WR cam timing


1 reply to this topic
  • DFuller

Posted February 15, 2009 - 06:00 AM

#1

I have heard of some people changing the cam timing on their yz400 to wr cam timing. I was just curious about the reason for this and if it is better for the machine and if so, is there any one out there that could give me the stepps on how to complete. Thanks, Darren

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  • grayracer513

Posted February 15, 2009 - 08:12 AM

#2

This works on the older engines that don't have auto decompression only.

Basically, the cams in the WR and YZF models had the same profiles, they were just timed different. The difference adds up to a higher revving, more powerful engine on the YZF, and an engine in the WR that runs more smoothly at low rpm and has a bit more low speed torque. You might like the WR timing if you are primarily a trail rider working in very tight stuff, or just don't ride very aggressively and don't really wring the bike out that much. You will loose some snap from mid range on up. "Better for the machine"? No. No difference one way or other, really.

Basically, all you do is advance the exhaust cam one tooth. Line the engine up at TDC, remove the tensioner, find the "E" mark on the exhaust cam and make a mark with Sharpie one tooth clockwise from it. Lift the cam out of place to lift the chain off the sprocket and rotate the cam one tooth counterclockwise from its original position and set it back in place so that your new timing mark is now lined up with the head surface, and the "E" is one tooth farther advanced, forward, to the left, counterclockwise from the original factory timing.

Be sure to read the manual regarding handling the chain tensioner, and be very careful with retorquing the cam saddle cap.





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