Decompression shaft doesn't fit:

5 replies to this topic
  • irok

Posted March 16, 2005 - 06:35 PM

#1 is the scoop:

I just rebuilt a wr426. I had to buy a new head because the valve dropped and chewed the old one back up. I had the decompression shaft that slides into the head you hook to the decompression cable. And I swear..that thing just doesn't fit in this head. Everything else fits fine...I mean everything. I even plugged the hole and started it and it runs good. SOOO...why doesn't that piece fit? :) I ordered a whole new assy from Yamaha and that is the same as the one I had, and it doesn't fit at all. It appears the diameter of the butterfly and shaft are just to wide. Could this be a head for a 450? Plz help, I am really wanting to ride this bike bad, I have put hrs and hrs of time getting this thing together, and this is the very last thing needing done!!!

Thx a lot.

  • Sylvain

Posted March 18, 2005 - 07:27 AM


The 2003 450 still had a decompression hole but it's plugged as the 2003 model has the autodecomp cam. The 2004 and on models, the head is machined without the hole.

At the point you are why don't you get an auto decomp cam ? No more decompression shaft :) .

  • R_Little

Posted March 18, 2005 - 07:43 AM


Yes, get the auto-d cam!!!

Everybody's doin' it.

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  • irok

Posted March 29, 2005 - 10:55 PM


Yeah...that is what I ended up doing...but now got "other issues" :naughty:

  • Sylvain

Posted March 30, 2005 - 07:34 AM


Yeah...that is what I ended up doing...but now got "other issues" :naughty:

What other issues are you talking about ?

  • irok

Posted March 31, 2005 - 05:41 AM


Sylvain...see post "Starting after rebuilt/mods" for more detail.

I started it after putting it together, and it ran for about 30 sec, and just quit...won't fire again. Just replaced plug and it was black as coal, then

There is another guy with a similar problem, and I am going to try what people have said about his. but he isn't mentioning anything about a clinkin in the rotation. It isn't everytime that is does it, about every other or every 3rd or 4th stroke. It may be the decomp cam?

Anyway, thx for the reply.


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