Vintage KTM GS500 dirtbike any info?

Discussion in 'Thumpers' started by herman maire, Jul 25, 2012.

  1. herman maire

    herman maire Been here awhile

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    I tried posting this in the " Old's Cool" tread but no replies.

    Does anybody know any details on this model bike? I came across this early 80's 4stroke KTM GS500, it needs to be restored as the timing belt broke so engine needs a rebuild . They are asking $600 but I was thinking of offering $400 but I cant find any engine part parts available. Does anybody know a parts source for engine parts?

    Any thoughts? Its very possible its just not worth the headache. How would this compare to a CR500 honda ?

    Any replies appreciated.


    [​IMG]
    #1
  2. Navin

    Navin Long timer

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    Rotax powered, see Ron Wood for the lump parts.

    It is a friggin tank. You can build it for big power but it will always be heavy and enormous. This bike made the LC-4s of the 1990s seem small and light!

    Cool bike still, you don't see many/any anymore. Rare even back then.
    #2
  3. nevgriff64

    nevgriff64 Super Moderator Super Moderator

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    Lets move this over to Thumpers and see what they can add. :thumb

    Orange Crush is for KTMs, but designed for 950/990 twins.
    #3
  4. what car??

    what car?? down the road

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    Buy it! If anything else you have a cool bit of history. I would buy it if I came across a cool bike like that one. Just my two pennies...
    #4
  5. BIG ED XT FAN

    BIG ED XT FAN Long timer

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    I rode a enduro in florida and there was a guy on that bike. Did wheelies all day long!!!! Great power!!1 The front forks are from a yamaha yz model i think?? I think the forks were white power models. :eek1:lol3 I buy it, you just do not see bikes like thay anymore!! Think it as art.:deal BiG ED XT&TT 600 FAN!!
    #5
  6. MZRider

    MZRider Neo-Luddite

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    Another one has surfaced!
    Check out this discussion on ThumperTalk:
    http://www.thumpertalk.com/topic/970930-1983-ktm-rotax-need-info/

    Here's the information I posted in case you can't access it there:

    You're in luck - I searched the internet for a manual - any manual for years, and eventully managed to buy one. I can make a copy of my KTM factory original Owner's Repair Manual for you. May take me a week or so as my copier is broken and I'll need to go to the local Staples. If you need it quicker, I may be able to scan a few pertinent pages and send them to you. I will need your email address to do that of course, please email me at c.d.mullendore@att.net.

    Here an interesting article about the KTM 504:
    http://www.cifumotor...3ktm/index.html

    The Rotax engine in the KTM 504 is pretty well supported as it was used in lots of different bikes. For starters, I'd check with Keith at American
    Dirt Bike: http://www.americandirtbike.com/ and Ron Woods Racing: http://www.rotax.net/ .

    If your bike has the original Bing carburetor on it, parts are available here:
    http://www.bingcarburetor.com/ .

    Chassis parts are a bit harder to source, Andre Horvath's KTM Klassiker:
    http://tinyurl.com/86yrtxq is probably your best bet there. Some parts are off the shelf items (example: the front brake system shares parts with numerous small Italian bikes of the era). I do have most of a rolling chassis stashed in my attic from when I was attempting to build one from parts.

    If you want a CD copy of the manual, I'll burn one for you.

    Front forks are made by Marzocchi, rear shocks is a Fox Twin Clicker, front brakes are Brembo. DC Plastics sells some replacement bodywork.

    I'd grab that in a heartbeat for $600. If you decide not to buy it, let us know. Someone here would like to I'm sure!
    #6
  7. mmurry

    mmurry Adventurer

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    rotax motor parts are still available but VERY expensive... and it is usually best to have a guy familiar with them do the work....
    #7
  8. rz35027

    rz35027 Been here awhile

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    Real cool old bike! And it looks to be in really good shape (except for the motor?)

    Think of an old XR500 Honda, only alot better. It's a fast tank = does not compare to a CR500...
    #8
  9. WIBO

    WIBO Will it buff out?

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    #9
  10. herman maire

    herman maire Been here awhile

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    Thanks for all the replys, you all pretty much gave me the motivation to go and buy it. I decided to just take a gamble on it even though Ron Woods suggested I only buy it if I take the cylinder head off and inspect for damage. The owner was not very negotiable on the price surprisingly.

