Leaking head gasket

[Pescatore]

I am preparing to remove the left side head on a 1991 V65 with 21,000 miles.  It leaks oil and it's spreading all the way to the swing arm.
Compression is still 150psi on both sides when cold.
From the posts I have read, it seems a straight forward job.  I am armed with workshop manual and Guzziology.
I am expecting the head will not come off easily.  My question is about the cylinder base gasket.  It does not leak and I worry that prying the head off will compromise that joint.
What is the best way to remove the head without consequences?  Or is it a crapshoot?

The right side head is clean, so I don't plan on opening it.  However, I plan on taking the left head to a machine shop and have it taken apart, cleaned and checked out.
Does it make sense to remove the other head as well?  I guess I can do it at a later time, if I see differences in performance of the two sides.

[cappisj1]

Why you are at it… I would treat both sides to refurbished heads, head gaskets and base gaskets. You will be much happier in the end. The bike will be easier to tune and run much better in the end if you do both sides at once.

But if you only want to do one side you can probably not worry about the base gasket. But you’re only 15 minutes from pulling the jug, replacing the gasket and sliding the jug back on. Just need to collapse the rings when sliding it back on. If you don’t do it now it’s an afternoon worth of work to get back to the base gasket.

[Dirk_S]

Mind you, I’m only speaking from limited experience with a much newer V7 II, but I would have an extra base gasket on hand as a backup, and have a second set of hands hold down the cylinder while you take a combination of dowel, mallet, and prying device to work at the head.

[FarmallA]

When I first got my V65 Mongrel LaMonza  (Monza frame, Lemans tank, V65motor), the PO pointed out a leak from the right side jug, he thought it was the head gasket.  Turns out it was only the rocker cover gasket folded over.

But I assume you've checked that.

FarmallA
Steve

[Huzo]

When I first got my V65 Mongrel LaMonza  (Monza frame, Lemans tank, V65motor), the PO pointed out a leak from the right side jug, he thought it was the head gasket.  Turns out it was only the rocker cover gasket folded over.

But I assume you've checked that.

FarmallA
Steve

Good comment….

[Scout63]

Compared to that gearbox this is cake Maurilio. I wouldn’t freshen one head and not the other. Don’t forget that breather hoses come out of the back of the heads on the small blocks and into the air cleaner   Check to make sure that a hose isn’t cracked and blowing out oil by just removing the rocker cover. Also, gently tap the head with a hide or rubber mallet to loosen it. Don’t pry.

[normzone]

Also, gently tap the head with a hide or rubber mallet to loosen it. Don’t pry.

Only commenting to say that also, breaking fins is unfortunately easy ... 

[nsmith]

Never tried it but what would happen if after removing the push rods and of course the nuts and bolts you put the sparkplug in and crank the motor over? 150 psi should blow the head clean off as Dirty Harry would say.

[acguzzi]

probably separate the assembly at the base gasket unfortunately since it's the smaller of the two, neat idea though!

[guido guzzi]

Never tried it but what would happen if after removing the push rods and of course the nuts and bolts you put the sparkplug in and crank the motor over? 150 psi should blow the head clean off as Dirty Harry would say.

Hold my beer...

[n3303j]

Hold my beer!
Was when you just loosen all the head nuts about 1 millimeter and crank it over live. Each cylinder fires once and the heads are free!

[Scout63]

Ear muffs Pescatore.

[Murray]

Hold my beer!
Was when you just loosen all the head nuts about 1 millimeter and crank it over live. Each cylinder fires once and the heads are free!

Well you could go a threaded compression tester and some compressed air, I'd leave the head bolts in a few threads. Not sure about the V65 but on the old square fin big blocks there is a blanking plug that allows access to a head bolt (I think) sealed with an o-rung. When that leaks it looks remarkably like a head gasket.

[Frenchfrog]

Nothing like that on the smallblocs

[Pescatore]

This is getting very entertaining. I'm holding the beer, nsmith.  Did it work?
Compressed air from the spark plug is interesting too.

Thanks for the tips, folks. I was thinking about prying the head, so I won't push on the fins.  Holding the cylinder makes sense.  Compressed air should keep the cylinder down as well.
I have a whole gasket kit from Scout63 and the valve cover gasket is dry.

I'm overthinking it because I'm in the camp of not fixing what's not broken. And I've been tearing and rebuilding this bike for the past 4 winters.  Exactly one year ago, Scout63 helped me fix the gear box.
And there's more to do.  Front shocks seals and a leaky carburetor plug. No idea what to do on the latter.

Anyway, I have tools, manuals, parts, space, support, money and no flipping time to do it.
So it might take a while, but I'll git'er done.

[Huzo]

Never tried it but what would happen if after removing the push rods and of course the nuts and bolts you put the sparkplug in and crank the motor over? 150 psi should blow the head clean off as Dirty Harry would say.

Wouldn’t you need to leave the pushrods in or else there’ll be no mixture in there to compress, since the inlet valve won’t open.

While we’re having fun…
If your cylinder swept volume is 325 cc and compression ratio is 10:1, you would have 32 cc volume in the combustion chamber (give or take).
Just upend 50 cc of oil in the pot, remove the exhaust pushrod, remove the head retaining nuts, put the plug back in and fire it on the live one….!
The hydraulic lock should bash it free….. (what could possibly go wrong..?)

[Vagrant]

Finger nail polish should stop the plug leak.

[sign216]

I recall Richardson talked about smallblock head gasket leaks.  Here is my summary, from another website; 

Head Gasket Leaks - The distance between the studs is long and the gasket web is thin, so leaks happen, especially on the outward side near the oil passage. I've solved leaks with Permatex Super 300, as recommended in Guzziology by Dave Richardson.

Take off the head, apply Super 300 to both sides of the head gasket with a little extra in the problematic bottom part, near the oil passage. Wait a short time for it get tacky, and bolt everything back up. I've had luck re-using the old gasket if it looks decent. Torque again.

Base Gasket Leak - Richardson reports that a during manufacturing a drilled stud hole can break into an oil passage, causing base gasket leaks. The fix is to clean the hole, seal stud with Loctite, and reassemble. I refer you to Guzziology for photos and details.

[Pescatore]

I was thinking I don't need ignition, just the piston compression. Your idea sounds more fun, Huzo.
That's one way of decorating the bike with oil and  shooting the head across the garage.

Thanks for the Guzziology reference.
I remember reading about the Permatex for valve covers as well.
Does Permatex harden and make it difficult to remove the gasket later?

[sign216]

Reportedly Permatex does not harden, but nothing is eternal, right?  I used it years ago, and I would say it slooowly hardens, over years.

[John A]

We used to use it on iron exhaust manifolds when they had a divot on the sealing flange or were warped and wouldn’t seal with a new gasket. In that application it got hard and generally worked well.