BLEW IT UP!!! ??Big Bore>??

6 replies to this topic
  • dirtrocket

Posted July 10, 2003 - 03:27 AM


Hello guy's I have a short story and a few questions for a friend with an 02 WR 426.
We went on an awsome trip to the Upper Penisula of MI and put on 130 Miles the first day and 120 miles the second.
My friend Jon had a little trouble on the return trip.... Big Blue just locked up on him.
Jon is very good at maintaning his machine. It had a fresh oil change and screen cleaning, along with air filter, just before the trip. After she quit on him we checked oil, anti-freeze air and fuel. it all looked good.
Last winter the bike went into the dealer for valve adustment and tune up. The dealer said he put YZ adjustments in the Carb, cam and she was all set to scream for the summer.
Has any one had this happen?? and is there a big bore kit for the 426??

  • SFO

Posted July 10, 2003 - 03:30 AM


Is there a big bore kit for the 426?
Why did home boys bike stick?
Are you going to try and fix it or is a dealer going too?
Write back when you have more data.

  • dirtrocket

Posted July 10, 2003 - 05:03 AM


I don't know why. I told him that he should bring it in...
to find out we are new to 4 strokes and thought they weren't going to be the high maintanence of our old 2 smokers. Thats why we all bought NEW so we would know what we have and maintain them by the book.

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  • yamahasocal450

Posted July 10, 2003 - 06:10 AM


did he drop hte bike in hte water making it hydrolock... did he seize the piston making it expand.. is his jetting WAY to lean for the given altitude causing it to run extra hot... did a valve get bent and break off and drop into the combustion chamber? there is a lot of things that could have happened...good luck to your friend :) :D

  • Rich_in_Orlando

Posted July 10, 2003 - 02:03 PM


This is why I do ALL my own maintenance. You have no idea what kind of idiots they might have working on your bike. Many mechanics are good, but they aren't the ones the shop assigns to my bike.:)

  • freestyle111

Posted July 10, 2003 - 03:19 PM


Post deleted by freestyle111

  • Indy_WR450

Posted July 10, 2003 - 07:19 PM


I have not heard of this issue with Yamaha 4 strokes. Take care of the oil, air filter, jetting, coolant, valve clearances and the bike's engine will last a long time (10-20,000 miles) before needing a new top end.


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