1989 KTM 350MX/EXC

Discussion in '2 smokers' started by Ajacklee4, Feb 13, 2021.

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  1. sparkingdogg

    sparkingdogg Prisoner In Disguise

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    I had a DXC 600 about the same era, it looked just about like yours. I believe the DXC was also commonly called the GS back then. It has a speedo and light so it's either a DXC or EXC, the MXC would not have lighting or speedo.

    DXC = desert
    EXC = enduro
    MXC = motocross

    (at least going from memory)

    I don't believe there was an EGS (dual sport) in that era, but I could be wrong. But every KTM 2 stroke I have ever had has been a blast to ride, except the 600 2T, which was too hard to kick over. Once running it was a beast. EXC 300 2T has been one of my favorites, the 350 2T should be lots of fun, good torque and good top end. My EXC 300 was super easy to start. Good luck, have fun!
    #21
  2. PSchrauber

    PSchrauber Long timer

    Joined:
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    Location:
    Summer: Kemiö, Finland; Winter: North Germany
    I have a 1989 500 2T with road registration, back then we called the Enduros GS (for Geländesport) and the Moto Cross models MX (for Motocross).
    The 350's where the GS used vor Enduor here only a handful 500cc GS variant where made due to our noise and environment laws we had already then.

    Anyway the 350 and 500cc are nice bikes with, not very easy to use and the engines are difficult in their behavior.

    Today due to the banrupty of KTM inbetween the spare part situation is not good, there is nearly nothing available from the company,
    be aware to pay a lot for new parts which might still are on the shelf of motorcycle dealers from back then.

    To the ignition:
    The ignition is SEM and can cause trouble.
    The problem is not as previously stated corroded wirings instead electronical parts that are cast inside the plastic and don't tolerate that treatment as with each heat cycle these units expands and that is limited by the incast. Thus this Swedish SEM and also the Spanish MOTOPLAT ignitions of that era fail so often and easy even if these haven't been exposed to humidity. There are replacements form Electrexword and Powerdynamo around.

    Gears:
    The MX versions have just 4 gears while the Enduros have 5 gears, the 5'th gear which is actually the first can be mounted later.

    Clutch:
    The outer clutch case is fragile at least for the 500, there have been replacement clutch baskets around (Talon) which where inforced.

    Watercooling:
    Biggest problem are the casings ahich are made out of magnesium and not tolerant to the liquid of the cooling, later versions of the side cases had less magnesium and did not corrod so easy, there has been also alumium cases around but I don't know if you still can get any. Run coolant without water. Likely the radiators can have an issue with corrosion.

    Exhaust:
    The sixdays version had a nice triple exhaust (with pipe mid exhaust and rear end exhaust) and that is what you try too look up for best performance and lowest noise level.

    Plastic:
    Not available anymore and DC Plastics is not of good quality flimsy and geometrical incorrect.

    Piston / Con-rod / Cylinder:
    Not available anymore, I have mine from Woessner who did custom con-rod, and piston, as mine is a 500 it was already back then resleeved to 501cc to match wih the 500 -750cc bike class we had back then, thus by using an iron sleeve not a coated cylinder.

    Usage:
    Beside desert cross and Enduro riding is only a good idea if you have the 5 gear gearbox. What is slos fun is to have a second pair of wheels with 17'' wheels for super mortard, here the 350 and 500 are quite nice to ride.

    My bike which is still in rebuild a many years ongoing project:

    [​IMG]

    [​IMG]
    #22
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  3. Blazz

    Blazz Stationary Traveller

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    It's going to be a nice one :thumb

    Got to agree about the GSes. They surely had different exhalusts. On later models (1990+) they also had steel subframes while EXCs had aluminium (pre 1990 not so much as they all had steel subframes ; )

    In user's manuals /parts fiches there definitely was a distinction between 3 models: MX, EXC and GS's - even in late eighties)

    Interesting thoughts on the ignition. Surely the design with plastik casing was a poor one. The guys that rewinded a couple of those stators for me seemed pretty sure however that moisture is a culprit for failure on those. They said that once it gets into the casting via the steel plates of the coils + multiple heat/expand/cooldown/shrink sessions = busted stator.

    Do You have any experience with electrex substitutes- I plan to replace the K11 enduro SEM ignition I have on my 1992 MX. The original Digital control SEM unit I had on this bike was incomplete so I installed the enduro version. I have seen somewhere that electrex produces the ignitions for motocrossers with small "inside" flywheel- wonder how they perform?

    Anyway - good luck finishing Your 500 project - looks great so far :)
    #23
  4. PSchrauber

    PSchrauber Long timer

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    I have other bijes that have tbese incast ignitions from Motoplat too.
    The fix was the same as to the SEM, you carfully open the plastic and in surgery manner remove the old ekectronics oarts that have faild (mostly transistors) and reolace them with new ones and then use kind of JB Weld to recast the hollow.

    To Electrex world ignition I have no idea, I rely on repaired electronic ignitions and have done some swapps from point to electronuc ignitions from Czech Vape.

    These where too sold under the brandname Powerdynamo ignitions and these have an generator for lights included also a better manual as I have heard, but much more expensive.

    Anyway you might check Electrex World out. or get the SEM repaired.
    The reoair was 70 Euro and I think that is much effective solution.

    I never had an issue with the repaired ignitions so far.
    #24
  5. Blazz

    Blazz Stationary Traveller

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    Yeah, Thanks for the tip.

    That is however what I was doping anyway (get the failed SEM stators repaired as I wasn’t sure about the bike’s “behavior” on aftermarket ignition curves so decided to keep the stock one ;)

    Sadly once I had an issue with repaired one on ‘91 four stroke. The bike suddenly lost spark:( Brought the stator to the fellas that repaired this, and specialize in “antique” SEM ignitions- and they were pretty convenient that failure of their repair was caused by poor insulation of ignition cover and moisture that caused corrosion in repaired coils that led to expansion of the element and it’s destruction. They opened it again, rewinded the coils again an it works ever since…
    #25
  6. Foot dragger

    Foot dragger singletracker

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    KTM has made a 500 2 stroke,a 495 2 stroke,a 540 2 stroke,but they never made a 600 2 stroke. Would be cool if they did though!
    #26
  7. Blazz

    Blazz Stationary Traveller

    Joined:
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    I believe sparkingdogg had a lc4 600 (liquid cooled 4 stroke) that was offered since 1988 (an debuted in 1987 with 350cc and 593cc 4 stroke engines) also was available in DXC version I believe.

    [​IMG]

    but this thread is not a place for a thumper is it ? ;)

    With 2 strokes they went “only” as far as 540cc

    Anyway- working some fun “rally” conversion of ‘88 250 Exc/EGS now with my buddy

    [​IMG]

    … by the way- this one has healthy ignition, was standing in shed for at least ten years and fired right up after cleaning the carb and air filter. Good compression as well…

    they used mostly 350cc 2t and 4t LC4 for rallying in Incas these days but, oh well ;)
    #27
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