2013 YZ450 burning oil after new top end?

I recently installed a GYTR head and cams with a GYTR hi-comp piston. The bike has ran great for the first 5-6hrs. This weekend though the bike started giving a pretty good puff of smoke after idling for a bit then whacking the throttle... obviously something is wrong?? Why would the bike hardly burn any oil during break in, and several rides thereafter,  then suddenly start? Just looking for some input before I tear the bike apart to investigate?

Usually, rings cause smoke under an operating load, and will smoke pretty much continually while on the gas.  If the smoke is only the one puff after it idles (or sits) awhile, it points to the valve guide seals rather than rings.


Any number of reasons why it would suddenly start that.  The head gasket can leak oil into the chamber, but it's not likely to do that without having other symptoms, like coolant loss.

Thanks for the input grayracer. As far as I can tell it doesn't burn oil under a constant load, just after idling or sitting. It gives a pretty good puff of greyish black smoke. Coolant lose would show up as white smoke or in the oil making it frothy and milky right?

Coolant makes steam, not smoke.  Steam vanishes into the air, smoke has to drift away and dissipate. The smell is distinctively different, too.  Smoke smells like burning oil, coolant steam has a kind of peppery smell.

Understood. When I get the top end apart I suppose I'll know more. Thanks for giving me a direction.

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