Damaged cam cap, what now ?


8 replies to this topic
  • crf450319

Posted October 18, 2010 - 05:12 PM

#1

I was replacing my cam chain for preventative maint. and was having some trouble getting the ex. cam cap to seat properly. As an end result I damaged the channel (recessed into the cam cap) that the circlip fits into.

Yamaha doesn't sell the cam caps as I'm guessing they're mated to each head, is getting a used cam cap a reasonable option ?

:excuseme:

Posted Image

Edited by crf450319, October 18, 2010 - 06:13 PM.


  • DC_Excitement

Posted October 18, 2010 - 06:21 PM

#2

i would try a used one my self, just measure the proper clearence between the cam and the new (used) cap as specified in the manual. youre supposed to use these small clay like tourque strips that go between the cam and the cap then tourque it to spec. then you remove the strip and its flattend out and there is a gauge your supposed to measure it with. all its doing is measuring the clearence between the cam and the cap and making shure it is in spec. some one on here can prolly explain it better than me. the manual isnt that bad either

  • rmcr250r

Posted October 18, 2010 - 06:34 PM

#3

I'd also check that cam for warpage. Judging by the marks your circlip left on your cam cap it might have caused one side of the cam to get tightened more than the other.

  • crf450319

Posted October 18, 2010 - 07:10 PM

#4

i would try a used one my self, just measure the proper clearence between the cam and the new (used) cap as specified in the manual. youre supposed to use these small clay like tourque strips that go between the cam and the cap then tourque it to spec. then you remove the strip and its flattend out and there is a gauge your supposed to measure it with. all its doing is measuring the clearence between the cam and the cap and making shure it is in spec. some one on here can prolly explain it better than me. the manual isnt that bad either


That's what I think I'll end up doing, the stuff you're talking about is called plastigauge & is used for checking clearances.

I'd also check that cam for warpage. Judging by the marks your circlip left on your cam cap it might have caused one side of the cam to get tightened more than the other.


I'm not too worried about warpage, the circlip is steel as is the bearing and cam whereas the cam cap looks/feels like aluminum to me. I'm guessing that between the softer metal and the recessed space that provided enough of a crushable cushion if you will. But, I'll check it none-the-less.

Thanks for the replies :excuseme:

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  • davek18

Posted October 18, 2010 - 07:17 PM

#5

I wouldn't worry at all about running that one. Just square up the groove a little. You could plastigage it to be sure but I bet the clearance would be in spec.

  • BBrown626

Posted October 18, 2010 - 08:10 PM

#6

I wouldn't worry at all about running that one. Just square up the groove a little. You could plastigage it to be sure but I bet the clearance would be in spec.


Make sure there aren't any burs sticking out too. Should be fine. It is not a bearing surface (journal), it just secures the bearing in place.

  • grayracer513

Posted October 18, 2010 - 08:43 PM

#7

The cap will have been distorted by this little misadventure, and you can take the advice given so far at your own peril. The result of having it not work right may very well be a seized cam, resulting in potentially disastrous contact between the piston and valves.

To avoid it and know that it's correct, you should send the head with both caps and cams to a shop such as EDCo. They can check and if necessary, redo the line bore at a reasonable price.

If you want to try it on your own, then you need to fit the cam to the head without the chain and check clearance with PlastiGage as described above and shown in the manual.

  • stroker101

Posted October 19, 2010 - 07:20 PM

#8

is that a hairline fracture on the upper part of the cap(in the red outline)? just below the bolt hole?

  • crf450319

Posted October 20, 2010 - 10:22 AM

#9

is that a hairline fracture on the upper part of the cap(in the red outline)? just below the bolt hole?


Nope, that's a little piece of fiber or hair ?

Edited by grayracer513, October 20, 2010 - 11:58 AM.
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