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Old 01-16-2015, 12:47 PM   #1
redprimo OP
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Help, Iv've got a head gasket leak on fresh rebuild

The bike in question is a freshly restored 1980 Honda xl500s. I rebuilt the top end with a Weisco 10.5:1 piston and not sure on the brand of gaskets but I usually prefer Japanese. I have a rather bad oil leak coming from between the cylinder and the head and it started, or rather I noticed it after a couple hundred miles, I might have noticed it sooner but I was tracking down some intermittent electrical problems in the first few shake down rides. I now have 1K miles on the bike and now when I park after a 25 mile ride it will leave one or two drops of oil on the ground, more if I haven't washed it in a while. I'm sure this doesn't qualify as a bad leak for most of you but I am not used to any oil leaks on engines after I rebuild them.

I have a manual and followed the torque sequence and specs and installed the gasket dry as per the manual. I'm, really bummed as I got a perfect silicone seal on the head cover and I'm not getting a drop from the valve covers, both of which are the known weak points and I will have to break both those seals to fix the leak. The one thing I did not do was to re-torque the head after running it a few times. It's a major PIA and requires pulling the engine and popping the head cover, the head to head cover gasket is silicone sealant.

I obviously did something wrong and I don't want to pull it apart and put it back together if I am likely to have the same leak again. I have had a long time owner of a bike with the same engine tell me he uses 220 sand paper on the patrs of the castings that make contact with the gaskets, sanding inline with the gasket to create micro groves that bite into the paper gasket to help it seal. I like this idea and understand the importance of keeping the sandpaper flat and the importance of cleaning the sanding swarf is rather obvious.

Any other ideas of where I went wrong or what I should do to keep the oil on the inside of the engine? also any thoughts on cleaning and re-using the paper gasket?
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Old 01-16-2015, 10:36 PM   #2
Walterxr650l
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Well I'm not a professional mechanic, but every engine that I have had the head off of, had a metal head gasket. My suggestion, if they are available, get an OEM head gasket and put that in.

Walter
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Old 01-16-2015, 10:57 PM   #3
keiji
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Do you know exactly where the leak is coming from? If not, clean off the engine and throw some baby powder at it.

I once thought I had a base gasket leak - turned out I was seeping from my cam chain tensioner gasket.
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Old 01-17-2015, 03:34 AM   #4
redprimo OP
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Quote:
Originally Posted by keiji View Post
Do you know exactly where the leak is coming from? If not, clean off the engine and throw some baby powder at it.

I once thought I had a base gasket leak - turned out I was seeping from my cam chain tensioner gasket.
It's definitely coming from between the cylinder and the head. As i think about it more I can't see how the head gasket could be leaking and now I'm starting to suspect that it' the rubber grommets that go on the metal tubes that connect the oil passages in the cylinder and the head. I ordered a different brand top end gasket set tonight.
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Old 01-17-2015, 03:43 AM   #5
redprimo OP
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Quote:
Originally Posted by Walterxr650l View Post
Well I'm not a professional mechanic, but every engine that I have had the head off of, had a metal head gasket. My suggestion, if they are available, get an OEM head gasket and put that in.

Walter
The bike is 34 years old and there are very few OEM parts available for this bike and a gasket set was not one of them.
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Old 01-17-2015, 04:54 AM   #6
Perthite
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try retorquing the head bolts?
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Old 01-17-2015, 07:06 AM   #7
keiji
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Quote:
Originally Posted by redprimo View Post
It's definitely coming from between the cylinder and the head. As i think about it more I can't see how the head gasket could be leaking and now I'm starting to suspect that it' the rubber grommets that go on the metal tubes that connect the oil passages in the cylinder and the head. I ordered a different brand top end gasket set tonight.

Does the leak align with where the oil passage is? Is the passage a pressurized passage, or is it just an oil return?
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Old 01-17-2015, 01:03 PM   #8
Beezer
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did you check the head and barrel for warp? you can check it with a straight edge but it's kinda tricky with a single cylinder because of the size. they usually give you no more than about .003", maybe less on smaller heads. when I do a head I always put it on my surface plate. you can use a sheet of glass instead but have something solid underneath. see if there is any rocking movement.... if so its pretty far off. the manual usually shows slipping a feeler gauge around the bottom looking for a gap. you can try that, but it is easier to just tape some 180 maybe 220 wet/dry sand paper to the surface, squirt it with WD40 & run the head on the surface. you don't need much pressure. do it in random motion. the scratch marks will be everywhere & even if the head is flat. if not, keep doing it until they are. same for the barrel
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Old 01-29-2015, 01:20 PM   #9
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Well I found the leak, a classic good news bad news scenario. so the good news is I found the source of the leak, a missing head nut between the exhaust ports, the one that attaches from under the head. The bad news is I discovered it while pulling the head after i siezed the engine. I'm really bummed because I only had 1,200 miles on a completely fresh top end.
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Old 01-29-2015, 03:23 PM   #10
Beezer
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aakkkkkk.... bummer...... and the cause of the seizure?
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