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Old 02-08-2015, 07:43 PM   #1
lagfish OP
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KTM engine seized?

So I was riding along in my 2008 450 XC-F the other day, after about 30 min, the engine became suddenly very loud. Then when I rolled up to a red light, the engine completely died and would not turn over when I tried to start it. I also tried putting it into gear and pushing it to turn over the engine, but it wouldn't budge. Today, I took the valve covers off and noticed the exhaust valve was in the open position. When I loosened the camshaft bearing supports, then engine was able to turn over again.

Does this sound like the exhaust valve did not have any gap and might have hit the piston? Is that even possible on a KTM? Is there some sort of decompression mechanism that broke?

I took off the head completely and the engine turns over fine and there doesn't appear to be any scratches on the cylinder wall.
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Old 02-09-2015, 04:52 AM   #2
trailer Rails
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Sounds like a seized cam bearing.
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Old 02-09-2015, 09:27 AM   #3
lagfish OP
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Originally Posted by trailer Rails View Post
Sounds like a seized cam bearing.
Would that cause the engine to run but sound funny?
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Old 02-09-2015, 09:34 AM   #4
HellSickle
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Quote:
Originally Posted by lagfish View Post
So I was riding along in my 2008 450 XC-F the other day, after about 30 min, the engine became suddenly very loud. Then when I rolled up to a red light, the engine completely died and would not turn over when I tried to start it. I also tried putting it into gear and pushing it to turn over the engine, but it wouldn't budge. Today, I took the valve covers off and noticed the exhaust valve was in the open position. When I loosened the camshaft bearing supports, then engine was able to turn over again.

Does this sound like the exhaust valve did not have any gap and might have hit the piston? Is that even possible on a KTM? Is there some sort of decompression mechanism that broke?

I took off the head completely and the engine turns over fine and there doesn't appear to be any scratches on the cylinder wall.
No gap on an exhaust valve will burn the valve, not jam the engine.

Sound to me like your timing chain slipped, causing valves to hit the piston. It's not going to be pretty when you pull the head.
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Old 02-09-2015, 10:33 AM   #5
trailer Rails
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Quote:
Originally Posted by lagfish View Post
Would that cause the engine to run but sound funny?
I don't know. I am going off the statement that the engine locked up but when you loosened the cam shaft bearing supports, you were then able to move the engine.

The other post could be correct but it is difficult for that to happen while the engine is running, it is more likely to happen during startup when oil pressure is low.
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Old 02-09-2015, 02:20 PM   #6
dezrat57
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maybe valve spring broke, dropping the valve and piston impacting valve causing the valve to bend in the down position and keeing the piston from coming back up to TDC

dave
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Old 02-09-2015, 02:23 PM   #7
dezrat57
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maybe valve spring broke, dropping the valve and piston impacting valve causing the valve to bend in the down position and keeing the piston from coming back up to TDC
i have the same bike

dave
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Old 02-09-2015, 05:46 PM   #8
mpatch
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Quote:
Originally Posted by HellSickle View Post
No gap on an exhaust valve will burn the valve, not jam the engine.

Sound to me like your timing chain slipped, causing valves to hit the piston. It's not going to be pretty when you pull the head.
Need to know how long it sounded bad before dying and locking up. If it ran for a min or two before locking up I would think it wasn't the cam chain because normally when they go youll get a bunch of racket for a few seconds then it's game over.

misread hellsickles post I thought he said broke not slipped but slipped would make sense
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Old 02-09-2015, 06:33 PM   #9
lagfish OP
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It sounded weird (louder) for maybe about a minute for dying. It still had power when the noise was weird. I think it only died when I was stopped because my clutch drags ever so slightly even when I pull the clutch lever in.

I took some pictures of the head. Everything looks normal to me and the camshaft bearings can rotate freely. No observable damage on the piston either

http://i.imgur.com/KCJ1oEw.jpg
http://i.imgur.com/uELtGhU.jpg
http://i.imgur.com/0CS9ZaZ.jpg
http://i.imgur.com/C6vVoWC.jpg



All four valves can be pushed down by hand and feels OK.

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Old 02-09-2015, 06:40 PM   #10
trailer Rails
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You did not waste any time in yanking that thing apart.

Looks like a pretty much new engine to me.
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Old 02-09-2015, 06:49 PM   #11
lagfish OP
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Originally Posted by trailer Rails View Post
You did not waste any time in yanking that thing apart.

Looks like a pretty much new engine to me.
We'll see if I can put it back together

Is it worth it to rebuild the engine while I have it apart? I'm the third owner of this bike and no idea the #hours on it.
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Old 02-09-2015, 10:12 PM   #12
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I can't believe you are riding a twin-cam on the street. These don't last that long.

The cam bearing look fine.

Do I see marks on one exhaust valve? Was it hitting the piston? Does the piston have marks? Check that valve for leakage. Put some thin solvent in the head and see if it leaks through.

Was the valve timing ok when you pulled it down?

Check the oil pressure a lot on this bike. The plastic oil pump part wear and need to be re-toleranced.
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Old 02-10-2015, 07:49 AM   #13
HellSickle
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Quote:
Originally Posted by lagfish View Post
We'll see if I can put it back together

Is it worth it to rebuild the engine while I have it apart? I'm the third owner of this bike and no idea the #hours on it.
Great pictures. Puzzling. Good news, doesn't appear to be a top end issue.

Questions: Can the engine now rotate? How does the bore look?

If the bore is good, you'll have to keep working your way down. Any play in the crank? If not, the noise is likely from something loose in your bottom end. If you are the third owner, there is always the chance that something has come loose and is jamming in the lower end moving parts. Someone may have dropped a shim into the bottom end and not bothered to remove it.

I am the third owner of an '06 RFS 450. I did a complete top end last year. Your engine is different, and I'm not as familiar with the issues of the '08. I had heard of issues with seals between the crankcase and transmission failing, but couldn't tell you all the symptoms to look for. It was the first year of the new motor and there are known issues and fixes you might want to implement while you are in there.
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Old 02-10-2015, 08:08 AM   #14
Texasclouds
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bolt it back up, see if it runs, then jump it. in the air you should be able to listen for funny noises whilst red-lining her.
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Old 02-10-2015, 07:13 PM   #15
lagfish OP
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OK so I took a picture of the piston today and it looked like the valves were indeed hitting it - all four of them. Can you guys confirm?

http://i.imgur.com/1nrc63m.jpg
http://i.imgur.com/lVLhG6i.jpg

Piston wall looks pretty good though right?

By the way the water on the piston is most likely from when I did not drain the coolant completely while taking off the head.
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