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Thread: 250r piston help

  1. #21
    Member Justin335's Avatar
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    I couldn’t find anything on led website for a 68 mm all I could find was things for a bigger bore any one got any suggestions I’m still not sure which piston I need either and not wanting to order the wrong parts

  2. #22
    Senior Member Action69's Avatar
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    Give LED a call he’s is real informative and will take the time to explain things to you.Regardless if you’ve ever done business with him or not..
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  3. #23
    Senior Member atvmxr's Avatar
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    Quote Originally Posted by Justin335 View Post
    I couldn’t find anything on led website for a 68 mm all I could find was things for a bigger bore any one got any suggestions I’m still not sure which piston I need either and not wanting to order the wrong parts
    before you go and order something, you need to determine your cylinder clearance. Just putting another 68mm piston in there may be a short term fix if there is too much cylinder clearance. The piston skirt will break and potentially trash your whole motor. The next size larger piston is a 68.50, 526MO6850 for wiseco. plenty of them for sale on ebay. However, once you go past the 2mm overbore (68mm) the standard headgasket will not work and ideally you would need to get your head rechambered to account for the increased surface area now part of the chamber on a 2.5mm overbore.

    no quick fixes if you want it done right.

    also you have a long rod per the HA2, so use the spacer plate with the 85/86 250r piston
    american opel likes this.
    88 x 2, 89, and LSR TRX250R's, 2x 88 blasters, 2x 85 350x's, 87/85 TRX350XR hybrid, 88 zilla, 92/87 Hybrid LT250/500R, 92CR250, 2014 DRR70, 2010 APEX RM85 Shifter Hybrid

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  5. #24
    Member Justin335's Avatar
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    How do u check the cylinder clearance

  6. #25
    Senior Member atvmxr's Avatar
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    Quote Originally Posted by Justin335 View Post
    How do u check the cylinder clearance
    you dont. take cylinder and old piston to a quality machine shop to have them measure. Like a place that would build a performance auto racing engine, if you dont have a good local dirtbike repair shop. You want clearance in the 0.0035-45 range. maybe a little bit more figuring some might be worn off piston as well as the cylinder.
    american opel likes this.
    88 x 2, 89, and LSR TRX250R's, 2x 88 blasters, 2x 85 350x's, 87/85 TRX350XR hybrid, 88 zilla, 92/87 Hybrid LT250/500R, 92CR250, 2014 DRR70, 2010 APEX RM85 Shifter Hybrid

  7. #26
    Member Justin335's Avatar
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    K we don’t really have any shops around here that build race engines we have a Honda dealer I will go in there tommorrow and c I’d tgey can check it out for me does anyone have a head gasket recommendation for the 68 mm or would stock b fine

  8. #27
    Senior Member american opel's Avatar
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    as other said you cant just order a piston and hope it works.it need the bore checked then usually a larger piston needs ordered then they bore and finish hone for new piston.if you dont have a shop around you send it to a shop.as for headgaskets oem is pushing it with a 68mm bore.and anything bigger the head gasket also needs bored...bdt motorsports can do all the work and also has the needed headgasket in stock.

  9. #28
    Member Justin335's Avatar
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    K thanks for all the help I will get it checked out and c wat all is needed to get it back together does anyone know what might of caused the piston to melt

  10. #29
    Senior Member matuus's Avatar
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    do it right n send 2 bdt motors carlos. bdt can measure n bore. cut head. cut gasket. they have everything in stock.


    Sent from my iPhone using Tapatalk

  11. #30
    Senior Member aztecgwynn's Avatar
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    This is how I ID OEM stock crankshafts
    KA4 1985 Honda ATC 250R Short Rod
    HA2 1986 Honda ATC TRX 250R Short Rod
    HB9 1988-1989 Honda TRX 250R Long Rod
    Now 1987 I really don't know much about that year was already morphing into an 88 so it has many differences from an 86 and allot of similarities from an 88
    Good luck


 
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