Auto Decomp Cam and YZ Timing



14 replies to this topic
  • jchantzWR400F

Posted February 12, 2004 - 08:47 AM

#1

If I were to go to the auto decomp exhaust cam in my 99wr, would I set it up for yz timing just as I did my stock exhaust cam (12 pins between 12 o'clock timing marks on each cam)?

  • tcmII

Posted February 12, 2004 - 11:13 AM

#2

There are three things to consider:

1. The auto decompression mechanisim is part of the cam and by default it has it's own timing. Bumping the WR cam for YZ timing would change the timing of the decompression, and possibly affect your ability to start the bike.

2. If you start with a YZ cam than item one can't be a problem.

3. According to previous postings and installation instructions for '03 Yam cam (PM and I can send you a copy)the timing marks on the '03/'04 Yamaha cam does not relate to the timing for the 400/426 models.

There is a HUGE thread on the YZ side that covers this in great detail. Search for "yz 450 cam mod - please read". You will find more than you need.

  • Guest_Guest_*

Posted February 12, 2004 - 11:30 AM

#3

Use a WR450 cam if you want WR timing, YZ if you want YZ timing. :)

  • jchantzWR400F

Posted February 12, 2004 - 11:57 AM

#4

There are three things to consider:

1. The auto decompression mechanisim is part of the cam and by default it has it's own timing. Bumping the WR cam for YZ timing would change the timing of the decompression, and possibly affect your ability to start the bike.

2. If you start with a YZ cam than item one can't be a problem.


Well, isn't the exhaut cam identical from 98-02 on all yz's and wr's. I thought that cam was just retarded 1 tooth for the wr's. This subject makes me feel like I'm retarted at times.

  • jchantzWR400F

Posted February 12, 2004 - 11:58 AM

#5

Use a WR450 cam if you want WR timing, YZ if you want YZ timing. :)


Can it be that easy. If so, how many pins between 12:00 timing marks if I go with a yz cam?

  • tcmII

Posted February 12, 2004 - 01:18 PM

#6

The whole idea that you can re-time the WR cam to YZ timing relies on the cams being different. The assumption is that the cam grinds are the same from WR to YZ, but the cam gear markings are different, about one tooth. This allows you to re-time your WR to YZ.

Now in '03 Yamaha adds the auto decompression to the 450. Using the same approach you should be able to re-time the WR450 to the YZ timing, BUT you can't forget about the auto decompression. As I pointed out in my earlier post the auto decompression device is part of the exhaust cam and by default has it's own timing.

By changing the cam timing you will also change the decompression timing. It is my guess that when you change the auto decompression timing you may have trouble with starting. :)

So to the post above, when using an auto decompression cam pick one. WR timing, WR cam. YZ timing, YZ cam. :D

  • tctrailrider

Posted February 12, 2004 - 03:10 PM

#7

By changing the cam timing you will also change the decompression timing. It is my guess that when you change the auto decompression timing you may have trouble with starting.



Correct. Without the decomp feature the issue was 12 or 13 pins. With the auto decomp cam you either buy the WR cam or the YZ cam. You cannot rotate it one tooth and expect it to work correctly.

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  • tcmII

Posted February 12, 2004 - 03:21 PM

#8

Thanks for the having my back, I don't know how may pins you have to move to change the WR to YZ timing (haven't got to that mod yet). It's just important to know that '03 and later WR can not be "YZ" timed with out a new YZ cam.

  • John_H

Posted February 12, 2004 - 03:58 PM

#9

First, I went from 12 to 13 pins when I switched to YZ timing. Then when I put in the new YZ auto decomp cam it was 14 pins. The pdf installation file had a really good picture. I probably have one at home as well. I'll post it when I get off work. :)

  • John_H

Posted February 12, 2004 - 09:12 PM

#10

This guy posted the pdf file:


HERE IT IS

Here's my pic.

Posted Image

Hope this helps. :) :D :D

  • MN_Kevin

Posted February 13, 2004 - 03:03 AM

#11

Well, isn't the exhaut cam identical from 98-02 on all yz's and wr's?



No, BUT going one tooth on the WR cam was as close to mimicing the YZ cam, without buying the YZ cam.

  • jchantzWR400F

Posted February 13, 2004 - 04:09 AM

#12

OK, so according to the info, if I want to keep as close to yz timing as possible, I buy the yz450 cam. Then, during installation, I make sure that there are 14 pins between the 12:00 marks on the intake and exhaust cam.

Sound right to everyone?

  • John_H

Posted February 13, 2004 - 09:23 AM

#13

worked on my bike. :)

  • ChrisG

Posted February 13, 2004 - 11:52 AM

#14

1) YZ timing = YZ 450 exhaust cam.
2) 14 pins between intake cam timing mark (while at TDC) and exhaust cam timing mark on new 450 autodecomp cam.
3) It takes some time, but read the YZ 450 cam mod thread for valuable information and feedback from those who have gone before us.
4) Print out the 2 page PDF which contains instructions and a picture of what the set up should look like.
5) Get Vibeguy's decomp plug.

  • Matt96xr6

Posted February 13, 2004 - 08:43 PM

#15

Keep in mind that the YFZ guys have been timing their stock cams to the stock YZ specs without issue on the decompression timing.

YFZ CAM MOD




 
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