98 yz400f engine noise

4 replies to this topic
  • nopremix

Posted March 24, 2002 - 07:25 AM


Has anyone had a problem with an engine noise that is hard to diagnose. It sounds like piston slap that gets louder as motor revs up. To date I have done the following with no success: -Changed piston rod, new piston/pin/circlips, checked measurement of the cylinder, new cam chain and adjuster,checked valve clearence, visual check of all bearings, gears and clutch assembly. I have not replace any bearings because they all felt ok when I inspected them. I am totaLLY STUMPED. :)

  • freestyle111

Posted March 24, 2002 - 10:03 PM


if you search archives you will find a ton of post regarding 98wr400 engine noise.you can stop wasting your $ the noise is normal.

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  • nopremix

Posted March 24, 2002 - 12:12 PM


Freestyle111,thanks for your thought. I will check out the archives, but I bought this bike brand new, and this noise is way to loud to be normal.

  • sirthumpalot

Posted March 24, 2002 - 04:35 PM


I'm stabbing in the dark here, but have you checked the key on the counter balancer to make sure that it's tight? Some of the earlier models had a problem where the key would loosen over time and the loose counter balancer would cause a loud noise. I have not dealt with this personally but I've read about it on this message board. Maybe the search will turn up something useful with more details. I hope this helps.

  • nopremix

Posted March 25, 2002 - 03:15 PM


Yep, I am going to try looking at that as soon as I get this darn cast off my arm. ( that is a whole other story) I found the discussions about cb gear keys thanks to freestyle111's suggestion. Thanks for backing up the idea.

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