CB750 F3


Cylinder-Head Cover



Cylinder-Head



Cylinder



Crankcase

[brandEn]

So first things first. I AM NO EXPERT! Take my advice with a grain of salt and not as gospel. I am open to suggestions. I have open ears and mind so if you see a better way for me to do something please chime in!


Lets install some APE heavy duty cylinder studs. I have decided to use some suggestions from MReick. I am using his procedure to install these and NOT following the instructions provided by APE.


1. CLEAN YOUR HOLES OUT!!!
Make sure your threads into the engine case are clean! I used a M8 x 1.25 thread chaser, barrel brush, WD-40 and compressed air to clean everything up. Spray the threads with the WD-40 and then run the thread chaser (or bottoming tap if you prefer) through each hole. Then blow each hole out. Respray with WD-40 then push the barrel brush in the hole and then twist it anticlockwise out. Blow everything out with the air.

2. INSTALL YOUR STUDS!
This is where things get different from the APE directions. Apply the red Loctite to the long end of the cylinder studs and thread into the case. If you don't have a stud installer just use two M8 x 1.25 nuts and a washer between them to install the studs. APE recommends to install the studs with oil until they bottom out and then torque to 8 ft lbs. I just used red Loctite and installed the studs until they bottomed out and then lightly snugged up. If down the road you need to remove the studs just use heat.

                                         *** WARNING ***
When installing the two cylinder studs with the oil feed holes be sure not to plug the small oil feed holes with loctite. Apply the loctite with a toothpick, and very little of it. Once the two studs are installed blow compressed shop air in the oil gallery via the oil pressure sensor hole. Verify the holes are clear by the air that shoots out of the stud oil holes! Making sure the holes are not plugged is VERY VERY important.
_________________________________________________________


3. CYLINDER & HEAD MOCK UP
Without the gaskets installed and the pistons removed slide the cylinders over the studs and onto the engine case. MReick suggested to use a couple layers of paper towel between the head and jugs to compensate for the thickness of the gaskets. So I trimmed a shop paper towel doubled over and laid it between the surfaces. Now slide the head over the studs and install your cylinder stud washers and nuts. Mike made sure to tell me " don't tighten the nuts to tight" so I just snugged them up enough to put some pressure on everything.


4. THE CURE
Now just chill out and wait 24 hours for the loctite to cure and setup.


Now is a good time to remove the four cam tower studs on the head and install the Permatex Thread Sealant to the threads. The holes these are installed are open to atmosphere and can be a source for leaks if not sealed.


My head "chilling out"



Parts waiting to be installed!

[brandEn]

My cylinder studs have sat for 24 hours and the red Loctite is set up. I removed everything and took some pictures of where all the o-rings go and some stuff to look for.


Make sure your gasket surfaces are CLEAN and free from any damage. Now is the perfect toime to make sure your head and cylinder mating surfaces are not warped. I had my surfaces decked by Cycle X so I am good to go. I used a steel rule just to double check. I don't want to leave any stones unturned!


Bottom of the cylinders are flat!



Top of the cylinders are flat!



Bottom of the head is flat!



Top of the head is flat!



The manual is clear as mud and it took me a lot of head scratching and forum searches to come up with this info. The bastard child F2-F3 engines only use two oil feed/return and the K models use 4. Here is a picture of the bottom of my F3 cylinder showing where the oil feeds up, through the holes on the right.





I had Cycle X install bronze bushings on the unused port that is usually exposed to the atmosphere and WILL rust your new APE studs if not installed. A worthwhile expense IMO.





Since the inner oil feeds don't get used Honda installed four small o-rings over the studs between the crankcase and cylinder. So four small o-rings and two large orings (six total o-rings) get installed between the crankcase and cylinder, as well as two knock pins. Make sure they are the longer pins.











Also make sure to install new o-rings around the cylinders. I like to lube all my o-rings with Parker O lube.





On my F3 since the oil feed is used only on the two outer studs I only need two knock pins. on each side of the cylinder. Its a common problem to get a new gasket that does not have the holes enlarged to accommodate the rubber gaskets that install around the knock pins like this.





I have read that those rubber knock pin gaskets are not a big deal to worry about and since my gasket is not cut to accept them I think I will just leave them out. I will install a VERY thin layer of Hylomar around this area instead just as insurance.


This is VERY VERY important and one of the reasons I had  a head gasket leak the first time around. When my head was decked I did not compensate for the material that was removed and my knock pins where to long. This prevented the head from full seating on the gasket and cylinder and caused me to blow a head gasket. MAKE SURE YOUR KNOCK PINS SIT FLUSH WITH THE CYLINDER SURFACE!

