Does this cylinder need bored? (pic)

Discussion in 'General Support' started by eodbrad, Mar 14, 2010.

  1. eodbrad

    eodbrad New Member

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    took the head off today and sure enough it looks like the exhaust side of the piston head melted slightly and left some material on the cylinder wall. i didn't see any score marks or cracks in the cylinder. I have a cylinder hone, will running that through the cylinder to remove the material stuck to the walls be good enough?

    [​IMG]

    Photo of the Piston.

    [​IMG]
  2. yb200

    yb200 New Member

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    take it to a shop and have it measured it might be out of round and by the looks of that piston id get it bored
  3. eodbrad

    eodbrad New Member

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    yay, just what i didn't want to hear. lol. have a 66mm piston and such ready to go. but i'll get it measured and see what they say...since i don't have a bore measurement tool. Just not sure of a shop around here. We have a Honda Dealer in town..but not sure if they do that sort of work.
  4. yb200

    yb200 New Member

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    do a google search or a builder on here can bore it for you
  5. brandoz28

    brandoz28 Member

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    if my cylinder looked like that, i'd have it bored for sure....
  6. blasterfreek30

    blasterfreek30 New Member

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    by the looks of that piston......yea that cylinder needs to be bored
  7. super noober

    super noober Can't Stop, Won't Stop!

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    thats pretty nasty man, get it bored.
  8. 98blaster+4

    98blaster+4 New Member

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    why did you pull the head off did it still run?
  9. Norm43920

    Norm43920 New Member

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    Yikes ! :O That piston deff looks F'd up. Was it pullin air or what ?
  10. little3mil

    little3mil New Member

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    get a bore/hone and new piston its cheap and if you tune/install everything right it wont blow up again. I found a local speed shop (for cars) and they bore/honed perfectly for close to nothing in one day.
  11. eodbrad

    eodbrad New Member

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    it wasn't running when i pulled it apart. died a couple weeks ago..and finally got all the parts together. put it back together tonight... i honed it only, that smoothed it out very nicely, decent crosshatch pattern, put it all back together and she fired and ran on first kick.

    checked the jet it was a 300, downsized to a 260. only let it idle to warm up..shut down to cool off...warm up...cool off and it was dark out gonna do rest of burn in tomorrow.
  12. Brute71

    Brute71 New Member

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    im guessing you had old gas in the tank when it blew up?
  13. eodbrad

    eodbrad New Member

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    nope...we emptied the fuel and filled with 100oct.
  14. Brute71

    Brute71 New Member

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    damage like that is usually caused by detonation. I'd figure out what caused it before it happens again.

    With your setup, some 91-93 octane premium would work just fine unless you are using a high comp head.
  15. eodbrad

    eodbrad New Member

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    Yea...have to pull the carb apart and ensure the pilot jet is clean and clear. it won't idle at all right now even after 15min warm-up. (it did before, but only after warmed up) to maintain an idle w/o managing the throttle i open the choke just a wee bit and it will idle.

    32/1, 100oct fuel, wiseco piston/ring (new), vforce 3 reeds (new) 260 main jet. (new) old jet was 300...and also injection oiled.

    I'm getting a strange noise now...sounds like detonation. i'm running a platinum ngk plug...gapped properly. i didn't change any tolerances.
  16. brandoz28

    brandoz28 Member

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    if you honed it you DID change the tolerances, honing takes meat off of the cylinder walls, you're probably hearing piston slap.
  17. samolia

    samolia New Member

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    damage like that isnt caused from detonation, its caused when a piston ring gets caught on the exhaust port
  18. eodbrad

    eodbrad New Member

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    lots of questions folks. i am greatful for the advice and sharpshooting. it's a learning process all in all. i don't mind learning by error, hopefully i can glean info here for some do's/don'ts.

    i suppose i did change the bore slightly. i can't be much more than 66.5mm if that. kinda been hesitant to go ahead with a bore tool. (175$) i still haven't found a shop in town that does it. we have drill press at work..etc. if i had the tools i could probably do it myself at work. everything is a lil far from where i'm at....so to have the tools to do it myself would be great. can't be to difficult with the proper tools.

    1)Good places to buy a new cylinder+head? (just in case i don't track down the problem in time)
    2)not getting much 'smoke' when at idle. or when i open it up just a touch (still in ring settling stage)
    3)is it possible someone milled the head a touch? the lip on the head has got to be 1mm or less. it is a very very slight lip. (not sure on what stock would be)
    4)if there's an exhaust port problem, that would mean i should look and dremel the edges of that port slightly to ensure smoothness and no cylinder intrusion?
  19. super noober

    super noober Can't Stop, Won't Stop!

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    1) ebay is a good resource for used parts or a builder on here can certainly help ya out.
    2) i think a 260 is way small for your mods i like teh sounds of teh 300 better, why did you remove the 300? was it loading up?
    3) entirely possible someone milled the head to gain some compression, a stock head has a decent lip it sounds like yours does not.
    4) you can get in there with some fine sandpaper and make sure all the edges are silky smooth.
  20. Brute71

    Brute71 New Member

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    the crown of the piston melted causing material to freeze the rings in place. If the ring would have caught, there would have been a ton more damage to the cylinder, piston, and ports. There would also be a broken ring.
    bag0b0nez likes this.

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