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Help Missing 10 hp at 2KR

Discussion in 'Yamaha 250cc In-Line 4's' started by cornulio81, May 5, 2020.

  1. cornulio81

    cornulio81 Active Member

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    By the way, does anyone have experience with the China Piston with Ring Sets? Zlthe are China typical unbelievable cheap, but is the quality also unbelievable bad?


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  2. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    I have had success with the AHL brand ones in my 3LN
     
  3. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Okay, so most likely new rings, deglaze the bore and give the head and valves a once over.
     
  4. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    Have used the Chinese rings and piston sets with good results. If your bores are good then I suggest get the pistons and the rings. Can also be purchased in oversizes too.
     
  5. cornulio81

    cornulio81 Active Member

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    OK, thanks. So China Pistons could be worth. Are the OEM Pistons Aluminium oder Steel Pistons?
    I am asking, cause the Chinese once are advertised as steel

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  6. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Pistons are alloy, top compression ring is usually chrome and 2nd ring is steel. Make sure your order the right rings/pistons as 2KR and 3LN are different.

    The cylinder sleeves are cast iron. There are also o-rings at the bottom to seal the water jacket from the rest of the crank case, it's worth replacing them if you are going to have the head and cylinders off. I also suggest avoiding the chinese head/base gaskets and use genuine ones instead.
     
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  7. cornulio81

    cornulio81 Active Member

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    Yes, I usually change all sealings which are disassembled. All other would be....hehe.
    I only have doubts to use steel instead of Alu pistons, due to the heigher weight and the Forces at higher piston speeds....
     
  8. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Steel piston's ?
     
  9. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Pistons are alloy, second "ring" is steel - remember English is not his mother tongue, and all told he's doing wonderfully at communicating difficult concepts with specific terminology in another language

    And just re-reading that, likely you've encountered a poorly translated aliexpress page, which says that the pistons are steel - in fact they are Aluminium Alloy

    Use the AHL seller pages on aliexpress as their quality seems to be the best
     
    Last edited: May 6, 2020
  10. cornulio81

    cornulio81 Active Member

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  11. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    I would get those piston kits if your bores are ok. (It really does say stahl (steel) in the advert).
     
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  12. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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  13. cornulio81

    cornulio81 Active Member

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    Super, Thanks! Is this for 1 or 4 pistons? It's a confusing describtion.
    The ebay set Is looking like alloy, even if it's called steel, but never know....
     
  14. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    It would be for a set of 4
     
  15. cornulio81

    cornulio81 Active Member

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    Thanks for you Infos so far.
    Is this the compression part from the service manual? makes sense... I searched 3 times:minigun:
    Would mean 10 bar max., 8 bar min. and max deviation 1bar between the cylinders?
    upload_2020-5-6_10-35-47.png
     
  16. cornulio81

    cornulio81 Active Member

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    So, I will do now the standart procedure:

    -Compression test with warm engine.
    -Compression test with fill some oil into chamber.
    -->If compression with oil still bad, valve checking.
    -->If compression with oil better, I can start disassembling
     
  17. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Valve clearances anyway, they may require adjustment at any rate
     
  18. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    Don't forget to hold the slides of the carbs open, not just the throttle.
     
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  19. cornulio81

    cornulio81 Active Member

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    Hello everybody,

    I only wanted to state, that i didn't came Up to now to check fürther.
    Hopefully this Week *eek* :)
    Maybe i forgot to say that i have the Bike since 21 years now (but 10 years with a garage Carrer) *eek eek*

    I am pretty sure, you guys should have German Beer in your wishlist for next Christmas *eek eek eek*

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  20. cornulio81

    cornulio81 Active Member

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