[brandEn]

Well after a "little" issue with a pulled cylinder stud thread    I am back on track.


After a few emails to some of the more knowledgeable wrenches on the CB750 I came to the conclusion of leaving my knock pins out completely.


Apparently, installing the knockpins and rubbers were a Honda band aid to fix leaky head gaskets. There is a Service Bulletin around here someplace stating this. Cometic gaskets make some of the best head gaskets in the industry and they make there head gaskets to be installed without the knockpins and rubbers. Do what you want with the information. I left mine out.


Pressing on with the cylinder install
Thanks MReick for these tips!!!
Rubber bands to hold the gasket in place. BRILLIANT!



I made some shims out of tongue depressors. BRILLIANT! Made installing the cylinders easy.

[brandEn]

Once the jugs are installed time for the head! Not much to say. I installed a VERY THIN layer of gasgacinch around some of the oil holes and cam chain tunnel.









Once the head is set torque your nuts! Ape recommends 20-22ft lbs for THEIR heavy duty studs. Make sure to follow the tightening sequence stated in the Honda manual.

I also recommend tightening everything in a three step process.


First Torque= 7 ft lbs
Second Torque= 14 ft lbs
Final Torque= 20-22 ft lbs





Now once everything is buttoned up. It was recommended to me to let the head sit for 24 hours. After 24 hours recheck final torque. I did this and everything was still tight.


After everything is good to go time to install some rubber pucks. These are a big source for oil leaks because they lead right out to atmosphere.


peek-a-boo!






I used Hylomar on my pucks



install your pucks, clean up the residual that squeezes out, and then install your cam towers!


Other tips I can offer,
-Check all your head threads. Heli-Coil any damaged ones. The soft aluminum pulls threads easily.
-Inspect your valve tappet adjuster screws. The tips can get damaged from years of use.




If anyone has any more suggestion please chime in. Also if anything I have posted is incorrect please let me know!

[Jerry Rxman Griffin aka MuthaF'er]

Now you tell me! Now that my engine is buttoned up. I know how to keep it from leaking - I won't put any oil in it and start it!    Damn, I was ~2 weeks away   

[brandEn]

Now you tell me! Now that my engine is buttoned up. I know how to keep it from leaking - I won't put any oil in it and start it!    Damn, I was ~2 weeks away   

Thats funny! However I suggest you put oil in it when you start it....  

[brandEn]

I found these pictures buried in the forum. I believe these were posted by MReick when he was doing some engine work for a member. I like the use of rubberbands here. I plan on trying this procedure. I have also fashioned some wood to use underneath the pistons to help prop them up when I go to install the jugs...


 

[brandEn]

So I need some tips here. What is everyone thoughts on using the Hylomar on the base and head gaskets?

[Old Scrambler]

Have only used Honda and Yamaha-bond in very thin coats..............This is a GREAT service you are documenting for us 'shade-tree' builders.  I buttoned up my K3 after a valve-grind and have mild oil leaks.............now I see why!

[brandEn]

Have only used Honda and Yamaha-bond in very thin coats..............This is a GREAT service you are documenting for us 'shade-tree' builders.  I buttoned up my K3 after a valve-grind and have mild oil leaks.............now I see why!

That's a great response and just what I need to hear. I was debating if this thread would get flamed or not. Thanks!

[brandEn]

Cycle X mentions in its tech tips that the eight "gaskets" item #2 are not required. Has anyone else NOT installed these?
note: there is only four required per the manual on my 78 F3. Early models required eight.





From the Cycle X Tech Tips FAQ
Question:
What is the purpose of those 8 rubbers around the studs between 1&2 and 3&4 cylinders ?
Do we need them, because we found an early cylinder in great condition?

Well, we would suspect Honda thought they needed those rubbers to help with potential weep-age in the head gasket area.
Personally, we feel heavy duty studs should have been used from the beginning ( like many other makes and models )
Maybe Honda felt HD studs were not cost effective during production.
But, early and later cylinders are interchangeable and if you follow the above mentioned procedures.......... you will be fine with-out them.
Thanks

[tweakin]

Dude, don't give away all the secrets....

Let me know if about Saturday.

[brandEn]

Dude, don't give away all the secrets....

Lete know if about Saturday.

No secrets should ever be kept when it comes to fixing friggin oil leaks!

[Jerry Rxman Griffin aka MuthaF'er]

I'm sorry but what could it hurt to use them!

My turn next. Hopefully I'll be firing up in a few weeks. None of the extra sealer in mine. Cross your fingers!

