KTM 620RXC...Anyone??

Discussion in 'Thumpers' started by mbmt, Oct 15, 2009.

  1. Adios Pantalones

    Adios Pantalones AdventureDeficitDisorder

    Joined:
    May 12, 2005
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    2,330
    Location:
    San Diego, not Mex, but I can smell it from here.
    Thanks to all the good info here, some all the way back to 06 in a Gaspipe post,

    I ditched the old edelbrock and coughed up for a new FCR 41. :evil

    Long story short... it's a new bike.

    96, 620, kick only. 5000mi on it. It went from an good, old used bike that ran kinda crappy to the beast it should be.
    I can stop shopping for the replacement bike!

    Sudco set it up right and got it to me in 2 days. I am officially ready for desert season! :clap
  2. rz35027

    rz35027 Been here awhile

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    Vancouver BC
    Setup that undersprung suspension (if it's still stock) and all of a sudden it will transform again...
  3. Adios Pantalones

    Adios Pantalones AdventureDeficitDisorder

    Joined:
    May 12, 2005
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    2,330
    Location:
    San Diego, not Mex, but I can smell it from here.
    Yeah, still stock, Marz/Ohlin. Suggestions? :ear
  4. Adios Pantalones

    Adios Pantalones AdventureDeficitDisorder

    Joined:
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    Location:
    San Diego, not Mex, but I can smell it from here.
    Did a pretty good soil sampling last weekend, cracked the orig. front fender and brace. No OEM available.

    Any ideas on good fittting aftermarket fender? :ear
  5. katumo_jtb

    katumo_jtb bogus journeyer

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    OEM fenders from later year KTM's will fit. The bolt pattern is the same, you just need to make sure you get a fender with the "nubs" that hold the mask in place. I'm using a fender from an '04 625 on my '95.

    John
  6. Adios Pantalones

    Adios Pantalones AdventureDeficitDisorder

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    San Diego, not Mex, but I can smell it from here.
    Awesome, thank you.
  7. 2wheelwilli

    2wheelwilli n00b

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    Roanoke Rapids NC
    Ok i need rxc help, mine is a 1995 rxc620 kick only, i need to find a battery where can i get one, my speedo stoped working so im useing my GPS till i find one... this bike is a blast.....
  8. mik-ktm400rxc

    mik-ktm400rxc 4-stroke nOOb

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    I have a mystery starting issue on a ktm rxc 400 96'.

    I changed the water pump seals on my bike and set the valve lash gap to the specified .1 mm on my way out. I had the cylinder and head rebuilt last summer and decided the recently ground valves should be re-gapped cus' of em settlin' into the re-ground seats, theoretically. It seemed the valve-lash was too tight.

    Now.... it won't start. It has spark. I didn't mess with the carb. IDK WTF.

    I have tried tightening and loosening the valve lash to various degress without success. It won't even backfire. There is nothing at all happening when I kick it, no hesitation, no nothing.

    I don't know what I coulda done while I was in there. Could I have messed with the valve timing/spark timing when putting the head back on? I had to move the wheel a bit to get the water pump back on... That's my guess. Could it be sparking on the wrong stroke or at the wrong time? How would I check it? Correct it?

    Gracias amigos para su tiempo, everyone on here has been a huge help in the past and I look forward to your diagnosticating regarding this matter.
  9. katumo_jtb

    katumo_jtb bogus journeyer

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    The recent changes were timing gear and valve lash, so it's probably one of those, as you said.

    Are you sure you adjusted the valves at TDC on the compression stroke? You can lock the engine at TDC with the crankshaft bolt on the underside of the case. Also do you have auto-decompression? Are you sure the auto-decomp was down when you measured the exhaust valves? Also, I thought the spec was .15mm, not .1mm. However, I'd guess you're further out of spec than that, if that's the problem, but you should definitely make sure.

    The valve timing is the other possibility. If it were off, it would make valve adjustment confusing as the cam could be in the wrong place at TDC. Unfortunately the only way to tell is to take off the head cover and look. It's pretty easy to tell if it's off. Lock the engine at TDC with the crankshaft bolt and see if the dot on the timing wheel is even with the edge of the head.

    Good luck!
  10. mik-ktm400rxc

    mik-ktm400rxc 4-stroke nOOb

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    That's what I was thinking. Would this also throw the timing for the spark off? So that it would be sparking during the stroke or some other innapropriate time?
  11. katumo_jtb

    katumo_jtb bogus journeyer

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    The timing gear being off wouldn't throw off spark timing as the spark happens relative to the crankshaft position, which hasn't changed; the sensor for spark timing is in the stator cover. But it would cause the valves to open and close at the wrong time relative to spark and compression, which would make it tough to start.
  12. mik-ktm400rxc

    mik-ktm400rxc 4-stroke nOOb

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    I have the auto-decomp. I set the lash with-out messing with the decomp-cable, as the cable is attached to the valve adjustment cover, which was off to set the lash. I shouldn't need to do anything beyond removing the cable?

