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Discussion Starter · #1 ·
Hey gang, I have the head and other assorted pieces off my 79 CM400T and I'm trying to remove the cylinders to replace the base gasket but the thing is stuck. I've gone around it with a rubber mallet, pried with a large flat blade screwdriver and its not budging one bit. The motor is out of the bike sitting on a work table presently so I have pretty clear access to everything. Any ideas?
 

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Any bolts you missed?
Are the pistons free, as in it still turns over?

I've always used PB Blaster to unlock engines, but it will ruin rubber seals if used in excess.

Pictures are worth a thousand words you know... :lol:

GB :mrgreen:
 

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Discussion Starter · #3 ·
There are no bolts left, the long head bolts that hold the rocker assemblies also fasten the head and cylinder to the cases. I didn't put up any pics figuring you fellas could picture these motors in your sleep :lol:

Pistons are free, turns over nicely, just pulling it apart to fix an oil leak.


If need be I can get some pictures.
 

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Somebody in the past probably used the dreaded Permatex gasket goo on the base gasket. There has been a lot of cursing and blood shed over the years because of that stuff. Your going to have to get a little more forceful to get it apart, then getting the old gasket off will be a chore. Good luck!!!
 

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Discussion Starter · #7 ·
Going to be picking up a propane torch in the near future then. There are solid tabs that stick out around the base of the cylinder in 2 places on each side. These tabs seem like a decent pry point if need be. They don't line up with anything.

You can see the tabs in this picture, they are the clean areas in the front.



(Borrowed from E-Bay)
 

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Bryan -

I wouldn't get too aggresive with the prying on those points.
That aluminum is very soft and a screwdriver or other tool will make horrible gouges.
I would continue whacking with a rubber mallet, then if you could get even the slightest crack to appear, try some wooden or plastic wedges. And the heat may help, who knows.
If it does have that old Permatex, it's truly horrible stuff, it basically turns to epoxy after a few years. Of course, it may just be bare gasket, you never know.....

You're experiencing a really common problem with these old bikes - that gasket has been there for a very long time.
In the past it's always been the "shock" value of the rubber hammer that's ultimately broken them free, for me at least.

Your problems are only just beginning, as once you have it broken free, you'll have to scrape the old gasket off, which will literally take hours and hours.
You may in fact end up just leaving the old gasket on there and applying a judicious (meaning small) amount of silicon.
It's always a toss-up between the benefits of a new gasket and the potential damage that could be done (which could be significant) in scraping the old one off........
 

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Discussion Starter · #9 ·
I just went around the base with PB blaster and will let that sit. Just dropped off the head at a local machine shop so they can extract 3 of the 4 exhaust studs that are stuck/stripped/broken. Figured I should take it to a professional before buggering up the head with trying to drill them out. I'll stay away from the prying then and keep working around with a rubber mallet.


Would using a brillo type pad harm the gasket mating surfaces? I have some that mount on my dremel or a drill. I do have plastic scraping tools as well. Isn't there such a product as gasket remover that helps break it down?
 

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Somebody here did post a link for some gasket-softening spray stuff here recently - can't remember who or where. I have no personal experience with it.
You can forget the plastic scraper, it will get you nowhere with this stuff.
Brillo probably wouldn't make much of a dent in it either, unless you have about a hundred years to work on it - it's really unbelievable how hard these old gaskets are to get off......It's my single biggest nightmare/PIB on any old engine....
 

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I know this is a necro post, but I just went through this a few weeks ago. I tried everything, blocks of wood beating the crap out of it, cursing at it, booting the living hell out of it....nothing worked. Screwdriver, prybar, etc...all failed!

I got really pissed and grabbed an old hatchet and wedged it under the front edge an beat on it HARD with a hammer. Finally the damn cylinder separated from the case!
 

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Sometimes, regular brush-on paint stripper does a good job of softening those old gaskets and making them easier to remove. I use a cheap artist's paint brush to apply it in a controlled manner. Let it soak long enough to do its job, before you start scraping. I have also had good luck using a soft, rotary brass brush in my Dremel Tool. I think the brand name is Irwin (not sure about that), but I buy them at Ace Hardware. You have to be careful that they have the 1/8" shank size to fit the Dremel. These brass brushes don't mar the aluminum gasket surfaces. They are also very good at removing surface rust from chrome, without scratching the chrome itself. Use them at moderate to low speed, and with light pressure. Excessive speed will be evident by flying brass wires -- wear safety glasses for sure! Too much pressure will leave marks on the chrome.

Funny how I used to sneer at Dremel Tools -- thought they were useless because they were so small. After I got one, I reach for it all the time. They aren't just labor saving devices, there are things you can fix on old motorcycles with these tools that I cannot imagine any other way to accomplish. Another example that comes to mind is that I recently laced up a set of spoke wheels. When it was time to grind off the ends of the spokes where they protruded through the nipples, the Dremel with a carbide cut-off wheel was the only thing I could get in there without damaging the wheel rim. Very handy!
 

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I don't think a dremel or liquid gasket remover would help me pry the metal off :) My cylinders were sealed onto the engine case so tightly there really wasn't much of a gap. For cleaning the sufaces afterward it sure helps though. I just use kerosene, windex, and the green or blue scotch pads with a razor blade (carefully) as required. I'm not sure I'd trust myself with a really fast spinning tool on a mating surface like that in the home environment. Some probably wouldn't even use a razor blade.
 
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