Want to know if the previous owner has fiddled with it or not.
Pop the seat and tank off. Remove the upper engine mount brackets. Then pull the valve cover. Check the number of links between the two timing marks. I can't remember off hand how many links/pins for YZ/WR timing respectively, but Motoman 393's site (here on TT) should have details and pic's. This is all presuming we are talking about a 400/426. If you have a WR450, you will have to buy a YZ450 exhaust cam to get YZ timing.
Shift up into 3rd gear. Roll on the throttle from low rpm.
WR timing will snap off the bottom and flatten out at high rpms. All the snap will be right off the bottom. ""Bang"
YZ timing will "chug" a little at low rpm and then pull progressively harder at mid and high rpm's BrrrrrrWaaaaaaa.
It's pretty unscientific but its the difference is detectable.
just count the number of pins between the punch marks on the cams and check in ur wners manual what it should be.
The only way to tell for sure is to count pins between 12:00 timing marks on intake and exhaust cam. If you have WR timing there will be 13 pins. If you have YZ timing, there will be 12 pins. This is assuming that the original exhaust cam is in the bike.
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