02 yz426f timing marks

2 replies to this topic
  • brewerjw1011

Posted May 01, 2014 - 02:28 PM


Hey guys i pulled my valve cover off today to see if my valves were in spec and i got it to TDC and the timing marks werent parallel to the block i lined the mark on the crank with the l mark on the flywheel and then the cam marks were off. I thought the cam marks were susposed to be parallel with the block at the same time while on TDC do yall have any ideas this is my first time adjusting DOHC engines and im puzzled any help from u guys would be greatly appreciated i kno my valve spec for the intake side is .10-.15 and exhaust is .20-.25 correct me if im wrong and when i stuck my feeler guages in there it was way off on intake and exhaust so yea im kinda confused any help from yall would be greatly appreciated thanks

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  • grayracer513

Posted May 01, 2014 - 03:17 PM


First, there are 3 marks on the flywheel.  They are clustered together, and the first two from left to right are normally connected by a horizontal that makes them resemble an "H".   These are fro ignition timing.  The third mark is TDC for the cams. 


If your 426 has the original cams, There will be an "E" and an "I" mark on each cam.  These are to align with the gasket surface on top of the head.  If it has an exhaust cam with a flyweight on the sprocket, then you need to know whether it is an aftermarket cam made for a 426, or a Yamaha cam for a YZ450.  Most aftermarket cams will have some numbers stamped on them someplace, the Yamaha cams not. 


In the case of the aftermarket cams, there is usually a mark that will align with the head at "9:00 o'clock", and another at 12:00.   The Yamaha cam is more complicated: 





  • brewerjw1011

Posted May 02, 2014 - 02:18 AM


Ok thanks that helps alot and they are the original cams ill keep you updated

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