    Also, I didn't mess with the timing gear (I think) I just pulled the cover off the head and replaced the water pump. But when I replaced the water pump I had to move the back-wheel, and therefor the timing gear, to re-install it. I thought I kept everything in the same orientation as before, but am uncertain if I did. So the deal with that is i am worried I turned the timing gear around once before reinstalling the valve/head cover, and if that could affect things....
  13. katumo_jtb

    katumo_jtb bogus journeyer

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    OK, I misunderstood, I thought you had the timing gear off. Since you didn't, there's no way the valve timing could be off. It doesn't matter if things move around with the valve cover off, the cam is locked in place with the timing gear and the cam followers just sit on top of the cam.

    With auto-decomp, it's not only the cable that could lift the exhaust valves but the extra inertial lobe on the camshaft. I don't have auto-decomp so maybe someone else can comment, but it's possible your valves seemed too tight because the decomp lobe on the cam was opening them slightly at TDCC. I think you can hear a little "clack" when the auto-decomp lobe comes down after TDCC. Maybe try adjusting the exhaust valves again and wait for the "clack" -- if your exhaust valves look way too loose this time, that's your problem.
  14. mik-ktm400rxc

    mik-ktm400rxc 4-stroke nOOb

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    I'm lost. I have adjusted the valves every way imaginable, too loose to too tight, and every way in between. I made sure the decomp wasn't putting pressure on the valves per katumo's suggestion. Alas, it never even sputters... Just turns and turns...
    I moved some wires around to more convenient and hidden locations when putting her back together. I thought that could be the source of the problem. But she still has spark...
    I didn't mess with the carb... And when I give it starting fluid she runs for a second or two then dies.
    I can't think of where to start or what to check from here?!
    Any suggestions from anyone on what to check? I messed with so much- wires, valves, water-pump- I have no idea where to start.
  15. katumo_jtb

    katumo_jtb bogus journeyer

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    The fact that it runs on starting fluid suggests that you have compression and spark, but no fuel. How long has the bike been sitting? If it's been a couple months since it ran, the pilot jet could be clogged with dried up gas. That's happened a couple of times to me.

    I've been able to blow out the carb with lots of choke and throttle while starting. If you start to smell gas, it's flooded and you'll need to try again later. Or you could pull the float bowl and spray carb cleaner through the jets.
  16. mik-ktm400rxc

    mik-ktm400rxc 4-stroke nOOb

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    So it was a bad stator! How in the hell it went bad when I was changing my water pump is beyond me... Bad luck! I checked the spark after messing with my valves and timing for around 15 hours.. Ha! Spark was weak and not firing right, so I checked the Ohms on the stator... completely off! New stator and she fired right up!

    Thanks for the help Katumo.

    Although, now she pop, pop, pops on deceleration. I put in a larger pilot jet and checked the carb for leaks, but it still pops, though less.

    My question is; with a new stator with a strong spark as opposed to an old stator that maybe had a weak spark, would the gas be burning more efficiently/quicker now, creating a lean condition in the unchanged carb/engine system? or maybe my valves being too tight or loose from all my adjusting is causing the popping? I double checked them, i could slide a .13 in barely, with a lot of resistance, and a .1 slid in with slight resistance... the spec is .1, should i tighten them so I can't get a .13 in at all? I'm scared of burning up the valves so I figured a little loose is better than too tight :huh

    Any ideas, theories or even wild guesses would be much appershiated!
  17. tananita

    tananita Adventurer

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    Basque country.
    Mine :)

    Now I have improved with some retractil mirrors and enduro tyres.

    97 20 000 km

    [​IMG]
  18. wayno

    wayno Long timer

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    Lets keep this going just bought 98 629RXCe...first KTM since Penton in early 70's and lots of good info....

    Bump:1drink
  19. wayno

    wayno Long timer

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    First off finally got the oil changed and have some ideas on how to to make the job easier and quicker next time.

    New prob: Bike burped/puked fine and battery has been getting weaker as time goes on and not sure how old.
    Symptoms: Bike Starts and seems to idle fine...while idling it all of a sudden dies no sputter, nothing just dies.
    Im pretty sure needs battery but acting like could be stater and bike is running off battery till not enough juice.
    Battery needed most likely.
    Stator?????? Hope not
    What ya think?

    Sorry bout wordiness
  20. wayno

    wayno Long timer

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    first off battery as it cant hold a charge