weird engine noise HELP!!!!

3 replies to this topic
  • copenhagen101

Posted March 25, 2010 - 08:35 PM


I have a 1998 yz400 that was converted to a supermoto. My vavle cover was leaking and my buddy put alot of form-a-gasket on it to stop the leak and it ended up blocking a oil port that feeds a couple of the intake valves and they got bent and stuck, i had all new valves put in and the bike was running cherry for 20 minutes then it died. its sounds like something is rubbing in the bottom end and makes it die unless u give it a quarter throttle. it might be a main bearing or the needle bearings on the crank shaft. i dont know what it is or how to check it. if any one knows could u please give me some advice. i realy appreceate it. thank you.

  • Padgett

Posted March 26, 2010 - 07:12 AM


Your not going to like what I suggest. I would take it all the way down and split the cases. Inspect every thing and make sure to replace the oil pump and clean the oil pick up and all the passeges. I bet you got some of that stuff still floating around in the bottom end and now it going to cost you some parts and time. Good luck and I hope its not to bad.

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  • grayracer513

Posted March 26, 2010 - 07:18 AM


There is no possibility that any amount of sealer applied to the valve cover gasket could have blocked the oil passage to the cams because the passages are not exposed to the cover joint in any way. The only chance of something like that happening is if a piece of cured sealer broke free, went through the pick up screen, through the return pump into the oil tank, past the feed oil screen in the frame, through the feed pump, and past the oil filter. Somehow, that seems unlikely.

Nevertheless, Padgett is correct on where you stand now.

  • copenhagen101

Posted March 26, 2010 - 11:08 AM


alright... looks like im splitting the case saturday. YAY me. thank you for your input

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