Fit of new YZ400F cam chain

6 replies to this topic
  • DeeCee

Posted June 02, 2008 - 07:07 AM


I have just fitted a '03 YZ450 exhaust cam to my 400. I have also fitted a new OEM cam chain.

The cam chain does not enter the teeth of the cam shafts as far as I expected - see accompanying photos.

Is this normal ?

Any advice most appreciated.

  • bluemax250

Posted June 02, 2008 - 07:14 AM


That's about what I remember mine looking like.
If it wasn't fitting on the cams properly, I doubt you could get the chain around the cams and crank sprocket.
The chain will be slightly loose until the tensioner takes up the slack.
Hope this helps.

  • grayracer513

Posted June 02, 2008 - 07:53 AM


Yes, that's normal. This was the issue that had everyone worried in the early days of this modification, but nothing bad has ever come of it.

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  • Yz400Flyer

Posted June 02, 2008 - 08:04 AM


Enjoy your new mod! Like everyone has said in the past, best mod ever for these bikes. I bump start mine just like a 2-stroke, easy to start when hot, etc... (I do have to give it a throttle of gas before starting it tho).

  • DeeCee

Posted June 03, 2008 - 12:15 AM


Thanks for your responses, they have put my mind at rest.

I will now close the engine up and hopefully have my first ride with the new cam on Friday.

  • DeeCee

Posted June 06, 2008 - 07:50 PM


I have now had my 400 running since fitting the 450 cam.

I had to change my starting technique from a hard boot to a smooth long stroke and once this was done, bike starts first or second kick as before, but with way, way less effort.

Riding showed better low end power however the real bonus is the ease of starting. This is especially relevant for me because I ride desert and inevitably stalls/falls are in awkward places in soft sand. With the original decompression/hard boot set up, starting after a stall/fall could be very tiring. Now a smooth stroke of the kick start without worrying about going past top dead centre, is all that is required. Chalk and cheese comparison !

I consequently recommend any 400/426 owners out there who have not done this modification to seriously consider doing so.

  • shrekka

Posted June 07, 2008 - 03:24 AM


Hi there
i done the same thing to my 2002 426, and it looks exactly the same as the photos.
Nothing gone wrong since the mod either
The "Yamaha YZF & WRF Performance Projects" book says do the same thing for our bikes with the 450 cam...


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