removing a stuck head

[squarecat]

Hey guys, I've done some digging and couldn't find anything that addressed this so please forgive me if it has and i missed it:

Im tearing down my 78 xs400 motor and got the timing chain, ohc, valve cover, and top head removed successfully, but I'm struggling to get the bottom head section separated from the block (i don't think its ever been done to this before). It is firmly sealed and not coming apart. the manual recommends a mallet which i tried. i just don't want to screw up the fins etc. any tips/tricks anyone has for separating the two without damaging either?

thanks!

 

[MrStubb]

Grab your self a short section of 2x4 place it just under where the head seperates from the jug. Give it a little persuasion with a few love taps from your mallet. Don't hit it too hard you don't want to damage any thing but it will take some muscle. I've done this with other engines and the gaskets do get stubborn.
First Be sure that you have taken ALL of the bolts out or you will do damage. Some bolts are well hidden.

 

[Jeff0133]

Maybe the pistons are seized in the cylinder? put a little oil in the cylinder and move the pistons around by turning the crank with a ratchet...maybe a little easier if the pistons aren't dry in the cylinders

 

[squarecat]

hmmm bolts are removed, and pistons are moving. ive tapped it a few times but concerned about breaking fins. i read somewhere about using plastic wedges (door wedges from home depot) to get in the seam. anyone have any luck with a similar approach? i may give that a go.

 

[Greasey Fingers]

Hey what I did was got a thin paint scraper and gently tapped it between the head and the crankcase, starting on a corner. Then worked my way around until the head started to pry off easilly by just using your hands and pulling on it.

Once the seal is broken in one area the rest comes apart pretty easy. You wont need to use the scraper all the way around, just enough in one corner for it to break the initial seal.

You destroy the old gasket but are replacing it anyway. The surface was fine afterwards, I was worried about damaging the mating surface but it didnt at all, just mashed the old gasket. It rebuilt fine afterwards with no leaks whatsoever.

Its good you didnt continue hitting it with a mallet. When its stuck like that you will break a fin like I did lol. My head was stuck real good, pretty much as stuck as they can be.

I used something similar to this, worked a treat and was very easy:

 

[squarecat]

ah cool thanks! i'll give that a go.

 

[alastairuk]

If you're talking about the cylinder barrels, I had a similar issue. I smacked it around with a mallet to no success, then I sprayed the pistons with wd-40 and turned the engine over by hand before leaving the engine sitting upside down for a day or two. Then I just secured the base and grabbed onto the bottom fin on the front and back and wiggled it side to side. It came right up after that. I don't know if anything I did helped or if it was just environmental changes, but I figure it's worth a try.