450 cams in 400?

I have read that some of u that owns YZ400 have modded youre bike with 450 camshafts? Do u replace the old cam with a cam from 450?

What is the result of that and if i want to do it, what do i need and what do i think of?

I don't have the YZ 400, but a WR with the YZ 450 cam..... It was simply an exchange of the exhaust cams and also new shims..... The bike hits REALLY hard now and the starting is a breeze with the auto decompression.. You might also want to pickup a decompression level plug from the TT store, so you can remove the lever on the front of the head.....

Curt

You need the cam. You may or may not need two valve lash adjusting shims.

Roll the engine up on TDC with the cam timing marks up.

Remove the tensioner

Remove the exhaust cam and replace it with the 450 part. You have to use the "12:00 o'clock marks" on the cams to time the 450 cam because it's marked for a different head. With the intake cam still timed correctly, count 14 pins between the two 12:00 marks and button it up.

Important points:

Use a torque wrench, and use it carefully. I recommend using a torque value of 75 in/lb instead of the 86 that's called out. The cam caps can be fairly badly distorted and seize if improperly tightened.

If you leave the decompression lever in the head, you must also leave the coiled return spring on the lever to keep the lever from hitting the lifter unintentionally.

Here's a post including a picture of the correct timing:

http://www.thumpertalk.com/forum/showthread.php?p=1934432#post1934432

The result is a much easier starting bike (it will bump start easier than most two strokes)

Thank you!!!! This sounds very intresting and i think im gonna check this out a little bit!!!

It is the best mod I did to my '99 WR400. Easy fix....

Last question (i think) From wich year should i use?

I just ordered the first year de-comp cams were available. Read through the long threads and you can view all the percieved problems and fixes. I just no it was no problem in my bike:-)

I just ordered the first year de-comp cams were available. Read through the long threads and you can view all the percieved problems and fixes. I just no it was no problem in my bike:-)

I'm using an '03 with no issues.

The cam is the same for all '03-'05 models. That one is widely available, and can be bought throught the TT OEM store for less than $100 (last I looked). The '06 will fit, but has a different pn. The lift figures are the same, so I'm not certain at this point what the difference is. In any case, there are many very happy users of the '03 cam (5TA-12180-00-00).

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