A guy I work with has an 86 xr 650 (I think), anyways it smoked like cancer patient so I rerung it and replaced the valve stem seals. The smoking is gone but now it cuts out on accell. If you take the side of the airbox off it runs like a champ so he drilled some air holes in the box and it seemed to run ok. He then noticed that air was actually blowing out of the holes he drilled. That just doesn't make since to me it should be sucking, the bike seems to run ok idles fine etc. Anyone ever run into something like this. The engine does have 2 carbs maybe one side is blowing and one is sucking???????