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  1. #1

    Default Scratched CR500 Cylinder, updated with pics of piston

    Alright, I was out on a local MX track a few weeks ago, after a few laps we took a break, when I went to start the bike for a few more laps I noticed a whisteling sound, and sure enough, my bottom cylinder gasket had blown.

    I finaly get the gaskets and open the engine only to find this


    the scratches are not deep but I can feel them with my finger, I guess a hone and a new piston will get me going again, but I want all of you guys opinions on what happend here.
    to me it looks like overheating, could it be I've been running with a leaking gasket a long time, causing a lean condition? could it be I was running lean during this winters iceriding?

    the rest of the cylinder looks good to me.

    Last edited by 2strokeviolence; 06-05-2010 at 05:21 PM.
    whenever I fire up a 2-stroker, the primitive caveman inside me wakes up and goes on a rampage!!
    My Stable O'Bikes
    -94 CR500R - BigBoreBrute...
    -00 XR650R - The Big Red Pig.
    Suzuki TS 50 - Broke piece of crap
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  2. #2

    Default

    im pretty sure its just from runnin lean same thing happened when i hot siezed my cosins bike. i heard a whistle then the rear tire locked pulled the clutch stoped let it sit for a min kicked fired it up rode home told himto put 1 size bigger jet on it, well he didnt cuz he was like its jetted perfect a week later he blew it up. and a professional company rebuilt that lol
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  3. #3
    Join Date
    May 2007
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    Default

    That plug looks pretty good. Could've been lean last winter, did the damage then, and the plug has since regained color now that the warming temps have richened it back up. But it is possible that you did this at the track and the plug just hasn't burned off the color yet.

  4. #4

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    if this happend during winter then I've ridden over 7 hours of effective riding with the cylinder like this, wouldn't it seized completly after a while? this looks like a pretty fresh damage to me. the bike started one kick and had good compression (my right foot says so atleast) it ran strong also. piston has a total of 29hrs on it.

    more opinions is welcome, I'm hoping a light hone and a fresh piston is the way to go here.
    whenever I fire up a 2-stroker, the primitive caveman inside me wakes up and goes on a rampage!!
    My Stable O'Bikes
    -94 CR500R - BigBoreBrute...
    -00 XR650R - The Big Red Pig.
    Suzuki TS 50 - Broke piece of crap
    -93 Honda PX-R 50

    Take a look at my bikes : http://s294.photobucket.com/albums/m...tzen/?start=64
    My Youtube Channel : http://www.youtube.com/user/lauritzen2

  5. #5
    Join Date
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    running a touch lean, or the exhaust bridge wasnt relieved correctly.
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  6. #6
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    Almost looks like it was eating some dirt some how.

    Can't see him but there is a guy on a banshee under all that roost.

  7. #7
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    May 2005
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    that looks like aluminum from the piston! i would say that its from the blown gasket causing a lean condition. I have seen your vids and if it wasnt jetted right it wouldnt have lasted that long! whats the piston look like?
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  8. #8
    Join Date
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    Quote Originally Posted by tecate 4 rider View Post
    Almost looks like it was eating some dirt some how.
    if it was eaing dirt, it would have torn up the intake side first. definitely looks like the machinist didnt relieve the exhaust bridge. because if it was lean, it would have scuffed the other side a little when the exhaust side of the piston expanded.

    either way, this didnt happen in the cold months, then just cause problems now. everything happened right at that instant.

    I know what a lean sieze looks like...did it twice to my 300R before i discovered a tiny air leak in the damn intake...... that resembles poor machining
    Toys:
    84 250R, 300 kit, Balanced Crank, FLOTEK porting, Wiseco piston,38mm Keihin, Vforce 3, DG type II, UNI Filter
    1980 XL80S
    6.5 HP minibike
    2002 Ranger,Junkyard rebuild
    1969 Broncco TX-6

    Any system that seeks punishment of an individual for "wrongs" committed against noone but the law itself is not interested in peace or equality, but in being able to control and manipulate it's citizens.

    Quote Originally Posted by Dirtcrasher View Post
    You've already got a sex bolt, the hard part is finding the nut it fits into :lol:

  9. #9

    Default

    Quote Originally Posted by NightBiker07 View Post
    if it was eaing dirt, it would have torn up the intake side first. definitely looks like the machinist didnt relieve the exhaust bridge. because if it was lean, it would have scuffed the other side a little when the exhaust side of the piston expanded.

    either way, this didnt happen in the cold months, then just cause problems now. everything happened right at that instant.

    I know what a lean sieze looks like...did it twice to my 300R before i discovered a tiny air leak in the damn intake...... that resembles poor machining
    thanx for all the input

    the bike didn't seize at all, only thing that gave this away was a whistle when it was running and a high idle all of a sudden. otherwise it ran just fine and started easy.
    wouldn't a inproper relived exhaustbridge cause it to seize pretty fast? I've clocked almost 30hrs on the bike since I got it.
    whenever I fire up a 2-stroker, the primitive caveman inside me wakes up and goes on a rampage!!
    My Stable O'Bikes
    -94 CR500R - BigBoreBrute...
    -00 XR650R - The Big Red Pig.
    Suzuki TS 50 - Broke piece of crap
    -93 Honda PX-R 50

    Take a look at my bikes : http://s294.photobucket.com/albums/m...tzen/?start=64
    My Youtube Channel : http://www.youtube.com/user/lauritzen2

  10. #10

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    Quote Originally Posted by morph0906 View Post
    that looks like aluminum from the piston! i would say that its from the blown gasket causing a lean condition. I have seen your vids and if it wasnt jetted right it wouldnt have lasted that long! whats the piston look like?
    I didn't take the cylinder off, gonna check around for someone to hone my cylinder first, gonna take everything apart next weekend and check for play in the rod\crank and clean everything up.
    but I looked through the exhaustport and the piston looked much worse than the cylinder.
    whenever I fire up a 2-stroker, the primitive caveman inside me wakes up and goes on a rampage!!
    My Stable O'Bikes
    -94 CR500R - BigBoreBrute...
    -00 XR650R - The Big Red Pig.
    Suzuki TS 50 - Broke piece of crap
    -93 Honda PX-R 50

    Take a look at my bikes : http://s294.photobucket.com/albums/m...tzen/?start=64
    My Youtube Channel : http://www.youtube.com/user/lauritzen2