'80 XJ650 head gasket :(

Hey folks..


Well, I put a few miles on my "new" '80 XJ650, and noticed that my head gasket is leaking a bit of oil on the right side. I'm 100% certain that it's not the valve cover gasket. I can start it up, rev it a bit, and watch oil perspire out of a couple of places right on the side of the head gasket. There's no compression loss, and it runs great, but this being a Japanese bike, I figure it shouldn't be leaking anything :mrgreen:

This, of course, means that I'll be replacing the head gasket soon. I've tried re-torquing the acorn nuts (23.1 ft/lb was what I found in the Haynes book), to no avail. The good news is that there's not a single corroded bolt on that engine. All exhaust, intake, valve cover and head bolts will break loose with little effort.

I guess I need to start sourcing all the necessary parts.. Anything special I should look for, besides the head gasket?

Has anyone had any luck with temporary fixes, like lifting the head slightly with cam chain tensioner removed, and applying some Ultra Copper or something?



Thanks in advance..

stereo

 

In all honesty ther are no temporary fixes to a head gaket that are worth doing.
Send a PM to Chacal and he'll get you what you need.

 

Agreed... Got parts on the way, will tear into it as soon as everything arrives.

Would I have to mess with the bottom end gasket (jugs to crank case) throughout the process, or would it be OK as long as I don't disturb it?

 

The base gasket will be fine if left in place.

 

Should be fine if left in place. As long as it's not disturbed. The cylinders only have one separate fastener of their own, otherwise they're the meat in the head/cylinder/crankcase sandwich with the head bolts. Just be careful there isn't too much medieval honking about on things when you pop the head off and it will be fine.

On reassembly, pay close attention to the head bolts/nuts. The two on the outside/right have copper sealing washers under them, not standard washers. The galleries those two outer head bolts are in are the oil feed to the head (which is why it's seeping where it is.)

 

Good to know! I will have to be uber-careful popping the head off the cylinders. I did order a fresh set of dowel pins and seals from Chacal, along with new copper washers. New head gasket is inbound from the local UJM shop. Also have a place to take the head to if it needs a shave.

Other than this stupid leak, the bike runs great, so hopefully I won't open another can of worms in the process. Fingers crossed.. 8O

 

Um... I just discovered something. Copper washers installed under bolts between #2 and cam chain gallery... NOT on the outside, to the right of #4.
WHAT HAST THOU DONE, PO

 

Lovely. Not only do the copper washers seal their locations, they allow the aforementioned "sandwich" to mash together nicely around those bolts and seal the galleries.

Anyway...

You might want to think about cleaning up the valves and replacing the 34 year old valve stem seals while it's all apart. I would.

And be sure to keep track of which valve bucket comes out of which hole.

Do you have a factory book? The Haynes leaves things out.

 

Haynes is what I have.. What am I missing?

 

Documenting everything might take a minute.

If you're not in a hurry, I can compare the two and shoot you some scans of the pertinent stuff from the factory 650 book. PM me with your email address; and be patient.

 

Oh, I have the time! Been waiting 5 years to ride this thing. Sending PM! Thank you, Fitz!

 

ARGH!..

So I got the head off. Disassembly went perfectly smooth. Upon further inspection, I discovered a couple of things:

a) One of the locating dowels between the head and the jugs was absent.
b) One of the remaining three dowels was rusted all to s**t.. And it happened to be one in the front oil passage on the right side.
c) The cam bearing caps were all mixed up. I1 was switched with I3, and rotated 180 degrees. Same for E1 and E3. So, whoever worked on the mill before me, obviously didn't follow a manual of any kind.

Soooo... Here is the big question. Do I keep the cam bearing caps oriented the "wrong" way, since they may have had some potential mileage put on them that way? Or do I re-assemble properly? I don't see any galling on the bearing surfaces.

There are some very light scratch marks on the head-to-jugs mating surface. No deep scratches. Should I send the head off to get it leveled?

P.S. Thank you, Chacal, for recommending that I get a set of dowels.. I'll obviously need them

 

i'd put it back like it was.
there's a spec in the book for head warpage, 10 thou in my book, thats quite a bit. but a warp and a scratch are different a light scratch shouldn't hurt anything depending where it goes. oil hole to nowhere or another oil hole, no problem. oil hole to outside, then maybe gasket goo it.

 

So, I think I have officially determined the reason for the oil leak.

All three seals look like that. Pretty sure they came from a faucet repair kit. This dowel pin is the worst of the bunch, but others aren't far behind..
New parts on the right, for comparison.

:|