WR450f timing chain & cam orientation - Is it correct?


9 replies to this topic
  • Zdirt

Posted May 03, 2007 - 09:13 AM

#1

I've been helping a friend shim the valves on his 2004 WR450f. I didn't get involved until after he'd torn it apart but we tried several different locations for the cam sprockets wrt the timing chain and finally got it to run (sounds good) with the following orientation (see pics):

chain:
http://www.putfile.c...php?img=5375479

Is this 13 links? Am I counting correctly or not?

lobes:
http://www.putfile.c...php?img=5375477

Question is - is this correct? The engine starts up with ease and sounds great when running but when the throttle is dropped the engine speed seems to drop rather quickly (almost like it has a brake on it). Is this how it should be?

My bikes (CRF250X) engine slowly goes back to idle speed when the throttle is let go.

Another question: There are three marks on the wheel for TDC - which one is correct to use on the WR?

TIA

  • Zdirt

Posted May 03, 2007 - 10:17 PM

#2

OK - the quick engine deceleration seems to have been due to the cam chain tensioner being too tight (i guess).

But I am still looking for some confirmation if the orientation of the cam sprockets if correct or not for the wr.

  • jbrooks26

Posted May 04, 2007 - 04:13 AM

#3

No, you are not counting correctly. You would be counting the pins between the top timing marks on the cam gears. I am not certain if the cam you are running is for a YZ or a WR? The bottom line is this, if your timing marks line up with the head with the I in "HI" on the flywheel lined up to indicate TDC then you are good to go. Looking at the picture and the fact that you say it runs good I would say that you are running a YZ cam and this would be correct timing. This is pure speculation though, all you really need to worry about is the timing marks on the outer edges of the cam gears lining up with the head surface at TDC. Hope this helps.

Josh

  • Fullbore4

Posted May 04, 2007 - 07:19 AM

#4

If I remember correctly its the 3rd I mark as you rotate the wheel. There are better pics in the following thread:

http://www.thumperta...0&highlight=cam

  • Zdirt

Posted May 04, 2007 - 08:28 AM

#5

No, you are not counting correctly. You would be counting the pins between the top timing marks on the cam gears. I am not certain if the cam you are running is for a YZ or a WR? The bottom line is this, if your timing marks line up with the head with the I in "HI" on the flywheel lined up to indicate TDC then you are good to go. Looking at the picture and the fact that you say it runs good I would say that you are running a YZ cam and this would be correct timing. This is pure speculation though, all you really need to worry about is the timing marks on the outer edges of the cam gears lining up with the head surface at TDC. Hope this helps. Josh


The bike is stock (WR cams). I finally understand the counting thing and from this there are 14 pins between the top cam lobe marks:

http://www.putfile.c...php?img=5381247

does this mean that the exhaust cam should be rotated CW one tooth?

I guess i'm a little surprised the bike runs at all if the timing is out like that.

Does anyone have a good (or bad) picture of the timing marks and which one to use? I am still a little confused here and do not have the bike in front of me.

Thanks for the responces so far. :applause:

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  • jbrooks26

Posted May 04, 2007 - 09:47 AM

#6

If this is a stock motor then forget about counting the pins. Use the timing marks at 3 o'clock on the intake cam and the 9 o'clock mark on the exhaust. Line these two marks up with the top of the head at TDC with the chain tight and you will have a properly timed WR. The counting of the pins was used for converting the WR to YZ timing, which you can't do on the bikes with auto decomp without changing the cams out anyway. Just use the timing marks and you will be good to go.

Josh

  • Zdirt

Posted May 04, 2007 - 09:55 AM

#7

If this is a stock motor then forget about counting the pins. Use the timing marks at 3 o'clock on the intake cam and the 9 o'clock mark on the exhaust. Line these two marks up with the top of the head at TDC with the chain tight and you will have a properly timed WR. The counting of the pins was used for converting the WR to YZ timing, which you can't do on the bikes with auto decomp without changing the cams out anyway. Just use the timing marks and you will be good to go.

Josh

Thanks Josh! :applause:

From what you've said I guess the bike should be correct.

Z

  • jbrooks26

Posted May 04, 2007 - 09:59 AM

#8

I don't know if it is very accurate or not, but the picture in the 04 WR450 manual shows 14 pins between the timing marks. It is a drawn picture, so accuracy is not guaranteed. However, if your marks line up with the head then you will be good to go. That would explain why it starts and runs good with the current setting. Keep it dirty side down!

Josh

  • Zdirt

Posted May 04, 2007 - 12:55 PM

#9

Josh - you've been really helpful.

Yeah - i looked at the drawing in the manual as well ... it not being a picture made me a little apprehensive to put much faith in it.

The manual states to line up the "I" mark to get TDC but I am pretty sure when both indicators on the cam gears are even with the head casting the bike is lined up w/ the "H" mark??? What is the "H" mark used for? Is it if you have a YZ?

  • jbrooks26

Posted May 05, 2007 - 10:44 AM

#10

No, the H is used with the engine running using a timing light. You need to set the engine at TDC before you even look at the marks on the cam gears. Do not use the dots on the cam gears to determine TDC. If you are not certain of TDC, you can use a drinking straw stuck into the cylinder through the spark plug hole. Simply turn the engine over until the straw is at it's highest point, then you will be sure you are at TDC. Without the timing chain, both cams will spin independant of the crank and each other. You must set the engine at TDC, and then line up both of the timing marks with the edge of the cylinder head, noting that the lobes are pointing outbound. I hope this helps clear up the confusion, if not I will try again.

Josh




 
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