[Dimitri13]

Any chance you'll be doing a leak-free bottom end? That's where most of my oil is coming from

[jessezm]

So I need some tips here. What is everyone thoughts on using the Hylomar on the base and head gaskets?

I used Hylomar Blue in the aerosol spray on my head and base gaskets after after rebuilding my top-end twice and having a weep.  Results are that I have no leaks at the head anymore.  I did have a very small one at the base that went away, but I'm pretty sure I know what happened.  When you apply the spray, you have to do it very lightly in several coats.  With the base gasket, I started praying to close too the gasket and got a drip/high spot, which is where it leaked I believe.  But the leak went away after re-torque and a few hundred miles anyway.  I was much more careful about spraying the head gasket.  3 light layers on either side and let it cure.  I'm very pleased and will use it again.

[chewbacca5000]

I am surprised no one has mentioned resurfacing the head or cylinder block and the head is often warped from heat curing.  I had this on my 73 CB750 and asked for a minimal resurfacing of .005 per Hondamans instructions and the head was perfectly flat after.

Also, I did not use any goo in my engine except to seal the rubber pucks which shrink in time and end up leaking.  I do not like sealant as I can not work fast enough to get everything torqued down fast enough.  With heavy duty studs, two flat matting surfaces and O-Rings of the correct thickness for oil passageways there is no reason for a leak to develop at least on the older style heads.  Getting the correct orings is a big deal.  Do not automatically assume the ones with your kit will work as intended.

[brandEn]

I am surprised no one has mentioned resurfacing the head or cylinder block and the head is often warped from heat curing.  I had this on my 73 CB750 and asked for a minimal resurfacing of .005 per Hondamans instructions and the head was perfectly flat after.

Also, I did not use any goo in my engine except to seal the rubber pucks which shrink in time and end up leaking.  I do not like sealant as I can not work fast enough to get everything torqued down fast enough.  With heavy duty studs, two flat matting surfaces and O-Rings of the correct thickness for oil passageways there is no reason for a leak to develop at least on the older style heads.  Getting the correct orings is a big deal.  Do not automatically assume the ones with your kit will work as intended.

Good point and your absolutely right! I was getting to that during my next wrench session. My head is still mocked up for the studs to settle in. I was going to cover warpage and how to check for it as well as a few other items that can be a problem.

[Jerry E.]

My 1975 CB750F0 also has knock pins that are above the mating surface of the cylinders. I do not know the history of my engine, other than I have a 1973 K3 frame with a 1975 F0 engine in it. I thought I had a stock/original condition motor in need of some work. Does having longer knock pins mean my head was resurfaced at some point? Could this be a stock condition?   The head definitely doesn't sit flat on cylanders without a gasket on it.

[brandEn]

Well I suppose it could have been decked at some point. How much do they sit above the surface? There are 2 different sizes make sure you have the shorter ones installed.

[Jerry E.]

The head sits maybe .030-.050 off the cylinder deck. The knock pins were not removed before I tried the head on the cylinders, so if I have the wrong length ones, they came with the bike that way.  Would definitely explain the oil all over the motor, and the very low compression,( before I took motor apart), having the head held up that way.

[MCRider]

The head sits maybe .030-.050 off the cylinder deck. The knock pins were not removed before I tried the head on the cylinders, so if I have the wrong length ones, they came with the bike that way.  Would definitely explain the oil all over the motor, and the very low compression,( before I took motor apart), having the head held up that way.

Branden is correct. Rule of thumb is the 2 mating surfaces, whatever they are, should sit easily on each other with the knock pins in place and NO GASKET. If not you will get symptoms as you describe.

Sometimes it just crud in the holes. But on a clean reassembly, with clean holes, check you pin length. 40thou = 1mm. I think the knock pins are 2 mm diffferent from case/cyl to cyl/head. A microfish will tell you.

[brandEn]

Just wanted to bump my thread. It has gotten some attention lately and I just wanted to let everyone know that I don't mind if you all wanna post questions or discuss oil leaks in it! Hopefully the information I have posted here has helped at least one person and not caused any leaks for somebody else.

I would like to mention (again) that if anybody notices any mistakes in any of the above info PLEASE point it out! I would hate to give out bad advice and cause any issues for somebody.


P.S.
Its been a couple years and 5000 miles and my engine is still leak free...

[flybox1]

Great thread.....I'd like to add a simple heat shrink sleeving of the four 'exposed' studs can prevent rusting.
These are the studs under the acorn nuts and copper crush washers on the head.