Crankcase pressure

2 replies to this topic
  • RiderX

Posted June 23, 2007 - 05:49 PM


Just picked up a used '00 YZ426. There's quite a bit of blowby coming out of the crankcase vent hose. No oil, just these motors create a lot of crankcase pressure? Also I figured I'd change the oil before I rode it since I don't know the maintenance history on it and there's quite a bit of fine metal shavings in the filter and filter cavity. Should I flush the motor?

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  • 642MX

Posted June 23, 2007 - 07:33 PM


Yes and Yes.

I've always found aluminum shavings in my oil filter since the bike was new and they do create some crankcase pressure.

Most of the 426's are bullet-proof. Keep the oil fresh and the air filter clean and they last forever.

  • brolo747

Posted June 24, 2007 - 12:10 AM


I imagine the shavings you are seeing are from the clutch. Replace it with a billet one as soon as possible. The yz/f, cr/f,kx/f are all notorious for having crappy cast aluminum baskets that groove out real fast then your f-plates will lock into the basket and no more clutchy worky. So at the least replace your clutch basket with a decent billet one. has got one for around 139.99 (PE is the brand) that I have heard good things about. Otherwise you are looking at about 170 - 250 for a hinson or barnett or other name brand.

O yea and the breather tube just shoots out air... If you want to have fun plug it for a while and see what happpens. J/k:naughty: :thumbsup:

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