Topic: Extremely stuck head gasket

[Ericcb750]

Hello Guys, I know this one maybe a long shot but here we go... I have a motor (77/78) CB750k that I got from a friend ( full motor). I'm at the point where i'm ready to separate the head from the cylinders. This head is SO STUCK on it's crazy.... Oh and to make things just that much easier, one of the pistons (could be more) is stuck in the cylinder so I can't turn the motor over.

I want to try and avoid breaking any fins or damaging the head/cylinder mating surfaces as much as possible. I want to see if you guys have any tips or advice that may be able to help me free this very sticky gasket so I can get the head off and continue to break down this engine? I've taken a couple apart before but none that were like this...There is ZERO Leaking in the pucks or head gasket which would probably have helped a little at this point.

Any help/advice would be greatly appreciated. Thank you very much.

[BomberMann650]

Have you tried anything to free the stuck piston yet?  Couldn't hurt.

I've been a fan of sending some light shocks through gasketed parts via rubber mallet.  Don't know if you've tried that.

[Duanob]

Frankly I would try and un-stick the pistons before taking the head off. Use the gearing by rocking back and forth after pouring a mix of ATF and acetone or some similar concoction into the cylinders via spark plug holes. Let it sit for a couple of days then rock the bike if you can in gear. Once you get it moving then you can remove the head and jugs way easier without damaging anything.

[DaveBarbier]

Frankly I would try and un-stick the pistons before taking the head off. Use the gearing by rocking back and forth after pouring a mix of ATF and acetone or some similar concoction into the cylinders via spark plug holes. Let it sit for a couple of days then rock the bike if you can in gear. Once you get it moving then you can remove the head and jugs way easier without damaging anything.

+1

And if you get the pistons unstuck first they can help you remove the head by using a cotton cord in the cylinders and bumping the starter or using a wrench on the rotor bolt.

[madmtnmotors]

    The last one that gave me trouble took me two days and broke two fins. Some freaking goob had slathered some kind of industrial adhesive on both sides of the gasket prior to install. Sheer brute force was the only thing the separated the two, and the head gasket actually delaminated with exactly half the gasket stuck to the head and the other half the gasket stuck to the cylinders. There are not too many places that will tolerate that much force, especially across the front of the motor. It was near the exhaust ports where I snapped a small piece off of two different fins. I finally found the meatiest section of both the head and cylinders on the backside, below the intake ports (number two and three I think) where I inserted a pry bar and just leaned on it for a while. Ever soooooo slowly the gasket began to delaminate and I was finally able to separate the two.
 
    It took me two more days to get the damn gasket scraped off. 


    Make sure you have removed all six of the 6mm bolts, the four under the cam towers and the one in the center front and the one in the center rear. It would take a whole lot of force to overcome any bolts that might remain!   

[camelman]

I often use a penknife with the edge of blade touching the gasket. Then, i tap on it lightly with a hammer, socket extension, or whatever fits. It exerts a phenomenal amount of force and splits the head off without effort. Make sure to use a thin blade.

Camelman

[BomberMann650]

All that winching madmtn did makes me wonder if it'd be possible to pass something thru the air ducts then fashion a mechanical spreader?

[jonda500]

I often use a penknife with the edge of blade touching the gasket. Then, i tap on it lightly with a hammer, socket extension, or whatever fits. It exerts a phenomenal amount of force and splits the head off without effort. Make sure to use a thin blade.

Camelman

+1 -this is better than trying to use the rope and raising the pistons method as that would tend to raise the barrels & head together without unsticking the head gasket!
John

[Ericcb750]

Good morning guys. Thank you all very much for your help/replies. I really do appreciate it. I like getting everyone's tips and tricks as there's a lot already that I would not have thought of.... I guess I got lucky on my 78K that the head gasket was leaking and came off very easily. I will be patient and try different methods to remove it.

I really want to avoid breaking/damaging anything as it always saddens me when some of these old parts get broken. I will try to mix and match a bunch of the different methods described....I think the first will be to soak the cylinders and see if I can free them up a bit. I did make sure to remove all the nuts/bolts from the head including those under the cam tower pucks and the front and rear between #2 & #3.

I'll keep at it and i'm sure it will give up at some point.....Thank you all again very much...This forum is the absolute best and it's all you guys that make it that way....always willing to help out another member, especially someone whose a little newer to these bikes, I appreciate that. Take it easy. Please keep the ideas coming. Thanks
  - Eric