2002 YZ426 Exh Cam Cap Damage

2 replies to this topic
  • rkahan

Posted September 23, 2008 - 10:50 AM


During re-assembly the Clip got out of place and damaged its groove in the cap (very soft aluminum). When the cap would not tighten down evenly and smoothly, I removed it and found the damage. The question is can any used cap from a 426 engine work or is it a machined set to the head? Yamaha does not sell the cap separately; you have to buy the entire head/cam assembly. Appreciate the advice and if you have a source for a used cap (assuming interchangeability), I'd appreciate that also. Regards.

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  • SUnruh

Posted September 23, 2008 - 10:52 AM


engine dynamics does this kind of fixes.

as would any "GOOD" machine shop.

it is a matched set/combo.

  • grayracer513

Posted September 23, 2008 - 11:12 AM


Caps from another head cannot be interchanged, since, as pointed out, they are "line bored" while torqued in place. Engine Dynamics can indeed correct this problem for you. Any competent machine shop should be able to, but it's far better that the machinist undertaking this task be fully aware of all the issues involved with reboring the cam bore on a shimmed DOHC head in which the valve stem height cannot be adjusted.

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