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Noisy lc4 640 motor

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Hey guys, new to this site. I just picked up a 2001 lc4 640e with about 14,000 miles on it. The engine knocks like there is a bad bearing somewhere. Under load it appears to dissapate. I understand it has already had the updated bearing from ball to roller type installed under the clutch basket. I dropped the bike off at a local KTM dealer to check it out and to lower the suspension but wanted to make sure I have a good engine and not the skid plate causing the noise. Dealer told me today there is an internal problem and may be the cam bearings. Is this an exspensive repair? Thanks for your time.

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If it's the cam bearings, it's a cheap fix provided the cam isn't knackered....in which case it's expensive.

When my 620 had engine knocking badly, it turned out to be crank bearing which meant complete rebuild.

Hope you've got the simple problem of cam bearings only!

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My local ktm dealer changed out the cam bearings which he said were fine and checked the bearing behind the clutch and that turns out to be ok. He said it may need a crank rebuild. I'm starting to wonder if I brought it to the wrong shop:foul: I have a bad feeling :banana:

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Fitter: Did the dealer concur with your observations ?

IOW: What is the basis of noise estimate ? Do you know other LC4 owners in the area and calibrate your ears to others ? The LC4 is a noisey engine - Period.

...and under normal use and an acceptable level of maintenance many LC4s run well over 10K miles.

Do you know the history of the previous users maintenance regime ?

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The more I talk to people, it does appear these are noisy motors. Previous owner was also concerned and brought it to the local ktm dealer and was told that noise is normal for that engine.When dealer replaced cam bearing[only one was slightly worn and changed it anyway] he first drained oil and found no metal at all, which is a good thing. He told me to ride it for a spell and change the oil again to inspect for any signs of wear. If there is a problem I want to repair it before I take out the cases.

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So I'd apply the "If it isn't broke, don't fix it" caveat - UNLESS you can confirm (one way or the other) a suspect condition.

If the compression is good, the valves are properly adjusted and the oil looks good and everything else is hunky-dory, then... Well, it's probably okay.

You're in the right company (here) to receive the necessary feedback.

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The intake cam follower bearing is a comon problem for the LC4. You'll know you have it when you adjust your valves repeatedly and the motor sounds even worse than a bag of hammers falling down a spiral staircase. Loss of power too, especially if you roach the cam like I did. Smart to order them in advance and have 'em on the shelf so you can get right at it when the time comes.

G'luck. :banana:

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well if it is the crank bearing you will start hearing the knock louder.. mine had the dreaded blown crank bearing.. 30,000 mi 03 625sxc .. a quick cylinder pull will tell you if you have any side to side slop in the bearing or scoring of the wall .. It can get pricy if you dont catch it in time as the crank needs rebuilding and then a re shim possibly once the cases are mated..also the crank knock will trash the nikasil resulting in a re nik or sleeve or ... well you get the idea.. 14,000 is kinda short mi for a bad crank but you never know.. has your mechanic used a stethiscope on it? Do you have any friends that are decent mechanics that could help you through this instead of a dealer?

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The problem is the deadler I took it to just sold a new ktm to the previous owner and does not want to get in the middle of a pissing contest and commit to anything. I just want to know if there is a problem and fix it before the engine explodes. The service manager that I took the bike to get an inspection sticker said not to worry as these modles rap like hell, even though they only sell jap bikes. Still not satisfied, does not sound right to me.

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So i recently got a 2000 lc4 640 with 10,000 miles. I was on the trail and had to lay the bike over. It tipped slightly upside down while the engine was running for about 2 seconds. After i started it up agian it started making a thumping noise. Later did i find that oil had leaked out. I put more oil in and still makes noise. Is this the same problem people are saying on this thread? Thanks

Rory

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