Head Gasket leak at Cam Chain tunnel ???

Skip

Hi All, just looking for some input.I have pulled the top end off my 650 to cure a oil burning issue at the LH cylinder.Compression was 130 psi on both cylinders cold.I was pleased how everything looked for cleanliness but the black carbon on both pistons and combustion chambers made it clear there was a problem.The cylinder head gasket was in what looked to be good shape but was wet with oil at the very inside center of both cylinders at the cam chain tunnel.There were no tears in the gasket and both the cylinder jug and the cylinder head were wet. Almost like it was sucking it in over the gasket. and it had been 3 months since the bike was last started.Any one got any opinions on this.I remember Retiredgentleman mentioning a similar problem. RG if you could update a fellow Canuck I would appriciate it.
Skip

Retiredgentleman

Skip;
Yes, that's the same problem I had. I had a ton of carbon on the pistons and heads. My head gasket was wet just as you mentioned. I believe it was due to the head studs not torqued down properly after the PO had the head and cylinders off.

jimmythetrucker · Full Member Joined: Mar 12, 2008 Posts: 1283

Don't these heads ever get "out of flat"? Which is to say: Don't these heads ever need milling?

Skip

Retiredgentleman, thanks for the reply and the photo.That pic could be the twin to mine.The LH cylinder was the one which was smoking,but there was almost the same amount of carbon on the RH.When I pulled the head off I was like "well there's my problem".Not often when working on machinery of any kind that your awnser is that obvious.Now a clean up.,some measurements, hone and rings,lap some valves. jimmy got me thinking so I'll check the surfaces with a straight edge, some bead blasting and things should be as they should.It has been a long,cold,snowy and icy winter here on the east coast so still lots of time yet.What stage of repair are you at with your motor RG.

Retiredgentleman

Skip;
I have the engine in my basement because the winters in Calgary are just too cold to work in the garage.

I have the engine all cleaned up, new valve seals, new front camchain guide,new camchain, new rings, valves lapped. Opened up the side cover for a clutch inspection and found it to be in good condition, but there was a missing washer, which I replaced. Also found a washer missing from the tach drive..............those PO's are not to be trusted!

I have the pistons installed into the cylinders. Some warmer weather coming in a few days, so I plan to move the engine back to my garage for installation of cylinders, heads, rockers covers etc.

Probably another 6 weeks of winter Shocked

, that should give me enough time to get the bike all together and running.

Skip

RG;
The only good thing about winter is it buys us time to go the slow and steady pace on general repairs and repair of those damm PO's mistakes! I may have waited a little long,you are on the home strech and getting to the fun part on putting Humpty Dumpty back to together again.
It should be a breeze for you finding netural this year after replacing the missing thrust washer on the clutch hub.I know on mine, I replaced all the discs and new washers and bearing a few years back and it was like a different bike altogether!

Retiredgentleman

It wasn't the thrust washer that was missing, it was the very first flat washer (shim) next to the shaft bearing. Actually my clutch had been working quite well. The missing washer was causing the clutch basket to rub on the crankcase.

Jake68 · 650Rider Supporter Joined: Mar 23, 2007 Posts: 841

This leak is a real XS650 little known problem scenario Smile

I had it (now solved)..

This is what I discovered...

The cylinder studs can STRETCH and ...not be sufficiently wound in? The later of which I am less certain.

This makes the acorn or dome nuts bottom out!!!..(revelation! LOL)

Anyhow..I cured this by using stainless steel washers (double thick) and then later I used open top nuts..(also double thickness) I had to have these made.

Now at last, no leaks and no smoking from cold.

Retiredgentleman

Jake68;
Back to this topic,we talked about before. Its likely a good idea to use the double nuts as you said. That's good that it cured the oil problem.

While doing the top end re-build, I have taken some careful measurements. I measured all the studs, and found one stud was not screwed in as far as the others. So, that stud would be the worst case. I found that in this worst case, the clearance inside the domed nut would be .219" with the stock rubberized washers. I plan to use 650central copper washers on the outer studs, which decreases the clearance to .166" ( stock washers are .124" and copper ones are .071"). I will be adding a metal washer to the copper washer to bring it back to equivalent of the stock washer.

It would appear that I have .219" clearance before the domed nut would bottom out. Now the gaskets will be compressed some and the studs may stretch some, but I don't believe that could use up that .219".

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