help me figure this one out!

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by rockohlic, Sep 29, 2013.

  1. Sumi

    Sumi Long timer

    Joined:
    Mar 30, 2010
    Oddometer:
    1,897
    Location:
    Hungary
    IMO at TDC the marks (circle at the base of the teeth on the cams (see picture below) at the front cyls) on the cams should line up with the heads surface, so if you rotate the engine to TDC, and the marks on the cams are lined up there correctly, then it didn't skip a tooth. The front cam lobes should be pointing away from each other at TDC.

    If they don't line up at TDC, I think you can just pull the bridge (!!!make sure the valve springs are not puting a load on it (there should be a gap between the buckets and the lobes - this is btw the gap that you adjust at a valve adjustment)!!!*, or it will crack - and because they're paired with the head, it's an expensive lesson), and reset the cams.. Instead of my first post in the thread I think there is no need for a degree wheel to perform this.

    * Hope you haven't made any damage to it when you did the leakdown test - as you wrote in post #13 that you have loosened the bridge and turned over the engine that way.. BTW if the leakdown test says that it won't hold any PSI, then apart from the cams position to the crank, there is something else wrong in there:(

    there are some good thoughts on this link:

    http://www.ktm950.info/how/Orange Garage/Valves/cpmodem_method/valve_adjust.html

    [​IMG]
    #21
  2. pdxmotorhead

    pdxmotorhead Long timer

    Joined:
    Mar 4, 2012
    Oddometer:
    1,144
    Location:
    Portland OR
    The chamber on these is tiny,, you can hydro lock a cylinder with a very tiny amount of fuel. I found a reference at one point that its less than 10CC to do things in..

    Good Luck!

    PS: Use the Rotax valves they are top notch..

    Dave
    #22
  3. Zuber

    Zuber Zoob

    Joined:
    Sep 28, 2004
    Oddometer:
    2,631
    Location:
    Main Street, Shedd, Oregon
    Ahhh, the pages of inquiry slowly reveal.... You may have a burned valve, not just due to this tip over, but from them being run with no clearance. You may have been the first person to check the valve clearance.

    Keep us in the loop when you pull it down. Check the cam timing on the way in.
    #23
  4. rockohlic

    rockohlic Been here awhile

    Joined:
    Oct 22, 2009
    Oddometer:
    137
    Location:
    arizona
    does anybody know the trick to remove the cam chain from the top cam gear so that the head can be removed. Does not seem to b e enough room between the gear and the side of the casting on the cylinder head.
    #24
  5. rockohlic

    rockohlic Been here awhile

    Joined:
    Oct 22, 2009
    Oddometer:
    137
    Location:
    arizona
    never mind, you feed the cam chain of towards the center of the engine. And the gear comes strait up! ef me with a shoe
    #25
  6. Sumi

    Sumi Long timer

    Joined:
    Mar 30, 2010
    Oddometer:
    1,897
    Location:
    Hungary
    haha:)

    Don't forget to post pictures!:)
    #26
  7. rockohlic

    rockohlic Been here awhile

    Joined:
    Oct 22, 2009
    Oddometer:
    137
    Location:
    arizona
    Took head to cycle machine shop(very reputable) and the intake valves are wore out. 21,000 miles and the valves are so far into the seats there is not a lot of sealing surface left. Anybody from H.O.W. reading this, have you ever heard of such a thing?
    #27
  8. Zuber

    Zuber Zoob

    Joined:
    Sep 28, 2004
    Oddometer:
    2,631
    Location:
    Main Street, Shedd, Oregon
    I've seen that on lots of motors, when the proper clearance wasn't kept. Normal result for tight valves.

    May you serve, at least, as a bad example for others. (sorry)
    #28
  9. rockohlic

    rockohlic Been here awhile

    Joined:
    Oct 22, 2009
    Oddometer:
    137
    Location:
    arizona
    actually I bought the bike used and put in the truck, brought it home and immediately tore it down for a valve adjust. BTW you don't need to turn the motor over for a leak down test, so it is safe to loosen the cam towers.(provided it is at tdc) Unfortunately the lesson to learn here is: when you buy a used bike, (even though from an inmate) it may not have gotten proper maintenance.
    I appreciate the feed back from you guys, it was very helpful. The worst part of a diagnose and fix is not riding the bike especially during perfect weather!
    #29
  10. pdxmotorhead

    pdxmotorhead Long timer

    Joined:
    Mar 4, 2012
    Oddometer:
    1,144
    Location:
    Portland OR
    How do you do a leak down without having all the valves closed and to do that on both cylinders, you'd have to turn the motor? You got me curious.. :)

    BTW I use air through the sparkplug hole and a leakdown guage..

    Dave
    #30
  11. rockohlic

    rockohlic Been here awhile

    Joined:
    Oct 22, 2009
    Oddometer:
    137
    Location:
    arizona
    one cylinder at TDC at a time. add psi to leak down tester, calibrate to zero then connect to hose/fitting that is in cylinder. Read the gauge showing % of loss, do not focus on the psi number. There may be other testers that work differently, however mine works likes this. I loosened the cam towers just in case my valves were so tight that the cam(part w/o lobe) was putting pressure on the buckets thus keeping them slightly open giving me a false reading.
    #31
  12. pdxmotorhead

    pdxmotorhead Long timer

    Joined:
    Mar 4, 2012
    Oddometer:
    1,144
    Location:
    Portland OR
    OK,, same as mine,, your just only turning it to get to TDC not spinning like compression test.. :) Cool..

    I always use 100 PSI on leakdown, makes the % easier to do in my head.. LOL

    Dave
    #32