Topic: Senior project for high school - 78 CB750K

[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.

[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.

[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...

[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.

[Restoration Fan]

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.

That's our plan on the smaller items, but that frame is a little big to hold up in the air and move around to grind with a bench grinder. 

We actually bought a package of various sized wire wheels from Harbor Freight that fit in a drill chuck and used those to get the majority of the paint off the frame.  I agree with you though that the wire wheels work a bit better than the sandpaper but we still felt like we needed to go back over the frame and wet sand everything lightly as the final prep stage before paint.

[70CB750]

There are many ways to skin the cat i use angle grinder, it spins about 11000 and works well.

[madmtnmotors]

Here's the results of "lapping" the head over glass on the "elbow mill":

http://forums.sohc4.net/index.php?topic=100352.msg1615472#msg1615472

[Restoration Fan]

Here's the results of "lapping" the head over glass on the "elbow mill":

http://forums.sohc4.net/index.php?topic=100352.msg1615472#msg1615472

Very cool!  I had never seen this method before but it seems like it would be one of the safest methods to ensure that you don't gouge into the soft metal like it's possible to do with razor blades or the other methods I've found.

[Restoration Fan]

We've been doing lots of sanding, polishing and generally just cleaning up more parts to get ready for paint.  Trying to take advantage of the warm weather to get the painted pieces done.

I don't know how many of you know about a product called Metal Rescue, but I stumbled across an advertisement for it back in August when we first bought the bike.  I found a Home Depot that carried it not too far away and bought a gallon of it ($25) to see if it would help remove the rust on some of these things.  Well, I finally decided to try it out yesterday on the shocks that came on the bike.  WOW.  I'm impressed.  This stuff is non-caustic so you can get it on your hands without it burning them.  It can be dumped out and it doesn't hurt the environment and it also doesn't affect rubber or plastic negatively so you don't have to remove all those bits from the piece.  All you have to do is let it soak.  Take it out and clean it off every couple of hours and put it back in to soak. 

Before & after photos of the shocks below.  This is with absolutely zero polishing or sanding.....only soaked and rubbed clean.  (Well, in truth, I did go through about 3 or 4 shop towels as I wiped the grunge off every time I would remove it from soaking.)

If anyone is interested, I included a photo of the Metal Rescue gallon jug.  I bought mine at Home Depot but not all of them carry it.  You can go to http://www.metalrescue.com and look up the list of distributors near you if you are interested.  Oh yeah...the stuff can be run through a strainer to clean out the dirt that accumulates in it and reused over and over.  If you get a chance, watch their video on that site where they soak an old, rusty Tonka truck and see how it looks before and after.  I'm sold on it.  Gonna be buying another couple of gallons to see if it will take the rust off these spokes on the rims.

Also including a photo of the top of the triple tree that's almost ready for painting.

[grcamna2]

Good morn., 
I'm interested in that 'metal rescue' now  myself ! were you able to soak the rear shocks in those tubs w/ no ill affects to the rest of the shocks ? and did that product remove the paint from your top triple ? How long did it take to get'em that nice ? Thanks, looking good 

[Restoration Fan]

Good morn., 
I'm interested in that 'metal rescue' now  myself ! were you able to soak the rear shocks in those tubs w/ no ill affects to the rest of the shocks ? and did that product remove the paint from your top triple ? How long did it take to get'em that nice ? Thanks, looking good 

No, I didn't use the Metal Rescue on the triple tree.  It's purely for rust removal, not paint removal.  Those, we used a wire wheel on, after applying aircraft stripper.

As far as the shocks, it worked like a charm on them.  The rubber bushings inside the top hole (is that the cleavis?) are completely intact with no ill effect to them.  They claim as such on their site and commercials but I was skeptical until I saw it myself.

As far as timing, they tell you that the time involved is different, depending on the amount of rust.  I put the shocks in at 4:30 yesterday afternoon.  After 2 hours, I took them out and cleaned them off.  Did the same every 2 hours until 10:30 last night.  Then I put them in overnight to soak one more time.  When I got up this morning, I went and removed them from the solution and dried them off with a shop towel.  Then I took the photos.

On that video I mentioned, I think they ended up leaving that Tonka truck in the solution for a total of about 2 days to get rid of all of the rust.  You have to stop and strain out the solution when it gets really dirty but other than that, it's pretty much a fire and forget product. 

Here's the video link.  I saw they have put up a lot more testimonial videos on their site, so I went and looked this one up to make it easier for you guys.  This is the video that convinced me to go buy the product & try it.
https://www.youtube.com/watch?v=JAI5SF3NBqg

[Restoration Fan]

The 4 nuts on the rear wheel all have a small tab on the nut, which make it such that a socket doesn't want to seat on the nut properly to try & turn the nut to remove it.  Are we supposed to pop that tab up or something in order to remove that nut?