Topic: Senior project for high school - 78 CB750K

[Stoli]

Keep at it. Don't rush it or you will start breaking fins. Persistence. Find the solid pry points and give equal attention to all sides. Eventually it will give way. 

Hate to mention this but now that you have the top end apart, might want to consider HD studs. Min cost is around $80 for the APE studs. Z1 is the lowest price I have found. In my opinion, a key ingredient to prevent head leaks. If you decide to go there, ask me about stud removal before you start in. There is the easy way and the hard way and I can tell you the easy way. Namely a $15 stud removal tool on Amazon that is worth every penny and then some.

[calj737]

A great trick for separating the head from the jugs is to stuff the chambers with some rope, then rotate the crank. The piston will compress the rope and forced the head up and away from the jugs. You don't need much and ordinary cotton rope works well.

[seanbarney41]

Excellent.  Thank you.

OK, another question though.  We have made the decision to at the very least, lap the valves.  So we have removed cam shaft.  We also removed the 22 nuts holding the head on, but how do you get the head to separate from the jugs?

Conscious of not breaking the fins, we were tapping gently on the various places on the head.  But it looks like the jugs are starting to separate slightly from the bottom...but the jugs aren't separating from the head.  How do you guys get those to separate?

in addition to the 22 nuts there is a couple regular 6mm/10 mm hex head bolts, you did not forget them?

[Restoration Fan]

Excellent.  Thank you.

OK, another question though.  We have made the decision to at the very least, lap the valves.  So we have removed cam shaft.  We also removed the 22 nuts holding the head on, but how do you get the head to separate from the jugs?

Conscious of not breaking the fins, we were tapping gently on the various places on the head.  But it looks like the jugs are starting to separate slightly from the bottom...but the jugs aren't separating from the head.  How do you guys get those to separate?

in addition to the 22 nuts there is a couple regular 6mm/10 mm hex head bolts, you did not forget them?

We didn't forget them.  There are actually 16 regular nuts and 4 of the 6mm under the rubber diaphragms and the 2 10mm hex head bolts.  We got them all off.  But thanks for the suggestion; I really do appreciate it.

[Restoration Fan]

SUCCESS!!!!  We got the head off pretty easily after reading that thread, Steve-O.  Thanks for posting it.

Cal, I wish we had seen your idea before we started; that sounds like a great idea.

I first tried Hondaman's idea of using a sharp knife to cut the head gasket.  I went all the way around to make a small cut with the knife, but when I got the side just over the points plate, my son noticed a small gap there.  We inserted a very thin flathead screwdriver and lightly tapped it in about a half inch and the seal was broken.
So then we were able to pull the head off easily.

Below are photos of the pistons and valves right after coming off the engine, and then after a very light cleaning with carb/parts cleaner. 

The pistons and cylinders look incredibly good.  As a matter of fact, they look good enough and the camshaft was in such good shape that we are now thinking that we will only lap the valves and then button the top of the engine back up after cleaning up surfaces, etc.

Regardless, there's a LOT of cleaning to do but overall, very encouraged with how the inside of the engine is looking.  Thanks to all of you guys once again for your willingness to offer advice & encouragement. 

[Stev-o]

Success!   Now clean clean clean....

[Restoration Fan]

Success!   Now clean clean clean....

Yes.  LOL.  Once we got the head off last night, we decided to "just knock a bit of the grease off of it" with some carb cleaner and degreaser.  After about 30 minutes, I happened to glance at my phone and noticed it was 11:30 on a school night.

Someone was NOT happy to have to stop working on it and go to bed but such is life.  We'll get back on it this afternoon.

[calj737]

Maybe 11:30 on a scholl night is late, but I'd rather my son (I have 3 +1) was spending time with me, involved in something he was very enthused about, and learning to solve problems, than squirreled away on Xbox, or texting until 10:00.

At least tonight you'll know what the topic of his dreams are  And it will be a long time before his enthusiasm wanes, I guarantee it-

[Davidov]

SUCCESS!!!!  We got the head off pretty easily after reading that thread, Steve-O.  Thanks for posting it.

Cal, I wish we had seen your idea before we started; that sounds like a great idea.

I first tried Hondaman's idea of using a sharp knife to cut the head gasket.  I went all the way around to make a small cut with the knife, but when I got the side just over the points plate, my son noticed a small gap there.  We inserted a very thin flathead screwdriver and lightly tapped it in about a half inch and the seal was broken.
So then we were able to pull the head off easily.

Below are photos of the pistons and valves right after coming off the engine, and then after a very light cleaning with carb/parts cleaner. 

The pistons and cylinders look incredibly good.  As a matter of fact, they look good enough and the camshaft was in such good shape that we are now thinking that we will only lap the valves and then button the top of the engine back up after cleaning up surfaces, etc.

Regardless, there's a LOT of cleaning to do but overall, very encouraged with how the inside of the engine is looking.  Thanks to all of you guys once again for your willingness to offer advice & encouragement.

How do the cylinder walls look? Can you seen definite cross-hatch lines? It's hard for me to tell just from the pictures.

