yz400f autodecompressor cam mod

sorry if this has been covered recently, this is my first time on. i was under the impression that i could order a yz450f exhaust cam and install it right into my 99 yz400f to get the benefit of the automatic decompressor. the differences are that the tooth shape on the sprocket won't let the chain sit down as far - suspect a different chain style is in the 450. the sprocket looks like it's pressed on but can't be swapped because all the decomp stuff fits with it. the lobes are narrower (no big deal) the base circle is .010" bigger, that just means a different range of shims, there's a tiny bit more lift and less dwell (the lobe is narrower and pointier) i guess that makes it a torque cam, but the timing may be different, the dots line up in a different place. any help? someone out there knows how this has been done before. i'm worried about my friends not being able to do the starting drill as we're using my bike in the supermoto team race this saturday!

Read the sticky at the top of this forum. Everything that applies to the 426 also applies to the 400. One of the guys from work did the 450 cam mod on his 99 400, and it worked flawlessly.

The biggest thing you need to know is that there will be 14 pins in the cam chain between the top timing marks on the cams. All other timing procedures are the same as what is in your manual. The cam gear tooth pitch was a concern early on in the life of this mod but has since been proven to not be a problem. Hope this helps,


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