KTM 400/520 Safety Notice: Valvetrain

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EricGorr

Super Power AssClown
Aug 24, 2000
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KTM Safety Notice

As a proud owner of four KTM motorcycles it upsets me to write this letter to other “KTM Guys” because I feel the responsibility of informing people about a potential safety hazard with a motorcycle is that of the manufacturer and the management of the American importer/distributor. I don’t like playing the watchdog role but I’ve carefully examined several damaged motorcycles, ordered replacement parts, examined new parts, and performed repairs before I wrote this letter to inform KTM 400/520 owners of what I conclude as a potential hazard that can cause personal injury to the rider and or cost several hundred dollars to repair.

The valve springs on these motorcycles are prone to cracking on the bottom coil, which can cause a catastrophic valve train failure, and in the most extreme circumstance, enabling the valves to contact the piston causing the engine to stop abruptly. KTM has revised the spring design switching from a two-spring set to a single conical spring design.

Recently I ordered the new parts for a customer whose engine I am repairing. The new spring part number is 594.36.028.044 and it is relatively inexpensive. The problem is it doesn’t fit the new cylinder heads that KTM is shipping to customers. The recess for the spring seat in the cylinder head is approximately 2mm smaller than the bottom spring seat washer. And it isn’t apparent to the untrained observer so it is possible to install the new spring kit in the heads that KTM is currently shipping from parts stock, and onto older cylinder heads. The spring seat washer will soon fail causing the same valve train problem as the earlier two-spring design. I had to make a modification to the new head that I recently purchased from KTM that involved boring the spring seat recess in the head to a larger diameter. Not a problem for me, a performance machinist with a vertical mill and several boring tools, but a big problem for the average guy who expects that the parts will fit correctly. What’s worse is that there was no written communication in either parts box warning that the head would need to be modified to fit the new spring.

If you own a KTM 400 or 520 I suggest that you have your local dealer modify the head for the new conical valve springs and install the new parts with fresh stem seals. If you’ve been riding the bike for a few seasons it’s about time that the head was checked for routine maintenance like the condition of the valves, guides, seats and stem seals. If your engine fails there is no warranty or recall that I know of.

One final note, in September of 2002 I attended a national product liability conference at the University of Wisconsin/Madison and there were representatives from some American motorcycle manufacturers. One of the points covered concerned recalls and warnings. The theme expressed by the speakers was that honesty is the best policy. In my opinion profiting from a design flaw is inexcusable. In the near future I hope to see the management of KTM in America straighten out this debacle by sending technical communications to dealers and owners warning of this potential problem, labeling cylinder heads that require machining to accept the larger diameter spring seat washers or pull them from stock, and providing detailed instructions on exactly how to repair bikes that are currently in use.

Eric Gorr, a happy owner of a KTM 640 Adventure
 

SFO

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Feb 16, 2001
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Thanks Eric.
Could you post a sketch or the dimensions the base washer should be for this new spring?
Is there a new part# for a new base washer?
Does the '03 bike come equiped with this spring stock, and if it does the service manual say regarding seat pressure installed height service limits?
Or, they supply the spring with a new base washer that doesn't fit into the head counterbore?
There are some base washer counterboring tools available via goodson that will allow you to recut the clearance on this junction with a hand drill, but without a target installed height or seat pressure the home mechanic or uneducated dealer could make a serious butchery of this.
Great heads up, Thanks!
 
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dstktmusa

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Jan 5, 2001
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Eric,
Only the 2003 SX model RFS' have this conicle spring design in the cylinderhead. The EXC/MXC still use the "2 spring" set up. My parts book is clearly marked at the top of the page that the conicle springs are for the 450/525SX only. There is a seperate page for the EXC/MXC that shows the 2 piece design. There are also 3 different cylinderheads, one for the EXC/MXC 450/525, one for the 450/525SX and one for the 250 EXC -R. Make sure when you order replacement parts that you are ordering them for the correct application. As you stated the parts do not fit all cylinderheads.
 

dstktmusa

Member
Jan 5, 2001
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OK, I take that back. The 250EXC also has the conicle springs but they are a different part number. (for some reason I cant edit my post)
 

70 marlin

Mi. Trail Riders
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Aug 15, 2000
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Thanks again Mr Gorr! if I ever get that 400 I what so badly. I know where to ship it too!
 

Shaw520

Damn Yankees
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May 14, 2000
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Originally posted by EricGorr
KTM Safety Notice

 KTM has revised the spring design switching from a two-spring set to a single conical spring design.

 

Eric,  Thanks for the heads up. Can you give us an idea which years/models/ vin#s, ect that are equiped with the defected springs?  And what is the potential failure rate, (how many will experience the problem). Does the problem exist only on LC4's, or are all RFS's since 00' experiencing the same failures. Do you think the valve springs are cracking due to a defect in temperment, or binding, or whatever? Please keep us updated.  Sorry for the hundred questions, but this is the first I have heard of this, and between me and my riding buds, we have about eight RFS's, none of which have any problems.   Thanks Again
 

mike perry

Sponsoring Member
May 20, 2002
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Hi Eric-

SFO e-mailed me to have me take a look at this thread (Thank you very much)
I've kind of been waiting to see if there were going to be any problems brought up on this site relating to the KTM valve train. I've had a few discussions with folks here and abroad about spring and/or retainer failure. It was first brought to my attention at last years Industry show, and a local dealer here had 1 failure that I know of. Up until now it seemed like a few isolated incidents, so we haven't used the failures as a sales pitch.

