YZ 450 cam, need help

I installed the yz450 cam in my '02 wr426. With the stock cam I could start the bike, first kick, everytime. With the new cam, I'm lucky if it will start in 5 kicks. It bump starts super easy. Also, it doesn't seem to have the power it had before. The jetting is all stock, 165 main, 2 turns out on the fuel screw. The timing mark on the new cam is rotated about 1 tooth forward. Elevation: 500 feet. Plug: tan color.

Any advice is appreciated. :)

Did you check the valve clearance with the new cam? Not all cams are the exact same. Your valve clearance may be off a tad causing it not to start easily, and it seems to effect the bike more with bad exhaust valve clearances. I know from past experiences that when your valves aren't dead on the bike will be hard to start in certain cases.

As far as the power goes the YZF cam moves the power more towards the top end and takes a little away from the bottom end where you really feel it. Your bike's not any less powerfull, it's just the power is directed at a different RPM range. I prefer the WR cam timing, it feels more torquey to me.

Am I in the ball park TTers?

Hhhmmmmm.....I may have this wrong but, I thought that the YZ450 cam was to be installed in the same position as the old cam. The difference between the YZ450 and the WR450 being the exhaust cam itself not the position of the cam??

If you rotate the old cam one tooth forward then you have the old fashioned YZ timing, If you want 450 power (sort of) you Install the 450 YZ Cam itself.

In other words I think you have your cam in 1 position off, rotate it back to stock position according to the pictures in the pdf file, not the instructions.

Correct if I am wrong folks...This guy needs some verification from some one who has done this.


I put in .11 mm larger shims and it's in spec according to my feeler gauge.




I'll take the cam cover off and check everything. I used the pdf to install it but I'm not sure if I looked at the lobes after I put the cam tensioner back in. I think I'll order the next size larger shims and see if that helps.



You need to MEASURE the valve clearance BEFORE you know what to buy. I was able to use some old shims I had removed from earlier adjustments but that was just lucky. Also count the number of links between the dots on the cam. There needs to be 14.

I don't know how to post my pictures but I can E-mail you.


You can not run WR timing with the YZ auto decomp cam. Just as you can not just change the timing on the WR 450. I think that is your problem. It puts the wieght out of position making the auto decomp close at a higher RPM. Set the timing marks flat to the top of the head in the YZ position. I bet it will start for you then. Hope this helps---Mike

Superbike is right. If you want WR timing you need a WR450 cam not a YZ450 cam because of the auto decompression feature.


if you have not sorted your timing yet try e/mailing this man he put together the pdf file i folowed it and mine runs tops i had it timed yz with standard cam and lost bottom end power then put in james now which gave me back loads of pull off bottom now i have 450 yz cam HOW EASY DOES IT START kicks arse off bottom end to.

e/mail address for THE MAN yamaha.dude@just-ride-it.com

hope you get it sorted you will love it

cookeye UK :D

Good news fellow blue guys: I had put the cam in with 13 pins between the timing marks instead of 14. It starts first kick easy. Unreal power, smooth but will rip up the ground and loft the front wheel. I'm calling in sick tomorrow and going riding.

Thanks Everybody :)


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