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Old 12-20-2014, 04:13 PM   #1
plucky71 OP
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What's causing discoloration inside cylinder head?

I'm Resealing my KTM LC4 rocker cover. I Just pulled it apart and noticed an obvious dis colored area adjacent to the left side exhaust valve. Anyone know what is causing it and if it's a problem?
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Old 12-20-2014, 04:16 PM   #2
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?
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Old 12-20-2014, 04:19 PM   #3
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Old 12-20-2014, 04:20 PM   #4
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time for a valve job? kinda looks like combustion byproduct sneaking past the valve
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Old 12-20-2014, 04:21 PM   #5
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^ What he said.
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Old 12-20-2014, 04:26 PM   #6
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Perform a leak down test. That will let you know the condition of the rings and valves.
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87 Harley FXRS-SP ~ 06 KTM 625 SMC ~ 72 Honda CB750/915cc ~ 92 XR600/654cc ~ 95 XR650l/675cc ~ 03 CRF450r ~ 05 CRF450x ~ 02 XR650l/675cc ~ 86 YZ490 ~ 93 YZ80 ~ 93 XR650l Project
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Old 12-20-2014, 04:27 PM   #7
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ya, do that with the rocker cover off. it'd be obvious if air is sneaking past the valve
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Old 12-20-2014, 04:38 PM   #8
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It would be more evident coming out the exhaust port. Pull the header and spray some soapy water in the port. If it bubbles the valve(s) is leaking. Also listen to the case breather hose end (rings).
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Old 12-20-2014, 04:45 PM   #9
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Thanks guys.
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Old 12-20-2014, 05:03 PM   #10
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From the rocker pad wear on the left and little to none on the right, id say It looks like teh left side valve was tight (held cracked open)

So...don't be puzzled if there is no leak when you put it back together.

Left side is the auto decomp side correct? Maybe its sticking or something if the valves are/were clearanced properly.


Just curious, are those the stock valve spring caps?
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Old 12-20-2014, 05:07 PM   #11
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As far as I know, they are stock. I'm The Third owner.
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Old 12-20-2014, 08:20 PM   #12
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looks more like oil oxidized from heat to me. question would be why, and
a valve thats out of adjustment may be it. the valve sheds heat when it's on the seat. the tighter the valve clearance is, the less time it spends closed & the hotter it will run. the excess heat on the valve head has to go somewhere.... and one place is up the stem.

looking at where the discoloration is, all I can think of is that area gets less splash oil (for cooling) than the other side of the keeper. what is on there is getting cooked. thinking this because it looks like the upper spring seats are aluminum & alu doesn't change color like ferrous alloys.

Beezer screwed with this post 12-20-2014 at 08:26 PM
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Old 12-21-2014, 04:34 AM   #13
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Another pic
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Old 12-21-2014, 04:39 AM   #14
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Old 12-21-2014, 04:53 AM   #15
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Quote:
Originally Posted by Idle
Left side is the auto decomp side correct? Maybe its sticking or something if the valves are/were clearanced properly.
Both exhaust valves are moved with both decompressors, h-shaped rocker arms...

Dosnt look heat related, more like stuff slowly dripping back from breather tube and tainting rough surface?
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