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Thread: Top end damaged, need help!

  1. 10-16-2006, 09:53 PM #1
    MathGSR98
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    Top end damaged, need help!

    Hi folks,
    I just got my 85/86 atc 250r disassembled for inspection... (When you have the feeling that it's time to invest before everything breaks...). I removed my cylinder and I had a bad surprise: A big scratch from the top to almost the bottom. My crank also seems to have some damage.

    My piston is a wiseco 526p2 0.50mm over. I'm wondering how much oversizes left I have (86 cylinder)? Here is a pic or my piston, what is the cause for all the small holes on it?


    The cylinder... we can see the large scratch in the middle. I don't know what got blasted in it... Is it possible that it will need to be bored 2 sizes over the get rid of it?



    Here is my crank. It is just in that position that I can see it's damaged. My bike was running fine though. The rod has no play up and down and a slight play left/right, is it normal?




    My head seems ok excepted for the carbon... What is the cause for such accumulation?



    The previous owner had grinded the inside of the intake as you can see. Is it a good idea, should I grind it more?



    Thank you so much for any help and sorry for my bad english.
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  2. 10-16-2006, 10:02 PM #2
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    SYKO
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    play on the rod left to right some is ok, but up in down its doen for! somehow it looks liek soemthing broke somewhere causing all the piston damage, rings still good?
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  3. 10-16-2006, 10:04 PM #3
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    Somekindofjerk
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    Looks like your preivous owner had a bearing spin in the bottom end or maybe a piston come appart. Did you put that piston in? Carbon is usually running rich or cheap two stroke oil.
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  4. 10-16-2006, 10:12 PM #4
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    well i'm no 250r expert but i think you could get away with only one bore over... you don't want to go too far.. incase something breaks again, you have room for another bore... i'd try to bore it out one (ofcourse after you get everything else straightened up) and see what it looks like... good luck with it...
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  5. 10-16-2006, 10:16 PM #5
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    Is that rod and piston pin blued? It looks like that R got really really really hot
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  6. 10-16-2006, 10:21 PM #6
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    Post a pick of the spark plug . Is it melted ? What about the needle bearing ?
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  7. 10-16-2006, 10:29 PM #7
    MathGSR98
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    Quote Originally Posted by sykolincoln
    play on the rod left to right some is ok, but up in down its doen for! somehow it looks liek soemthing broke somewhere causing all the piston damage, rings still good?
    The rings seemed to be good enough. Before I disassembled the trike, it was running well so I didn't blew it up.
    I made a compression test and I got 160-163lbs but my tester is kinda cheap...
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  8. 10-16-2006, 10:34 PM #8
    MathGSR98
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    Quote Originally Posted by Somekindofjerk
    Looks like your preivous owner had a bearing spin in the bottom end or maybe a piston come appart. Did you put that piston in? Carbon is usually running rich or cheap two stroke oil.
    No it's the previous owner who put the piston in and it's my cousin who made the job. I trust him, he rebuilt my old 97 cr250r and 86 trx250r...

    I guess the crank damage is caused by the previous piston come appart like you said or the bearing spin. So I guess I can go ahead without a new crank...
    Thanks
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  9. 10-16-2006, 10:38 PM #9
    MathGSR98
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    Quote Originally Posted by Somekindofjerk
    Is that rod and piston pin blued? It looks like that R got really really really hot
    I'm not sure about the rod and piston being blued but I can say that it has ran hot. I rode it the last winter (I'm in Quebec, Canada) without jetting it richer... I could feel like 25% more power but It was certainly running lean as hell... My fault... I don't have my piston/rod and pin in hand, so I can't say much.
    Thanks
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  10. 10-16-2006, 10:41 PM #10
    MathGSR98
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    Quote Originally Posted by Erics350x
    Post a pick of the spark plug . Is it melted ? What about the needle bearing ?
    I don't have my sparkplug to take a pic but it is not melted, it is just black with some carbon deposit on it. The needle bearing is fine. I can't detect almost any radial play if I try to move the pin.
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  11. 10-16-2006, 10:44 PM #11
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    maybe it sucked in some sand or mud?
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  12. 10-16-2006, 10:55 PM #12
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    Both the Circlips in the piston still? if so the dammage was Probably from running it so Hot,,,,,Aluminum melts at 1400 And it aint hard to get the motor that Hot when its running lean........or the bottem end wasnt flushed out properly when it was last rebuilt. could also be from not Cleaning the cylinder Properly From the last bore job/rebuild
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  13. 10-16-2006, 11:43 PM #13
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    The "DINGS" in the piston are from detonation...Either too hot or too lean..Not bad enough for Replacement IMO....Wiseco pistons are common for "Scratching cylinder walls....Cant tell how deep that is from the pic, but if it isnt too deep, It may be normal. ANyone else , verify this for me?
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  14. 10-17-2006, 12:55 AM #14
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    Wiesco pistons tend to need a little more clearance than a normal piston. Being more heavilly constructed they expand further than the specs in the book say. I have been told to add and extra thousands of an inch to the clearance to keep the scraping from happening. Allso, that piston retainer pin looks horribly blued, i would try to get a new one, or use an old one thats in decent shape. I had one but cant seem to find it....

    ***edit*** a nice new reed cage might be nice too, bring back some life
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  15. 10-17-2006, 11:53 PM #15
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    hone the cylinder ,and check the clearances
    clean the head and piston with a soft wire wheel / dremal tool / or sand paper ,and polish it see if they are still in it.
    they are so minimal i dont think it will matter,
    it ran ok? - it looks like mabe ya didnt warm it up,rings are good? , if it would have been a pin or something like that from the crank it would be bad, my suzuki was
    so was the head
    did the reeds break and get burnt in the cylinder???

    wisco pistons are great pistons follow the instructions -- relieve the exhaust bridge and what ever else they say to do
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