    I went to pick it up at 9pm, got the bike back home and in the garage by 10pm and was already dismantling the bike.
    What I started with [​IMG]

    A few hours later [​IMG]

    For some reason it was like I was a possessed maniac :happay , I could not stop wrenching until it fully dismantled :D
    [​IMG]
    #10
  11. herman maire

    herman maire Been here awhile

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    I did receive 2 new timing belts with the bike purchase, they were purchased at a Harley Davidson dealer for a bike that used the same Rotax engine . Its the original DAYCO brand . [​IMG]


    Once I got the engine out, I could not help but have a look inside the valve covers, everything looked really good, to me anyway [​IMG]
    #11
  12. WIBO

    WIBO Will it buff out?

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    Congratulations on your purchase....

    You've bought a piece of rare moto history....

    Keep the pics coming or start a new thread?

    Good luck with the moto

    :D
    #12
  13. MZRider

    MZRider Neo-Luddite

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    My offer of a free manual on CD stands.
    #13
  14. Kawidad

    Kawidad Long timer

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    :lurk
    #14
  15. Kai Ju

    Kai Ju Long timer

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    The right side, as viewed, valve cover bolt hole appears to be cracked and stripped, maybe get it welded and recut the threads.
    Also, if the valves are bent you should have a very large amount of clearance at TDC compression. If they are in spec, or at least close, you should be ok. Do a leak down test to verify.
    I had one of these engines in a 250 Ninja and used to ride the crap out of it for about 20,000 street miles.

    Have fun with that one.
    #15
  16. dokerty

    dokerty n00b

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    I have the same bike, stumbled across it a while back. been in the shed for some time, took a while to get required parts together. seat tank etc.
    I have started to take it apart lately. got engine parts from Peter Knight in the uk. www.rotax.co.uk gaskets, etc.

    Looking for some one to rechrome the forks for me at the moment.

    What are the plans for your bike? full restoration?
    I am still not sure of my bikes history, wheter it was an original gs dual sport or off road only, so not sure of direction yet.

    I need to get my hands on head bearings and fork seals, any ideas?
    #16
  17. herman maire

    herman maire Been here awhile

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    Dokerty,

    Cool, is your bike the same year as mine ( 1982 ) ? What was the condition of your engine like? Other than a new piston and a bore, my engine appears to be in perfect condition.

    Is there damage/wear on your front forks pistons? I honestly dont know if you can rechrome them, I am sure other members on this forum would know. I would be curious to know also, luckily the chrome on my front fork pistons are in great condition. I am going to have the lower front fork body's anodized .

    Another member posted link earlier in my tread that appears to have quite a extensive amount of vintage KTM parts, have a look
    http://enduroklassiker.com/artikel/

    I am doing a full restoration on my bike but not to the point where you dont want to use it, I am starting to really, really like this vintage Austrian bike. I honestly dont know if my bike was originally a dual sport or off road model but I am going to restore it to be a Dual sport, its just much more fun to be able to drive to the trails VS having to put the bike on a trailer.

    Post some pics of your bike when you get a chance. :clap
    #17
  18. herman maire

    herman maire Been here awhile

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    Wibo,

    Thank you for the kind words. I would have though that these bikes were more common in France than Canada.


    YES, YES I am interested. Would this CD work on a Mac? I would really appreciate this.
    #18
  19. herman maire

    herman maire Been here awhile

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    Heres a few more pics of the engine tear down, this is as far as I will be going as the bike only had 4500 miles and everything appears to be in very good condition internally.

    Once I removed the head, there was zero contact with any valves.

    Bk brkr baker, it looks like you are correct, this appears to be a non-interference head or just got lucky
    [​IMG]
    [​IMG]

    The only problem that I found was with the piston that had a broken ring seat, what surprised me the most was that this was an original hight quality MAHLE piston. I would not expect a MAHLE piston to have a problem like this. There was no other damage to the cylinder.
    [​IMG]

    I have all the new original Rotax engine parts ordered from Elliot at Ron Woods racing , they were great to deal with and took the time to answer all my annoying email question. A new oversized Forged MAHLE piston has been ordered.
    #19
  20. tdrrally

    tdrrally Long timer

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    #20