Info I needed to adjust successfully my valves, thx a lot

2 replies to this topic
  • arnego2

Posted June 08, 2009 - 12:20 PM


Hi Guys
I just finished the valve adjustment, finally, changing the valve shims from one to another. As I did that I moved the crank and the exhaust cam moved out of its range. So here in the thumpertalk I found the best details for me, best help thanks to all people with gave those details I did need. Also look here Checking & Adjust Valve Clearances even if it is a 250F and I have the 450F.

Big help was this:

...the manual is wrong. In the picture it shows 7 full links in-between the two cams. There is only suppose to be 6 & 1/2. After I made the change it started right up. Set the crank at TDC, and align the 9:00 mark on the exhaust cam and the 3:00 mark (I) on the intake with the top surface of the head. Back all 3 shafts up about 3 degrees, and slowly roll the crank forward to TDC again. Check the marks for alignment.

Thanks also to grayracer513

Once this is right, if you are working on a 400, 426, or 450, you'll notice there are 13 pins between the two 12:00 marks. If it's 12, either one of your cams doesn't really line up, or your bike is really a YZ250F.

The "H" is a test reference point for checking the ignition timing with a strobe light. "I" is TDC.

This was important for someone like me, I did work as a mechanic but that was about 25 year ago. Also in my case the intake marks were off by one about hour and the detail of the 6.5 links between the cam chains did the job, saved my ass :thumbsup:. Last thing I had to learn is that the chain spanner is important too. So thanks to all giving the info using the screwdriver to turn it in did make a huge difference in friction the engine has to go through; less friction less heat.


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  • grayracer513

Posted June 08, 2009 - 01:09 PM


Here we go again withe counting pins between cams. It's the wrong way to time them.


  • arnego2

Posted June 08, 2009 - 01:56 PM


Hi there
I did not say to time it that way, just in my case, and I'm sure for others too who have the idea of shimming their valves themselves. Additional info like the pin count can help. Well in my case it did and I don't believe to be the only one. What made me write this thank you note is the fact that I needed about 3 hours to pick up those info bits from several contributors. I don't think any harm is done by saying thx to all; including you by the way :thumbsup:

I did try to position the cams over those marks and was one off. I than tried the angle of those cams, putting them in an equal angle, so I was one tooth over in the other direction all in all I went through about 5 different positions and the pin count did it for me.

The reason I went through all the hassle is that cold start was becoming more difficult. All valves were out of spec no. 1 was 0.08, no.2 the same and no.3 had 0.20 + now I got no.1 at 0.18, no.2 at 0.13. and no.3 at 0.12 that seems better to me. I rather have them clicker away than dropping of onto the piston, seems healthier to me.


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