Super Sherpa thread

Discussion in 'Thumpers' started by AZstrommer, Sep 3, 2007.

  1. 250senuf

    250senuf Long timer

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  2. CharlesH

    CharlesH Support those who support you.

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    What psi have people running shinko 244's been using?
  3. swiftrabbit

    swiftrabbit n00b

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    Great thread BTW. I've had my Sherpa for a few years, and have just recently tore into it for maintenance, valve check, and jets.

    Anyone have luck sourcing a valve gasket online? I've looked and can't find any that match what I have. I'd use gasket sealant but the large gaps near the cam sprockets would be a problem.

    Thanks in advance!

    2001 Super Sherpa
  4. bajasam

    bajasam Been here awhile

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    partzilla
  5. swiftrabbit

    swiftrabbit n00b

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    Excellent source. One left in stock too!

    Thanks!
  6. OrganicGrant

    OrganicGrant n00b

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    Have TWO stock super sherpa steel tanks and a nice tear-free factory seat for sale. One tank is dent free, other has a ding.
    $100 and $80 ea, seat $60 plus actual shipping from 28806.
  7. mike21b

    mike21b Been here awhile

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    Paved roads, 28-30 psi. Gravel or off road, 22-24 or even lower (say, 20 minimum unless you have rim locks on it).

    I usually have mine at 25 psi unless I know that it will be all pavement.
    CharlesH likes this.
  8. mike21b

    mike21b Been here awhile

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    Someone fairly recently was desperately searching for a Sherpa seat or even a seat pan - they are rarely available anywhere. Problem is, I'm on three different lists that discuss Super Sherpas and I don't remember who and when.

    What year are the tanks from? Do you have pictures? I'd be willing to buy all three items - not because I need them, but so I could help out a fellow Super Sherpa owner at some future point by selling them to that person for the same price you're offering them for.
  9. Aseniya

    Aseniya Adventurer

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    I'm looking to buy side racks for my 2002 Super Sherpa. Any one selling?
  10. mnfrank

    mnfrank Adventurer

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    Sherpa spotted!! Minneapolis CL -- 1999, gold wheels, low miles, $2k looks new
  11. NJ-Brett

    NJ-Brett Brett

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    Here is how, and its very common on many/any brand bike where the valves are ignored:

    Someone does not check the valves and the exhaust gets tight. Exhaust seat wear is higher then intake seat wear or cam wear.
    The exhaust valve head gets rid of the heat by seating firmly against the seat in the head.
    If the valve does not seat well it gets VERY hot and melts and/or bends or the head breaks off, but mostly they stick open
    and get hit by the piston.
    They can weld to the valve guide in any position though.
    So the valve stem will not move yet the cam lobe (or rocker) is trying to push it open, something has to give...

    It never seems to happen with the intake valve as its cooled every opening, its always the exhaust valve.

    The valve can be partly stuck open when the piston hits it and bends it up.

    Excess play in the valves only makes things have a lot of noise.
    Not enough play will ruin your day.



  12. tlrmark

    tlrmark n00b

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    Its pretty obvious in this case the failure had nothing to do with valve clearance.
    The camshaft seized in the cam journals from a lack of lubrication.
  13. bajasam

    bajasam Been here awhile

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    Well Brett, somehow these newbs are stuck on this cam seizure thing even though both cam sprockets and chain are in fine condition, they just cant seem to understand the forces that caused that cam bearing cap to fracture. you can lead a horse to water..............................
  14. Windborne11

    Windborne11 Been here awhile

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    Heh..Heh. So what caused the cam journal to seize?
    Heh.. Heh.. So how does the engine start and run with an exhaust valve slightly open?? or even tight?
  15. NJ-Brett

    NJ-Brett Brett

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    I have no idea why this failure happened, but its common to burn a valve and have the same kind of results.

    Here is how it works, the valve play is tight but the valve closes when cold.
    The valve gets hot and expands and does not close all the way, the motor still runs fine, maybe down on power a bit.
    The valve gets even hotter and longer and the head breaks off or it welds itself in the guide.
    This is WHY they make you check the valves on engines without hydrolic lifters and why they have a minimum play that is ALWAYS wider on
    the exhaust valve.
    The exhaust valve MUST close all the way and for long enough to get rid of the heat or it melts.

    If the cam seized, I would think the chain would break and then other bad things would happen.
  16. Windborne11

    Windborne11 Been here awhile

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    Other bad things did happen. What happened here was there was a lack of lubrication, which ALWAYS shows up at the cam journal first, as it is the part of the engine that is farthest from the oil pump, which is in the bottom of the motor. The cam seized, at high RPM, at the time when the exhaust valves were open, but the inertia of the crankshaft caused the lower cam sprocket to jump some teeth on the camchain, which allowed the piston to slam into the open exhaust valves. The exhaust valves were driven upwards into the cam by the piston, forcing the left journal cap to snap. The right journal cap was supported by the VERY tight camchain, which is why it did not snap too.
    oakcutter likes this.
  17. bajasam

    bajasam Been here awhile

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    What a crock,you cant starve the exh valves without starving the intakes also, but they have no signs whatsoever of any damage.Heh-Heh-Heh. And he also stated it started losing power slowly and steadily before the bearing cap fractured, no mention of a sudden failure Heh-Heh-Heh
  18. Windborne11

    Windborne11 Been here awhile

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    I guess you have never had a motor apart, which is OK. The valves themselves are not lubricated by the oil pump, and most final seizures are lead by a minor
    seizure which slows the engine down prior to it locking up. There is one particular point on the cam where all 4 valves are open the same amount at the same time, but there are many points where only the exhaust valves are open. In this case the final seizure occurred when only the exhaust valves were open.
  19. NJ-Brett

    NJ-Brett Brett

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    Sorry, but the valves are lubricated by the oil pump.
    They don't get a lot of oil, but they do get some.

    My guess (and it is a guess) is the exhaust valve got hot and did not close all the way which put steady force on the cam causing the scoring, then the valve stuck open and things broke.
    If it was lack of oil, both cams would be toast.
    With a lack of oil, I think something else would go first, but most of the lower parts might be splash lubed if there was oil in the motor.
    On bikes that lost all their oil, its usually the piston or wrist pin area that fails first.
    The cams will rattle around a lot with whatever oil film is there, for quite some time.

    Well, we may never know, but its a very good idea to check the valve play when its supposed to be done, otherwise the result
    is the same as here, even if some don't want to believe it....and I have had a lot of motors apart...
  20. bajasam

    bajasam Been here awhile

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    A "minor seizure"...............................Lol