Help with piston Crf250r 2008
  • crosswolf
    Posts: 3
    Joined: Tue Jul 04, 2017 4:26 pm

    Help with piston Crf250r 2008

    by crosswolf » Tue Jul 04, 2017 4:37 pm

    Hello guys! Plz help me with piston. Piston on my crf250r 2008 is dead. But I have piston and rings from crf250r 06-07 years. Can I install it on my honda or not? Will it connect? Sorry for bad english.
    What maybe wrong?
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    JimDirt
    Posts: 2617
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: Help with piston Crf250r 2008

    by JimDirt » Tue Jul 04, 2017 7:40 pm

    Welcome to the site !! \:D/

    When you say the "piston is dead" , can you elaborate please ?? , did it lose compression ?? , did a valve poke a hole in it ?? , did it seize up ?? , is it blowing oil out the exhaust ??


    According to what i see in the Honda Parts Fiche , they each have different part # , but it does not signify what changes were made , Ken (the owner) would know for sure , but my Factory Honda Service Manual covers from 04-09 CRF250R , , and the only difference i see mentioned is the Top Ring Marking differs , it goes 04-07 , then After 07 , same goes for Ring End Gap , it lists 04-05 then a different gap for After 05 , then Piston Ring to Groove Clearance is one size from 04-07 , then another size for After 07 , what significance that has as far as actual cross fitment , i can't say for sure , but it does list differences , the only thing i could say , is take a digital Micrometer and measure each and see if there is any physical differences , other than that , i would guess that as long as the rings match the piston i would think it would cross fit between those years you have , again to be 100% sure i would PM (Private Message) Ken the owner here

    https://www.crfsonly.com/forum/memberli ... rofile&u=3 go to where it says "PM:Send private message" and click on the words private message

    These are the Honda Part #: :::NOTE::: The Parts Fiche lists a Piston A and a Piston B for 2007 , so i don't know what significance that has either , so its saying for 07 there are 2 different pistons

    (2006) 13101-KRN-850 PISTON 61.99
    (2007) 13110-KSK-730 PISTON A 76.99
    (2007) 13120-KSK-730 PISTON B 76.99
    (2008) 13101-KRN-A10 PISTON 71.99
    02 CRF450R
    06 CRF450X
  • crosswolf
    Posts: 3
    Joined: Tue Jul 04, 2017 4:26 pm

    Re: Help with piston Crf250r 2008

    by crosswolf » Wed Jul 05, 2017 3:42 am

    I have crf250r with ~100 hours. What I mean "piston dead"? When I have training day, after 15 minutes I have much oil in airbox. Valve gaps = 0.10. I watch my piston and it was weary. Std piston by honda. I have new std piston #13101-KRN-850 and rings # 13011-KRN-850. Can it connect to my honda 2008? I read honda 2006 have 12.9:1 compression and 2008 have 13.1:1. Pistons look the same.
  • User avatar
    JimDirt
    Posts: 2617
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: Help with piston Crf250r 2008

    by JimDirt » Wed Jul 05, 2017 9:29 am

    To be honest , if i were you i would just buy the correct piston for the year bike you have , if in fact the 06 compression is lower than the 08 , you WILL notice a difference in less bottom end power delivery , , as far as oil in the airbox , are you noticing a decrease in oil in the engine itself ?? (are you having to ADD oil to the engine ??) , is it possible you are over oiling the filter ?? , and have you checked compression ??

    If its blowing/losing that much oil then you would also have minimal compression , the bike would be difficult to start , etc , , i am just verifying your symptoms , as 100 hours is not excessive , but you did not mention that you are getting oil out of the exhaust , so i would think the oil issue is not related because if the rings were bad , you would also see oil/smoke out the exhaust , and would be more noticeable than oil in the airbox

    With that said , i would suggest getting the correct piston for your year , the cost is minimal and you would be happier with the performance results of the 2008 piston , more than you would with the 2006 piston..
    02 CRF450R
    06 CRF450X
  • crosswolf
    Posts: 3
    Joined: Tue Jul 04, 2017 4:26 pm

    Re: Help with piston Crf250r 2008

    by crosswolf » Wed Jul 05, 2017 12:30 pm

    Sorry,I forgot to write about oil in exhaust. When I stop and open full gas, I see gray smoke from exhaust. In airbox it was motor oil. Bike worked bad.
  • User avatar
    JimDirt
    Posts: 2617
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: Help with piston Crf250r 2008

    by JimDirt » Wed Jul 05, 2017 3:07 pm

    OK , that makes more sense , but as mentioned , i would go with the correct piston for your year , i am not saying that the one you have will not work , what i am saying is the correct year will work "better" performance wise because of the higher compression , make sure the cross hatching is still looking good in the cylinder itself ,you should be able to see the cross hatch but not have any ridge at the top of the cylinder and to make sure the cylinder is not glazed over , which could allow even the new rings to not be able to seat correctly , if you have access to or know someone with a internal micrometer , check the bore for roundness and to make sure it is within spec , if its out of spec then i would not waste time installing a new piston until the cylinder is replaced , if its within spec , then you should be fine

    If you need the tolerance specs i can list them if you don't have access to them
    02 CRF450R
    06 CRF450X

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