YZ/WR cams, is there a differance?
Posted March 06, 2005 - 01:31 PM
Posted March 06, 2005 - 02:45 PM
The only YZ cams you would bennifit from are the new ones w/ auto decomp in them...
Posted March 06, 2005 - 09:05 PM
Posted March 07, 2005 - 03:41 AM
Posted March 07, 2005 - 11:55 AM
Posted March 07, 2005 - 02:26 PM
Posted March 07, 2005 - 07:23 PM
If you do, then you cannot change the timing by rotating the cam (you are actually retarding the timing, not advancing it).
On the 250s, you need to buy the YZ cam or the bike won't start properly.
Posted March 08, 2005 - 06:57 AM
Good point, Wheelsup.
Retarding the exhaust lobe will narrow the separation angle and improve top end, since the exhaust event occurs first.
I wonder if anyone has gone the wrong way, or, if anyone has experimented with the intake timing.
Is there any hidden low end torque available that we don't know about?
Posted March 08, 2005 - 11:27 AM
Posted March 12, 2005 - 10:32 PM
Posted March 12, 2005 - 10:47 PM
This is more often than not mistakenly referred to as "advancing" the timing, but it is in fact retarding it, holding the exhaust valve open longer, which has the effect of increasing the "overlap".
Increased overlap allows the exiting exhaust flow to assist in scavenging fresh fuel/air during the intake stroke.... not unlike a 2-stroke.
Some TTer years ago said that the YZ was advanced (we all know that advancing timing increases power, right? ), and ever since then it has been repeated.
Posted March 13, 2005 - 04:57 PM
Ya it is a wr426, i should have notted this in my first post. Just wondering about loosening off the cam chain to advance the cam, is there a special trick on doing this? Also is it going to be a noticeable change in power delivery?
D/C, I had a WR426 that was YZ timed and I now run a WR450 that is WR cammed. I did buy a YZcamshaft for it, but after giving it lots of thought (and remebering how the 426 ran) I decided that me, trail riding, the WR cam was much better suited for me. I had the loss of low end, and the rela hard hit on the top, made nice power, but it was abrupt. Now with my "WR" timed 450, the power is nice and even, all the way. Makes it so much eaiser to ride trails. But some folks just like bragging rights of the extra power and can work around it. I did manage it OK also, but lower riding speeds (tight stuff) the WR exhaust cam or WR timed engine was best for me. If you race it on a track, or open desert, the YZ timing may be for you. Nice thing about chaging timing 1 tooth, you can undo it if you dont like it. Try it out