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clark4131

?'s About YZ Cam in an '05

8 posts in this topic

I'm really wanting some scary fast performance on the bike, so I'm seriously considering dropping a YZ exhaust cam in. For $100, it seems really cheap considering the rest of the goodies I've dropped into the bike already. From what I've been told, it will also make my jetting issues much less of a problem since I'm almost always riding above 4500'. I was also told that it will increase power across the board without any loss in the low end. Any thoughts on this?

I did have a couple of questions, if I go ahead with the mod...When installing the YZ cam, do I install it they same way as the WR cam with regard to the punch marks lining up at TDC as shown in the manual? If that's all there is to it, other than re-checking my valve clearances once it's installed, then it's a breeze. Now will the YZ cam tend to create tighter or looser valve clearances? Thanks to all you speed gurus out there for your wisdom :naughty: ...SC

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Install as if it were a WR cam. The sprockets are shifted for you, and the decomp pin is shorter by about 1mm.

It won't be "scary fast" compared to stock, but it will provide a noticeable improvement.

Couple it with a YZ pipe, open the airbox, and add a JD jet kit and you're good to go.

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What kind of change, if any, will the shorter decomp pin have? I've already done just about everything you can do to my WR thus far. I'm in the process of getting the Barnum's Pro airbox kit installed and I'm switching to a #100 PAJ as soon as it arrives. I also have an FMF full system with the Q2 can. I just don't want to lose ANY of the low end, so I want to be sure before I put in the YZ cam. Thanks for the info...SC

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The shorter pin allows the engine to start with the (retarded) YZ timing.

With the longer pin, it holds the valve open too long and doesn't allow enough compression to build for starting.

The only difference between the YZ and WR cam is the timing marks are rotated by one tooth and the pin is shorter. You CAN grind the pin down and rotate the cam as you would an '02, but for the $150, I'd just buy a new cam.

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Great swap, my 03 with the YZ cam is not really faster than my buddys 04 which has all the same mods as mine but no cam, it is in my opinion more fun to ride though , going from bike to bike I really notice the difference in throttle response, with the timing change the power comes on sooner with no sacrifice up top, very useable!! Enjoy.

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My buddy saw absolutely no drop in the low end.

At first he thought we had screwed something up because he felt like he was hitting the rev limiter too quickly. A quick check pinned in 5th at 81mph proved that the limiter was in fact NOT cutting in at 7k as we suspected... the bike is just THAT FAST getting through 1st through 3rd, and pulls hard in 4th.

Compared to my WR (still timed WR), the bikes are pretty much even into 3rd. Top end of 3rd the YZ-timed WR will pull away slightly, and by the middle of 4th it's all over for the stock WR.

There is NO loss of bottom end.

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