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Trying to find a small oil leak in head.

Discussion in 'XJ Technical Chat' started by Ben Hinz, May 31, 2019.

  1. Ben Hinz

    Ben Hinz Member

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    I have a 1982 Maxim 650 that has a small oil leak in the head. From the pictures I have attached, the oil is pooling around the #2 cylinder spark plug and there is a coating of oil on the spark plug lead. The oil is only present in that area and finds its way onto the fins. When I first got it running, the leak was small enough that I could ignore it but seems to be getting worse. It is still only a few drips of oil accumulating over a few hours of riding. I have replaced the valve cover gasket which did not fix the issue. I suspect that the head might have a small crack somewhere that the oil is coming through. How might I be able to pinpoint the leak, and if it is a crack in the head, what should I do to repair it?
     

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  2. Chitwood

    Chitwood Well-Known Member

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    Did you replace the pressure washers on the bolts that hold the valve cover down? These are paramount to making that gasket seal properly. New gasket, new pressure washers, torque bolts to spec and my 650 hasn't leaked a drop since. I fully expect my 750 to respond the same when my parts arrive.
     
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  3. XJ550H

    XJ550H Well-Known Member Premium Member

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    ^+1 0n the donut replacment
    clean the area and dust it with talc you should see where the oil is coming from
     
  4. Ben Hinz

    Ben Hinz Member

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    I will try the talc powder and see if I can identify the source. Really hoping that i'm not dealing with a cracked head.
     
  5. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    You aren't.
    The valve cover gasket is the most common area for the engine to leak at.
    A crack in the upper part of the casting would be obvious.
    A crack in the lower part would put the oil in an entirely different location.
     
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  6. Ben Hinz

    Ben Hinz Member

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    I have now replaced the pressure washers to go with the new valve cover gasket. I torqued every bolt to spec but my leak has not gone away. In fact it has gotten worse. Before replacing the pressure washers, very little oil would leak during my commute. This morning, a significant amount was pooling by my spark plug and on the fins after a thorough cleaning. Any suggestions?
     
  7. Simmy

    Simmy Well-Known Member

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    I would remove the cover and make sure the gasket is seated properly in that area.
    It's easy to have it slightly off track in there.
    You could have some crud between the head and the gasket, only way to find out is to pull it back apart.
     
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  8. Ben Hinz

    Ben Hinz Member

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    Is there a recommended torque pattern/procedure? I just used a crossing pattern starting from the outside bolts and doing the inside bolts last. I first just got them all snug and then went around again and torqued to spec.
     
  9. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Inside, then outside. Otherwise you did right.
     
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  10. Ben Hinz

    Ben Hinz Member

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    Tonight I'll take the cover back off and check for any debris or if the gasket isn't on correctly. Then I'll put it back on starting with the inside bolts and report back in the morning after my commute to work.
     
  11. Chitwood

    Chitwood Well-Known Member

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    Before you take it back off, inspect the gasket along the mating surface. I was super careful, as always, when sneaking the valve cover on my 750 back in place but somehow when I snuggled it down part of the gasket rolled out of the groove and left me a nice little oil leak. I was able to loosen the cover up and gently persuade the gasket back into place, retighten, and so far so good but it honestly hasn't been run too much since I have to pull the carbs back off to remove orings and replace with correct throttle shaft seals.
     
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  12. Ben Hinz

    Ben Hinz Member

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    So before removing the valve cover last night, I thoroughly looked over the gasket and did not see any spots that appeared to be rolled over or not seated properly. After taking the valve cover off I cleaned all the oil off the gasket and mating surface. There wasn't really any debris on either the gasket or mating surface. I then reinstalled the valve cover and torqued down the bolts starting with the inside bolts. My leak has improved from yesterday but is still not fixed, after my 60 miles to and from work today I still have oil pooling in the same spots. I'm seriously considering just putting a tiny bead of black RTV on the gasket and calling it a day. I would try going up to 9 ftlbs on the bolts but I really don't want to strip the threads.
     
  13. XJ550H

    XJ550H Well-Known Member Premium Member

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  14. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Stripping the threads is an uncommon result when overtorquing the valve cover bolts.
    Usually the head cracks.

    100% of the clamping force for the gasket is provided by the rubber doughnuts on the bolts.
    The bolts just hold the doughnuts in place.
     
    Last edited: Jun 26, 2019
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  15. Polock

    Polock Well-Known Member

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    the valve cover bolts have a shoulder, 7ft/lbs gets the doughnut smashed and the shoulder touching. once the shoulder touches no amount of tightening will make it go down any farther. so don't do that
     
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  16. Ben Hinz

    Ben Hinz Member

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    Story Time: here is an update on my leaking head issue. Since my last post, I have taken my valve cover off two more times. Once to apply a small amount of Black RTV to the gasket (which had no effect) and another time to replace the gasket with another new one. My head is still leaking. I then began to think maybe the oil was coming from the nuts holding down the head so I took them off to find that someone had squirted red RTV all over the threads of the studs and underneath both the washers. Someone has tried to fix this leak before, to no avail. Keep in mind this bike sat in a barn untouched from 1993 to 2018 so this had been done quite a long time ago. Another thing to note is that the engine had a ton of baked on oil all over this same area when I got the bike. After a talking to Chacal a little, he told me that the only place oil could leak through the nuts was on cylinder 4, so gooping up those nuts and washers wasn't going to do anything. This week I thoroughly cleaned all of the oil off again with degreaser and let it dry. Then I ran the engine for a while without riding it hoping that I would be able to get enough oil to come out to really pin down the source. I found that the oil is coming from inside that higher air passage in the head directly in front of the cylinder 2 spark plug. All around the valve cover it was completely dry but when you look inside that air passage, the oil looks like its just seeping through the metal on the top. At first I thought that it might have just been residual oil that didn't get cleaned off so I wiped it off again making sure it was completely dry, ran the engine for a while and the oil came back. Still, there is absolutely no oil anywhere else but inside that air passage. I wiped it off again and sat and watched while I ran the engine, over 10 minutes a very small dark patch of oil began to form on the top surface of the air passage, seemingly like magic. There is no visible crack or obvious defect, but I think there is a patch of porosity or some sort of small casting defect in the head that has always been there and no one has been able to fix. I am going to try using some high temp JB weld epoxy putty and working it in to the top surface of the air passage. It might not necessarily be a permanent solution, but if the leak stops after that, then I at least know for sure where my leak is coming from.
     
  17. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Have we mentioned that the rubber doughnuts are what provides the clamping froce on the valve cover gasket? Have they been replaced?
    I'm not discounting the porosity idea, but that's pretty rare and would (or should) have been dealt with under warranty since it's not a problem that comes on suddenly (either the casting is porous to begin with, or it's not).
    Where you are describing the leak coming from is a common place for oil to end up when the doughnuts are hard, which causes the gasket to leak along the inner portion of the cover (near the cam tunnel) where it's harder to see.
     
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  18. Ben Hinz

    Ben Hinz Member

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    The rubber doughnuts were replaced at the end of June.
     
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  19. XJ550H

    XJ550H Well-Known Member Premium Member

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    sounds like someone removed head or at least the nuts.
    retorque or pull head and check work
     
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  20. a100man

    a100man Well-Known Member

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    I wonder if a compression check would reveal an anomaly on pot 2..
     

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