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Old 08-12-2014, 09:55 PM   #1
Snowman89 OP
Joined: May 2012
Oddometer: 7
KTM 640 that is making a strange engine noise after rebuild

I dont really know what to do with this bike anymore..
The bike is KTM 640 -00 with a -04 engine with the high flow cylinder head.
The reason for the rebuld was 2 leaking valves.
I had the all the bearings in the bottom of the engine changed by a KTM mechanic and he also rebalanced the crank.
Another company rebuilt the cylinder head for me.

I then assembled the whole engine according to KTM's repair manual, doing the opposite as when i was disassembling it.
The KTM mechanic also checked the con rod when he rebalanced the crank and it was fine.
The piston was measured at the workshop that did the cylinder head.

But even after the rebuild the engine is now making a rather big mettalic sound.
The sound seems to be there when the engine is cold and warm and seems to not follow RPM.

I tried capturing it with my camera, .
But its really hard to capture the sound with a camera..

Yesterday i removed both the clutch cover and the stator cover and i could not find anything out of the ordinary.
The oil and screens looked perfect to.
Any help or ideas would be very much appreciated since im completly out of ideas right now...
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Old 08-17-2014, 03:39 PM   #2
Snowman89 OP
Joined: May 2012
Oddometer: 7
Just wanted to update this thread in case someone else have the same problem.

I finally found the problem and it was one of the balance shaft bearings.
They were both new, but one of them still made a nasty sound :(
So i removed both bearings and the balacer
Now i have to chain my bike to the wall when its idling
Jokes aside it now runs great, i also had the crank balanced when i rebuilt it so it doesnt vibrate that bad actually.
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Old Yesterday, 12:27 PM   #3
viertaKTMotor *****
Joined: Nov 2010
Location: Poznan, Poland
Oddometer: 214
Excuse me Emil but what is that red goo on the cylinder base gasket and around the rocker cover? Looks like a plain, vinegar smell silicone for me... Why didn't You used some Loctite 518 or similar Honda Tribond recommended for this kind of application? Thin layer ist just enough to stop the leaks...
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