Monday, August 17, 2009

ride report

OK, a handful of scrambles up into the hills and around briones reservoir, and I've accumulated a little data. Butt dyno says it's pretty good. Got a bit of an oil leak around the cylinder head, left side. Now a little oil leak aint the end of the world and there are more than a few XL600's out there with the affliction...I prefer to think of an oil leak as affirmation of oil actually getting to that part of the insides, myself...would be awful lot worse if it weren't. Still, how much is too much? I notice little spatters of oil on my left boot after a ride, so it's obviously producing more than just a little bit. I'm guessing that black stuff is road soot as opposed to some sort of precipitate from the oil, which itself looked pretty clean to me:

Here's a closeup of my plug. I did a Wide Open Throttle run in an industrial area right near home, probably not long enough to truly test that fuel circuit but still here's what the plug looks like

And finally, that rubber interface between the carbs and the intake manifuld does get pretty hot, not sure how I feel about the fuel line draping across like that. There's a mechanic's joke from the North Woods about assessing something ambiguous yet critical like this, you're supposed to shrug and then say: "It's probably OK". But you're laughing because you know that's the same thing muttered by regretful space shuttle engineers, aircraft ground crew men, and any number of botched shade tree mechanics out there.


Here's a picture of the cylinder when I was doing the engine rebuild. I don't see how oil could be weeping out the left side of where the head makes contact...most likely oil coming from somewhere else...but where...


  1. If you don't apply a liquid sealant to the rocker box gasket, they all leak. You had already one that part before I heard of you. I usually spray it with some copper coat from an aerosol can on both sides, nice and sticky. Mine is currently leaking due to one stripped bolt, I'm going to try and thread it deeper and use a longer bolt with only the tank off at first. If it continues, I will have to pull the rocker box and do some heli-coils. Usually that means the whole engine as well, or at least dropping the mounting bolts to gain top-end clearance, but if I'm going to do all that, I'll get new rocker arms and a cam that is in spec, I've not changed those items out of this engine yet. Even with the leak, the oil consumption is lower than it's been just about ever, certainly much lower than before the recent top-end rebuild. Weird how you're getting oil on your boot as clean as your engine looks. I've been leaking a while now with no such occurrence. My front fender and the side of the cylinder and head are coated.

    Oh, and RE: the fuel line, don't worry about it. Have you any idea how hot the bottom of your gas tank gets? Look at the old stocker with the heat-reflective shielding. Mine doesn't have that nor do many tanks, but it doesn't stop your fuel from nearing 200 degrees while you're riding. True enough about the engineers in more serious professions than thumper customizing, to some extent anyway. We ARE indeed all human... except for some of us. :)

  2. Thanks for posting up...right you are about leaking rocker boxes...although I'm pretty sure my leak is coming from the next seal down, which is to say the gasket between the head and the cylinder. To me, that seems a bit more severe a place to have a leak than the rockerbox, right? Do you see leaks there? Maybe I'll post up on the XL600 thread of

    I suppose if I had a front fender, there would be oil spatters on it too...for now it's just my boot (!). You know, it's a lot like bleeding. If blood is getting on the floor, that's probably a bad cut: consider going inside for a bandage. if the blood's proximal to the wound, meh, prolly can just close it up with some super glue or tape.

    I found a source for that adhesive aluminum insulation stuff like what was on my stock tank (which I will be packing up this week to ship to OR) for my glass tank, just for some peace of mind. What I'd really like to do is weld up a stainless steel conduit for the fuel line, but you know how it goes...

  3. Even if you did weld up a conduit for your fuel line, it would still get hot in there. You're silly. Engine compartments of cars get upwards of 200 degrees and heat the fuel lines with it. The hot engines of cars conduct heat through the aluminum intake manifold and metal fuel line even more than your little rubber one resting on the rubber intake manifold. It is just the nature of engines to be hot and heat their fuel lines. Stop being silly.

    If you are leaking any from the rocker box for sure, chances are it is all coming from there. It takes a severe level of negligence to under-toque the head gasket badly enough to let it leak. Even if you had, you would be able to snug up the two external nuts and more than likely stop the leak. The head gasket can only leak on the side that there is oil running through it, which is the right side since that is where the cam chain goes through. I saw a photo that would indicate that oil is leaking on the right side. If this is the case, it is definitely NOT the head gasket. Besides, if it leaks enough to get oil coming outside the engine, chances are good that the compression would leak into the oil, leaving it contaminated with carbon that you would see. I've had a head gasket that leaked compression under load on this particular engine due to a sleeve that was not in it's proper position, and even that did not leak oil. I am using a fiber and metal composite aftermarket head gasket that is on it's third use and I even heard a small cracking noise when I flexed it and used it anyway with no leaks or problems. Again, stop being so silly.

  4. I just don't like the fuel line making direct contact with the intake is all. "It's probably fine" but it would be better to have the insulative powers of air surrounding it instead of making direct contact with the intake tract. Just being paranoid, not silly.

    And don't put severe negligence past this hamfisted wrencher...I vaguely recall those cylinder head bolts feeling like they would strip at any instant; probably went on the low end of the torque specs. I'll recheck for oil leaks around the rockerbox seal, but I would expect the oil to collect in the engine fins above the cyclinder head gasket seal, up to the rockerbox, right? Did not notice any...shrugs.

    I agree it's an unusal place for oil to weep out since the cam chain is on the other side. I updated the post above with a picture of what my cylinder looks like. I thnik those four big holes arranged around the cylinder access the studs taht actually hold the cylinder to the bottom end...I don't see any place for oil to travel but the cam chain tunnel...

  5. The other thing is that the position of the oil filler leaves dribbled oil in those places from filling it up and spilling some accidentally. You don't show very much on the head there, so if it stops that could be it. Meanwhile I'm battling a known rockerbox oil leak due to stripped threads. Gonna have to thread it deeper than I did today, if I thread it deep enough I may almost lose the tap, so I'll probably have to heli-coil instead. Bummer! I tried threading it deeper but it just wasn't enough threads to torque sufficiently without stripping.