YZ 450 CAM Woes on my 98 WR400 - Help

4 replies to this topic
  • The_Missile

Posted April 17, 2003 - 10:18 AM


I need some serious help. I just got my head back from the dealer and tried to install the yz cam. But I lost the instructions and the pdf link doesnt work any more. Where is it yamahadude?

I have 14 pins between the two punch marks. Intak cam line up as per manual at TDC. Cams aligned by sight to be 'flat from right side. 14 pins, as said eralier.

I'm confused as I see a discussion on the pdf of the instructions vs the picture vs number of Pins. What is the right way.

I have a 25 clearance on one exhaust cam, and 60 on the other (I know, I know but I just whapped in a 240 from a 175 having measured a 90 clearance and now I end up with 60 clearance. What is going on ????)

So it wont start. It wont even get close.

Is the 60 clearance the problem for starting or have I done something else to screw it up. (I know I have to change the clearance but I have spent 4 weeks buggering about and wanted to get the damn thing going to see how the new cam worked)

And how can I measure 90 clearance, add 65 then end up still with 60 clearance. I know I measured right, I checked about a gazillion times because the clearance was so big.

An before you ask, yes the CAM bolts are torqued to 10nm each.

The head was cleaned and valves lapped recently. Intake clearance are spot on.

:D :D :) :D

  • yamaha.dude

Posted April 17, 2003 - 11:18 AM


If you send me your e-mail address I can send you a copy of the PDF... I don't know why the link is not working... I suppose that will give me something to do today... figure out why...

As for the clearances, I cannot tell you why it has worked out that way... it is a pretty simple system... had you measured the clearances before the head work was done... did they put the same valves back in the same places, with the same shims and buckets...?

Make sure the bottom flywheel mark is lined up as well... the cams can seem lined up, but the flywheel can be off in relation to the whole top end... The cams turn at half the speed of the crank... the crank actually does 720 degrees of rotation for every 360 of the cams...



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  • mycr500

Posted April 17, 2003 - 04:19 PM


Did you find it necessary to remove the carb in order to access the camshafts?


  • The_Missile

Posted April 17, 2003 - 07:40 PM


Its not necessary to remove the carb to get at the cam shafts.

  • The_Missile

Posted April 22, 2003 - 04:58 AM



I was measuring the darned clearance with the autodecomp in place. Ended up putting in shims .5mm too big :D so no compression. I only realised this after I had undone the top end for about the 4'th time .... I always measure clearance with the lobe vertical....in this case hiding the auto decompression thing!!

Rode th bike to work today so all is well (sort of).

Feeling kind of stupid though !! :) :D


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