I would measure cylinders and pistons as your starting point. If you find they are in serviceable specs, then hone and install new rings.

+1 on HD studs

[grcamna2]

SUCCESS!!!!  We got the head off pretty easily after reading that thread, Steve-O.  Thanks for posting it.

Cal, I wish we had seen your idea before we started; that sounds like a great idea.

I first tried Hondaman's idea of using a sharp knife to cut the head gasket.  I went all the way around to make a small cut with the knife, but when I got the side just over the points plate, my son noticed a small gap there.  We inserted a very thin flathead screwdriver and lightly tapped it in about a half inch and the seal was broken.
So then we were able to pull the head off easily.

Below are photos of the pistons and valves right after coming off the engine, and then after a very light cleaning with carb/parts cleaner. 

The pistons and cylinders look incredibly good.  As a matter of fact, they look good enough and the camshaft was in such good shape that we are now thinking that we will only lap the valves and then button the top of the engine back up after cleaning up surfaces, etc.

Regardless, there's a LOT of cleaning to do but overall, very encouraged with how the inside of the engine is looking.  Thanks to all of you guys once again for your willingness to offer advice & encouragement.

How do the cylinder walls look? Can you seen definite cross-hatch lines? It's hard for me to tell just from the pictures.

I would measure cylinders and pistons as your starting point. If you find they are in serviceable specs, then hone and install new rings.

+1 on HD studs

+1 

[Stoli]

Looks like you are all in.

Stud removal - if you decide to do it, get one of these:



http://www.amazon.com/Powerbuilt-648639-Stud-Extractor/dp/B002INQORU/ref=sr_1_6?ie=UTF8&qid=1413405129&sr=8-6&keywords=stud+remover

The upside is that you are far more likely to get a leak-free head gasket for years to come. I can see from the pics that oil was leaking from somewhere in the head (gasket or pucks or maybe both). The stock studs on these engines are thin, as you can see, and they tended to stretch allowing the head gasket to leak. The HD studs are stronger and have a higher torque rating. Much less likely to leak.

The downside is if you break a stud, things get complicated.

Technique - The night before removal, put a little bit of PB Blaster, Mystery Oil, or ATF/Acetone (50/50) solution around the base of each stud then hit the studs just above the base with a Mapp torch for 30 seconds or so each. The oil will vaporize under the heat so put some more on there to sit overnight. Don't rest the remover tool directly on the gasket surface of the upper crankcase or you will mar it, so elevate it with a small block of wood or something so when you twist each stud out, the tool doesn't mar the case. I have used this technique on my last 3 engines (48 studs) without incident. If you get a troublemaker, hit the case around the base of the stud with the Mapp torch for a minute or so just before removal. I didn't know about the tool on my 1st rebuild and used the double-nut technique. It worked but it was soooo much easier with the $15 tool. Whatever you do, don't use that crazy suggestion about bending each stud 90 degrees to twist them out. Much more likely to break something that way.

The old gasket material can be difficult to remove without marring the gasket surface of the head, jugs and case. Try using the aircraft paint stripper. It might take 5 application/scrape passes in the thicker areas but it does help to soften the old gasket for easier removal. It doesn't penetrate the old gasket material as well as it does paint so that is why you might have to make 5 passes or so.

When you are ready for reassembly, read through this:

http://forums.sohc4.net/index.php?topic=107040.0

The top end of your K is slightly different from the F that he has but all the important stuff is the same. The gasket compound and gasket brands, etc that he recommends aren't gospel but it is a really good summary of everything you should do on your top end.

[Stoli]

One more thing - don't do anything to your engine just because me or someone else recommends it. Read up and make the call. We all want to help but what works for some doesn't work for others and opinions can vary greatly. Some will recommend not to replace your studs. Your call. Another good, for instance, is the step in the "leak free top end" thread where branden uses loctite on the cylinder studs. I don't understand why you would need to do that on something that is so difficult to remove anyways. I go by the manufacturer's suggestion and just use a bit of oil. The less things you introduce into these engines, the less likely you are to get a clogged oil passage and in my opinion, manufacturers tend to know best. They recommend oil so that is what I use.

Oh, and in case I haven't mentioned it before, I recommend that you never ever use a torque wrench on a 6mm bolt while rebuilding this engine. By all means, use the torque wrench on the cylinder stud nuts as per brandens suggestion but just hand tighten the smaller bolts with a 1/4" socket wrench. It is real easy to strip the 6mm threads with a torque wrench.

[calj737]

....for instance, is the step in the "leak free top end" thread where branden uses loctite on the cylinder studs. I don't understand why you would need to do that on something that is so difficult to remove anyways.

The reason you use LocTite on studs is twofold: one to prevent corrosion and galling, and the other to prevent them from being unscrewed when a rusted nut is loosened on the other end in the future. It does also help with obtaining full torque in some people's opinion.

[Stoli]

I wish the studs came out when I unscrewed the nuts. That would have actually made things much easier. 

[Restoration Fan]

So the manual says to use an oil stone to clean the surfaces.  Is that how you guys do it?

