'01 KTM MXC400 Seized Motor?????

[KTMster]

I took off on a ride Sunday & my bike totally locked itself up just like a bike does when it seizes. It wouldn't make sense that my bike is seized though because the oil is changed after almost every ride & I am not a trasher.

So far, the oil has been drained and there are no metal chips or anything in the oil, and the spark plug looks good.

I am totally confused & am wondering if anybody else has any insight.

 

[KiwiBird]

Bummer Darla! I don't know if the 400 was susceptible to the same malady as the 520 but... you might have dropped the cam bearing.

I'm sure one of the others will chime in with the procedure but pulling the top cover off the head will tell you if that is the cause.

 

[KTMster]

Kiwi, thanks for the input. It's times like this that I really wish I knew more about RFSs.

 

[ktmike55]

Cam bearings are suspect, chain somtimes breaks wads up in the bottom and stops the motor cold. Sorry hope this isn't the case

 

[KTMster]

Wow, my bike definitely stopped cold.....it threw me over the bars & I wasn't even going that fast.

Also, if the problem is that I either dropped the cam bearing or broke the chain, is this going to happen all over again once I get the problem fixed?

 

[biglou]

Bummer, Darla. I remember when you were looking to have this bike shipped to you (I think :think: ). Did some searches and came up with a few threads that may make for some informative reading. I think I have them listed here in order of relevance:

Click.

Click.

Click.

Click.

Click.

 

[jeb]

I don't recall hearing of a cam bearing failure causing the engine to lock up. Mine didn't, it just got real noisy all of a sudden and the WP seal started leaking.

Please let us know what you find. The busted cam chain idea makes a lot of sense to me. Hopefully it's nothing too serious.

 

[KTM-Lew]

I'm thinking the de-compression bolt fell out is hung in the chain? :think:

 

[TTR Dave]

KTMster: I had my 2001 400EXC grenade the cam bearing... it destroyed the ENTIRE motor. For whatever reason, KTM used a
Tawanese bearing only in the cam bearing?????? All the rest are the good German bearings. Now the good news.. KTM replaced the whole motor with a new one (BIG SMILE) For 2002 the bearing is now sealed and doesn't come apart. Good luck.

 

[ktmike55]

KTMster
If you were going slow it does less damage, I hope. There using a different bearings now. there is also a service bulliten on decopression nut. the one that replaces it is not poly lock. when you go through the top end update to 2002 parts. also check rocker rollors. Water pumps seals, spacers & bearings from the 02 fixes problem, sorry I hope damage is not to Bad

 

[scottyr]

When I had my 00 WR400F the timing chain skipped and locked the motor up solid. The entire motor was junk. Everything from the crank up had to be replaced. Lets hope that isnt what happened to yours.

 

[SFO]

My brougham FLEA, just found that his third decopressor bolt unwound and is tearing in to replacing another cam chain and decompressor bolt with a welded up fix up that no one else has experienced.
Forgive me, ktm's need nothing.

 

[KTMster]

Lou, thanks for the links. They were VERY helpful.

Thanks to everyone for all the helpful input & info. I finally dropped my bike off at the KTM dealership today since it doesn't look like it is going to be anything simple at this point in time.

I will post what the dealership finds as soon as they let me know--they said they should have it tore apart & diagnosed by Wednesday.

 

[flea]

I am with KTM lou on this one. My money is on the decompression stop bolt. There are so many places for the nut to go and "seize" (well stop) the motor. Good luck, be sure an post the actual facts!

 

[KTMster]

SFO: I don't fully understand your post, 3rd nut unwound?

Flea: I will definitely post the actual facts as soon as I get them.

How or where do you guys get these service bulletins so I know what to watch for in the future?

I have been contemplating buying an '02 400 or 520 while my bike is being fixed because I figure I can put my suspension on the new one. Is there ANY problems with the '02 400 or 520 that I should know about? If I do buy an '02 it will probably be the 520 so that Thom can have it when I get my bike back. Also, I am assuming that my '01 forks & shock will bolt right on to the '02. Does anybody know if there would be a problem with this?

Thanks!

 

[KTMster]

Oh yeah, if it turns out that the decompression nut fell out, I will still have them replace that cheap Tiwanese cam bearing with the '02 bearing while it's tore apart.

 

[SFO]

As flea could attest the third nut is not an aberant growth but the number of times this fastener has come undone on his bike.

 

[KTMster]

SFO: Would red Loc-Tite help cure this problem?

 

[SFO]

As flea is a design engineer I believe he has tried a few fixes.
Perhaps he will be so kinbd as to share them, or try pm'ing him.

 

[dstktmusa]

Originally posted by KTMster
SFO:
Also, I am assuming that my '01 forks & shock will bolt right on to the '02. Does anybody know if there would be a problem with this?

Thanks!

The SX 2002 models have 48mm forks where as your 2001 has 43mm, so bolting right up to an SX would require you to purchase the lower 3 clamp for the 43mm forks (the upper clamps are the same) The rear shock would bolt right up.

 

[flea]

My brougham FLEA, just found that his third decopressor bolt unwound and is tearing in to replacing another cam chain and decompressor bolt with a welded up fix up that no one else has experienced.

SFO is saying that the nut unscrewed from its bolt. This happens from the constant contact from the decompression centrifugal weight stopping on the head of the 5mm screw. Poor engineering solution because the nut always comes loose from the millions of hits no mater what locking compound you use. The last solution I tried was loctite and the updated screw. It fell out taking my intake valves with it
Prior to that I used a fancy aircraft spec distorted nut with SHCS with a nylon patch. It was loose but I caught it. Which was just luck.
My latest solution is to weld the end of the nut to the screw. However I use un-plated oversized nuts and socket heads cap screws. If you do this solution it might be better to use medium grade fasteners (rather than high grade like 12.9) as the welding heat might make it too hard. I don’t think that my problems are common. I suspect if I looked close enough around the hole I would see evidence where the loose screw head made the binding surface a little uneven

 

[KTM-Lew]

Any news??? :think:

 

[Bonehead]

Wow I just tore the valve cover off my 520 to change the cam bearings. The only reson I am doing this is because of all the posts about bad cam bearings and I just started getting seepage from the water pump seals. I got new bearings from ktm factory racing; they are ceramic roller bearings from Italy. Sealed one side. I can see no ware on anything, and I am pisst, that I tore the dam thing down. The only thing I can see that needs replaced is the water pump seals.

This is a 2000 520 that has been flogged to death. I change the oil after every 100 miles or every race.
There is not even any sign or ware on the cam gear. I run Dumonde oil, $8.50 per qt. Full synthetic, race gas and an electric fan. Fan runs the whole time at race pace.
The stock bearings were German.

 

[jeb]

Can you give more details on where you got the ceramic bearings?

 

[SFO]

Originally posted by jeb
Can you give more details on where you got the ceramic bearings?

http://www.rceracing.com/lowfriccerbe.html