99 yz400f Valves

2 replies to this topic
  • ilya5903

Posted May 19, 2013 - 04:10 PM


I recently bought a 99 yz400f off of a friend of mine. Bought the bike for very cheap due to the fact that the top end is completely disassembled. it was torn apart because he had the bike stall on him one day and never start back up, thinking that the timing chain jumped a tooth he tore the bike apart and i ended up buying it... iv been slowly collecting parts to rebuild the top end and in the process of doing so i filled the intake port with fuel to see if the valves were sealing properly. I'm getting a little seepage from the valves even after tapping on the stem side to try and get them to seat. Could this indicate that the valves may be slightly bent? I also checked the valve lash and it measured within spec.

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  • grayracer513

Posted May 19, 2013 - 05:29 PM


"A little seepage" is normal. If your clearances are OK, you probably have nothing to worry about. However, because the valves in the 400 were stainless steel instead of titanium, you can lap them as a touch up.

  • ilya5903

Posted May 19, 2013 - 05:40 PM


Ok. thank you for the prompt responce. puts my mind at ease. ill probly end up lapping the valves, everything is alredy apart so why not i guess

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