HELP- need cam chain experiance for wr450

Hello- I did a top end rebuid on my 06 wr450 and i'm putting all together to find that the cam chain doesn't fit over the cam gears. The tensioner is off and the chain seems to be around the crank gear correctly and the part# is correct for the chain, also everything is stock. Isn't the cam chain supposed to be loose enough to get it over the gears until you put the tensioner on? And if so do you have any idea what i did wrong?! I'm at my wits end here and any advise is MUCH appreciated!

The chain cannot be lifted over or off of the cams while both of them are bolted in place. Instead, the chain must be positioned on each sprocket as the cams are set in place. I do it like this:

  • With the crank at TDC, set the chain over the exhaust cam, and set the cam in place so the the timing mark is aligned when the cam is rotated back to draw the slack out of the chain between the crank and cam (don't rotate the crank out of place).
  • Then position the intake cam in the center of the head, and set the chain over the sprocket so that there are 13 pins between the 12:00 o'clock marks on the two cam sprockets.
  • Roll and tilt the intake cam into its saddle and settle both cams into the head.
  • Double check the alignment of all three timing marks, make any necessary corrections, and assemble the caps.
  • Double check the marks, assemble the tensioner and check again.

The 12:00 o'clock marks should not be relied upon for timing, but they are useful when used as described for purposes of guessing the right spot for the second cam to be positioned on the first attempt.

It is possible to loop the chain under the crank so that there is a free hanging link of chain underneath the crank sprocket. If this happens, the only way to get it straightened out is to remove the flywheel (and stator on models where it bolts to the crankcase).

Thanks grayracer, i tried the same stategy you said and it still didn't work. I sat in front of it for about two hours on saturday trying to get them to fit on and i even took the stator cover back off and it looked ok from what i could see (which isnt much as you probably know!) Is it still supposed to be pretty tight when you use the method you proposed? I guess its time to pull the flywheel again and make sure all is well down there still. Thanks again

The chain cannot be lifted over or off of the cams while both of them are bolted in place. Instead, the chain must be positioned on each sprocket as the cams are set in place. I do it like this:

  • With the crank at TDC, set the chain over the exhaust cam, and set the cam in place so the the timing mark is aligned when the cam is rotated back to draw the slack out of the chain between the crank and cam (don't rotate the crank out of place).
  • Then position the intake cam in the center of the head, and set the chain over the sprocket so that there are 13 pins between the 12:00 o'clock marks on the two cam sprockets.
  • Roll and tilt the intake cam into its saddle and settle both cams into the head.
  • Double check the alignment of all three timing marks, make any necessary corrections, and assemble the caps.
  • Double check the marks, assemble the tensioner and check again.

The 12:00 o'clock marks should not be relied upon for timing, but they are useful when used as described for purposes of guessing the right spot for the second cam to be positioned on the first attempt.

It is possible to loop the chain under the crank so that there is a free hanging link of chain underneath the crank sprocket. If this happens, the only way to get it straightened out is to remove the flywheel (and stator on models where it bolts to the crankcase).

Thanks for that time saving tip :cheers:

Never thought to count the pins before installing the cams, always more trial and error. Took a couple tweaks....

Was also wondering what to use to time it if you do't use the 12'clock marks?(those are the two punch marks on the gear right?)

Was also wondering what to use to time it if you do't use the 12'clock marks?(those are the two punch marks on the gear right?)
On each cam sprocket, there are at least two, often three, timing marks. On the OEM auto decompression exhaust cams, there are two marks. Note that in their normal, timed position, the two cam lobes will point up and out, as in the picture here:

lobes.jpg

In that position, one of the two marks on the exhaust cam will be in the 12:00 o'clock position, while the other is at 9:00. The 9:00 o'clock mark is aligned with the cam cover gasket surface on the head as shown below.

camcopy.jpg

The intake cam will either have two unidentified marks, or three, one marked "E", another marked "I", 180 degrees opposite the E, and one punch mark between them. With two marks, one goes at 12:00 and the other at 3:00, while with three, the "I" goes at 3:00 o'clock. in both cases, the 3:00 mark is aligned with the head surface as was done with the exhaust cam.

It's in the manual:

http://www.yamahaownershandbook.com.au/?r=0

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