About 6 months ago we did a dual spring kit for the KTM 400/520. It includes chrome silicon dual valve spring assemblies, Ti retainers, and hardened steel bases. The kit installs at about 75#, has about 205# @ .413 lift. (largest cam I know of- Grobewachter in Germany) and goes solid at about .500" lift from this set-up. (You guys could have found out all about this if you hadn't ditched me at the PRI show- I feel so cheap...)

A couple of additional notes- On our test head we only had about .410" from the bottom of the keepers to the top of the seal, so if you want to run more lift we make a shorter guide- standard and oversize OD's available. Also on our head I noticed that the exhaust seat stood proud of the chamber material-not good if the outer edge is exposed- maybe only in the first run of castings- but something to look for. By the time I had cleaned up the exhaust seat I had more stem protrusion than I could adjust for and had to make custom exhaust valves.

Finally, we also make standard and +1.00mm valves for these bikes.
 

BCR-Bob

Sponsoring Member
Mar 8, 2001
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I raced a LC4 620 for a couple years a did have valve spring failures two times. Once with the stock springs and again with R/D Springs, but the engine did have an aftermarket cam in it. I've owned and raced a 2000 520 since May of 2001 and so far have not had a spring failure. The head has been gone through once so far and needed new valves and seats.
I also would like to know if it would be possible to know what years or VINs have had this problem. If it applies to my model I would like to know so I could address it. Thanks
 

MrLuckey

Fire Marshall Ed
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Feb 9, 2000
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TTT

Just wondering if there was any more opinions/feedback/info on the topic. It seems like it could be very important for some of us.
 

Shaw520

Damn Yankees
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May 14, 2000
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Originally posted by TTRGuy
TTT

 It seems like it could be very important for some of us.

Uh, Yea,..I was kind,...a..... waitin on this one too... :flame:
 

emoney

Member
Mar 4, 2001
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I'm purchasing a 450SX, should I be concerned about this issue since it uses the new style valve spring design? Is there a fix or mod I can perform if there is concern?
 

mike perry

Sponsoring Member
May 20, 2002
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As SFO shows- you can e-mail me at work- mperry@blackdiamondvalves.com

I'll be back to you as soon as possible.

MP
 

BB420

Member
Jul 21, 2002
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EMONEY
CHECK OUT A POST ON TT (450/525SX PROBLEMS????)
The conical valve springs 59436028044 are for the 450/525sx only, the post at the beginning sounds like somebody is ordering the incorrect head.
 

emoney

Member
Mar 4, 2001
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Broke in my 450SX on Saturday, love the bike! Sat nite changed oil, installed Scott's filters, filled her up with 1250cc's of Silkolene Comp4SX 10/40 (revalved the forks/shock and installed Enzo subtanks while we were at it).
Sunday rode the bike for about 3-4 15min motos, on the last moto the motor went bad. Engine seemed to be "freewheeling", in gear but no compression braking at all. Tried to restart, seems to have compression, but doesn't sound right. You can kick it but you don't get that faint "thump, thump" from the exhaust. Kickstart gear doesn't sound right either. Will pull it apart this week and let you guys know. Any thoughts out there? Other wise the bike is fantastic especially with the MX-Tech suspension.
 

BB420

Member
Jul 21, 2002
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So, you have installed the 450exc springs and retainers in your 450sx????
The exc and sx springs/retainers are different. The sx springs are conical shaped and single, where as the exc are like last years, double standard type springs. I think what your going to find is that your intake valve spring retainer will be broken, possibly from contact with the rocker-arm. Check the face of the titanium valves to see how dished they are and also look at the valve stem above the retainer keepers to see how worn they are....
keep us posted
 

MrLuckey

Fire Marshall Ed
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Feb 9, 2000
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Ok now I am thoroughly confused. Are the stock springs a problem with the stock head on a 2002 400SX or not? I can't tell if you all are saying its only a problem on new heads with new springs or if its a problem with EXC springs used in a SX or even if its with the 400/525 or the 450/525
 

emoney

Member
Mar 4, 2001
16
0
OK, the verdict on the broken 450SX is...the valve adjusting bolt on the exhaust rocker arm broke off. The brokern portion then went down the timing chain shaft and caused the timing chain to then snap, which made contact with some hardware holding one of the plastic guides to break off taking a portion of the crankcase with it. Very ugly. Will require, new cases, rockers, valves, springs etc. This happened within 1.5 hours of use, so I'm going to make a warranty claim. KTM had better take a good look at this and fix it quickly.
 
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