Crankcase pressure

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?

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.

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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