Shim Bucket Help.


24 replies to this topic
  • grayracer513

Posted March 06, 2009 - 09:42 AM

#21

"a yamaha writeup" - not "Yamaha's writeup" - the bike they wrote up about IS blue and their source was supposedly Yamaha as they stated.

Hmm. I read a "Yamaha writeup" (in a reputable national publication) that said the crank sprocket on the '06 YZ450 was replaceable, also citing a factory rep as its source. Should I believe that?

  • taksx

Posted March 06, 2009 - 09:43 AM

#22

thanx brad.

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  • Frostbite

Posted March 10, 2009 - 02:46 AM

#23

The auto decompression unit activates at around 700-800 crank RPM, not 1300. It's actually possible to kick the engine too fast and cause the unit to swing out, making it hard to start. The unit should never be in effect at any realistic idle speed.

One thing at play here it that on WR's up to about '05 or '06, the camshaft itself it actually the same as used in an '03-'05 YZ450. But, because the cam is advanced relative to the YZ, a longer decomp pin is used. Because the pin is longer, it contacts the lifter at a more acute angle and under greater peak pressure. This may bear on the difference in wear between the two engines at this point.


Hey Greyracer, I spun my cam in a drill and the decomp weight swung out at a very low rpm, I would estimate about 200 or less.
A new development with my bike, my cam lobe is toast. Looking straight down at the lobe it looks absolutely perfect and shiny. Looking at it from the side, it is ground almost to a point.

I posted a new thread and would appreciate any comments from you.

http://www.thumperta...448#post7783448

  • grayracer513

Posted March 10, 2009 - 07:54 AM

#24

Hey Greyracer, I spun my cam in a drill and the decomp weight swung out at a very low rpm, I would estimate about 200 or less.
A new development with my bike, my cam lobe is toast. Looking straight down at the lobe it looks absolutely perfect and shiny. Looking at it from the side, it is ground almost to a point.

I posted a new thread and would appreciate any comments from you.

http://www.thumperta...448#post7783448

I replied to that post.

On the matter of the speed at which the AD operates, remember that cams turn at half-speed, so 700 rpm at the crank is only 350 at the cam.

  • Frostbite

Posted March 10, 2009 - 08:26 AM

#25

I replied to that post.

On the matter of the speed at which the AD operates, remember that cams turn at half-speed, so 700 rpm at the crank is only 350 at the cam.


Good point.:p




 
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