[Stoli]

I don't have an oil stone but maybe that is what works best because I have tried a lot of things and nothing has really worked all that good. I use the aircraft stripper and a stack of razor blades. The steel blades can knick the aluminum surface fairly easily so you have to be real careful. A dull blade is more apt to scratch the surface so as soon as a blade gets a little dull, I open a new one.

[grcamna2]

So the manual says to use an oil stone to clean the surfaces.  Is that how you guys do it?

I never did it that way, but I can see how a long-block oilstone like that would certainly keep the surface flat as you're cleaning away the last bit of gasket material. I need to remember to clean that hard cement-like old gasket material in stages so I won't change the mating surface of the cylinder head,etc. I generally use a few safety razors and slowly & evenly smooth it down until I come to the original surface;I tend to use up a lot of blades that way...

[calj737]

I use Rol-Loc discs in a small air grinder. They are not coarse enough to damage the mating surface, but are stiff enough to breeze right through the gasket. Of course, you could also head blast the head or soda blast it since your undertaking some lapping what not.

But I like the Rol-Loc and ScotchBrite pad method personally.

[madmtnmotors]

So the manual says to use an oil stone to clean the surfaces.  Is that how you guys do it?

I use a thick piece of tempered glass (about 3/8" thick) coated with lapping compound after scraping as much as possible. The Permatex water based works best for me, add a spritz of water to make a thin paste and swirl the head around on the glass until the head is smooth. Usually have to refresh the paste a couple times, but it sure does leave a purty (and smooth!) finish. I'll probably be doing one this weekend so I'll post some picts in my "Evolution" build thread of the before and after.

[Restoration Fan]

So the manual says to use an oil stone to clean the surfaces.  Is that how you guys do it?

I use a thick piece of tempered glass (about 3/8" thick) coated with lapping compound after scraping as much as possible. The Permatex water based works best for me, add a spritz of water to make a thin paste and swirl the head around on the glass until the head is smooth. Usually have to refresh the paste a couple times, but it sure does leave a purty (and smooth!) finish. I'll probably be doing one this weekend so I'll post some picts in my "Evolution" build thread of the before and after.

Some very cool methods here.  I'll definitely be looking to see the pictures.  Thanks.

[Restoration Fan]

Wife got home from Bali on Friday, so the ability to work on the bike over the weekend was severely hampered.

Oh yeah...what an idiot I was.  I thought the frame would be ready for paint in a day or two.  Man, how many little nooks and crannies are there on that thing, LOL?  After hours of sanding with a palm sander and wire wheels, plus two coats of aircraft stripper, it's finally starting to get close.  At this rate, I'm guessing we have only another week or two for it to be ready.   
Just kidding.  I think one more coat of stripper tomorrow, followed by some light sanding and we should be ready for primer on Wednesday or Thursday at the latest.

One other thing affecting our ability to work on the bike has been the amount of homework his teachers have been assigning him in his AP classes.  I think I'm going to have to write them a note and explain that some things are more important than homework!

Also, we went ahead ahead and pulled the cylinders and found out an answer to one of our questions.  The gasket that goes on the bottom of the cylinders, between the cylinders and the bottom, that gasket was in pieces.  And it was those gasket pieces that were in the bottom of the oil pan.  So the foreign debris I was worried about earlier in the build thread has now been identified.

Everything looks good there so far.  Since we have the jugs off, we're now working on cleaning those and the heads to get them ready for painting later.  We still have to remove the valves and valve springs but need to buy a valve spring compressor to do that.  Will pretty much any valve spring compressor do or should we buy one specific to these Hondas?  Also, since we have the cylinders off, we're going to go ahead and get the APE studs and replace the ones in there now with them.  Also means I'll be buying that tool that Stoli recommended (thanks for that, by the way!).

All in all, things are going a bit more slowly than anticipated but we're trying to make sure we really take our time and don't rush anything and mess it up.  The best thing about that is that we're getting to spend more time together working on it...and that's never a bad thing.

[Stoli]

Call around to the auto parts stores in your area and see if they have loaners (valve spring compressor). In my area, there is an Advance Auto Parts store which loans out tools like that. You leave a deposit ($70) and get it back when you return the tool. Since I was rebuilding so many engines, I broke down and bought one. If you strike out on a loaner, this is the one I bought:




http://www.amazon.com/OTC-4572-Large-Spring-Compressor/dp/B000F5ECUY/ref=sr_1_1?ie=UTF8&qid=1413901225&sr=8-1&keywords=valve+spring+compressor.

It works really well on the CB750 head.

[Restoration Fan]

Excellent.  Thanks, Stoli.

We're making some progress.  Got the frame and swing arm painted today.  We still have to wait a couple of hours before it's dry enough to take it back down to the workshop.

We also got the lower part of the head cleaned.  Now I'll go buy that valve spring compressor so we can take the springs off and lap the valves.

[grcamna2]

Nice work on painting that frame;folks who paint 'autobody only' have got nothing on us !
There's a lot more surfaces to paint on a frame than on a flat outer automobile exterior   

[70CB750]

Looking really good!

I usually use wire wheel to strip paint from steel, unlike sandpaper it does very little to the metal and it goes fast  - knotted wire wheel on a grinder that is.