yz 426 smoking extremely bad

8 replies to this topic
  • chopp123

Posted October 12, 2011 - 05:18 PM


i just got my cylindar replated and grabed a used but mint piston of ebay. new gaskets went through head checked all this thing smokes like its on fire. have torn it down twice, good compression piston fits right in cylindar cant figure it out anybody have this issue? i drained bottom end to see if to much oil not the problem goes away when warm but when u rev it its smoking. tailpipe will drip oil

  • Stinger1133

Posted October 12, 2011 - 06:40 PM


Did you check to see if the opening on the piston rings are not lined up with each other when you put the piston in ? Also make sure the oil ring is not overlapped at the seem. I read that this will cause the bike to smoke bad.

  • chopp123

Posted October 12, 2011 - 07:33 PM


the oil rings were fine but i didnt realy check when i put it together i just put cylindar back on with them 180 apart. may have been possible twice the gaps lined up but open to all opinions at his point

  • gscx

Posted October 12, 2011 - 07:34 PM


Why would you put a used piston in a replated cylinder? That logic just confuses me...

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  • chopp123

Posted October 12, 2011 - 07:54 PM


it had only about 1 hr on it dont know why guy was selling it but it was in mint shape for half the price and the owner of the bike didnt want to pay alot personaly i would have bought a new piston but this one wasnt far off.

  • chopp123

Posted October 12, 2011 - 07:56 PM


i sent it with the cylindar to the plater so it was sized perfectly i would hink but im now leaning tword maybe the gaps were to close together and letting oil through somehow only thing that makes sense.

  • grayracer513

Posted October 13, 2011 - 07:21 AM


If you put used rings in it, you were asking for this problem.

Another possibility is that the ends of the oil ring expander are overlapped. That would mean no tension on the scrapers. One other thing that hopefully did not happen is that you may have folded one of the scrapers over, in which case cylinder damage is almost certain.

  • chopp123

Posted October 13, 2011 - 03:15 PM


no the rings were installed properly after both times i put it together the problem im being told buy a motor builder is new plating needs new rings. i believe the plating is bad but will try new rings first. i have run a piston in my race bike for 2 races then used it in my practice bike for have a season in the past and never had this issue used piston and rings and a used factory cylindar. i have done that for 11 years now. ordered new rings but im sure i think i got an out of round plating job.

  • chopp123

Posted October 20, 2011 - 06:00 PM


was bad valve seals the rings were fine i new it wouldnt be the rings i have swaped used pistons for years between my bikes.

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