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waruta 11-16-2012 10:29 PM

2003 LC4 SM KTM Owner, a few puzzles...
Hi all,
I've recently purchased a 2003 LC4 640 SuperPrestige and am trying to sort out some issues, but am having not much luck. I'm based in Japan and although we do have some decent KTM shops here, they usually charge out the wazoo just to look at the bike, so I wanted to diagnose any issues before having them take a look.

1) When I start the engine using the e-start, sometimes I heard two or three loud "clacks" or "clunks", this also happens when I start the engine after a short shutoff period and restart when the engine is hot. (Like after a short shopping run, pop in and pop out of the store). Is this normal or is it a sign of a more serious engine issue about to happen?

*UPDATE: read through this: and am REALLY, REALLY hoping this is not the problem but it sounds like it is....jeez. Going to try and hit up the local KTM guys for the correct seal or find SKF Seal # 19993 on the 'net here.

2) The brake light doesn't brighten when I pull the front or the rear brake. I looked at the bulb, one of the contacts was looking pretty bad, so I replaced the bulb, but still not working. The bulb lights up no problem along with the blinkers and the headlights, but I cannot fathom why it won't brighten when pulling on the brakes. Besides being a safety issue (not wanting to get rear-ended), I also don't want a ticket....

3) Stalling like crazy. Maybe it's because I am more used to riding 4-stroke 250's and 1200 cc streetbikes before I got this thumper, I am always expecting it to pull away in low revs with no problem, but the engine will cut out. I have read through this thread: and have gleaned that all I have to do is cut the clutch switch wires, solder them together and tuck it under the triple correct? I'm assuming the same goes for the side-stand switch. (cut, solder, tuck it away).

Thank you for reading and any help would be much appreciated.



SRG 11-17-2012 07:25 AM

There's allot to read here :

On issue 1 - sounds like the decompression system doing it's job to me. The clacking sound at low idle (too low - may be part of your stalling issue) and shut down is totally normal. Idle speed should be 1800 rpm or so which will keep the decompression system from kicking in.

The rear lights on these bikes suffer from vibration issues. It's hard on the contacts and filaments. Try another bulb, make sure the contacts are getting good/firm contact, get a couple of spare bulbs, don't buy cheaply made bulbs.

gunnerbuck 11-17-2012 09:00 AM

When both your front and rear brakes do not trigger the brake lamp then to me it would suggest a wiring or contact issue.... I would check the wires to the lamp that sandwich between the rear fender for breaks or shorts... Like SRG mentioned, vibration has a tendency to kill bulbs and over time kill the bulb socket holder... Check the contacts on the bulb socket with a tester to see if power is getting to them when the brake is applied... On one of my 640s on tour, the brake lamp quit working because of a deformed {from vibration} bulb contact... For a temporary fix I was able to get it working again by prying it up a bit and scratching a better point of contact with a knife...

Manakau.KTM 11-17-2012 12:36 PM

I have a 02 640e and have had a similar problem with the brake light. I
noticed that both filaments were going and traced it to the switch on the hand brake. it had popped out and for some reason the bulb becomes powered when that happens. While I thought that I had lost the brake lights, in fact they were working overtime. Also the rear light became really hot.

bmwktmbill 11-17-2012 05:37 PM

There is a drain screw on the carb bowl, open it and drain the bowl.
Replace the spark plug.
Tighten the plug wire into the cap before connecting.
Tighten the carb connection to the engine.

waruta 11-19-2012 01:38 AM

Thank you all for the replies. I have been working on the bike over the weekend and found out the following:

1) The engine clunking could be the decompression issue as I had the local KTM guy look it over and he said that the starter clutch going bad would happen more frequently if the bike was hot and usually ends up with the starter spinning and/or burning out. We tried a few times starting the bike when I got there and (of course) it made no sound at all when started multiple times. Anyways, I'll keep my eye on it just in case, and am ordering the SKF 19993 Seal as a backup when/if the starter goes.

2) The brake light problem was traced to the front Magura brake switch. It kept going through bulbs because the switch was constantly on, burning up both filaments at the same time as well as one of the bulb contacts. Some CRC-556 (WD-40 for you folks) and some dielectric grease on the contacts helped it out. Now I need to find a suitable LED replacement, although I am hoping the vibration won't bring about an early death to it as well.

3) Stalling seems to be better, have messed around with the idle a little and also ran some seafoam through the engine, seems to idle smoother now as well. I will be doing the spring/drill slide mod in the near future as well as rejetting for both the KTM race muffler and side airbox. I thought I might as well do it all at once instead of constantly rejetting/setting up the carb for every little mod.

Thanks again to everyone that replied, hopefully I can get it all set up perfect and keep having a blast on my first supermoto.



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