I have a 2008 that I completly blew the motor up on the bottom end. I had it all put back together to stock and now oil is puking out the crank case vent tube. I noticed my air box with a bunch of oil in it and it was running through the mottor fouling the plugs and even as bad as coming out the exhaust. We disconnected the vent tube and found that to be the problem. It runs fine but when we disconnected the tuve. oil only comes out when you let off the throttle, Not when you are in it. It Does not matter if you are in the throttle half or full when in it, it is fine. As soon as you let of it pukes it, and not just a little blow by, its quit a bit. Anyone have similar problem or Ideas?

Very common...best fix is to run a crankcase vent and loop the vent line back to the case...You can drill, tap and install a fitting yourself or Muzzy makes a replacement (Teryx Billet Rocker Covers)

You can get the covers direct or through supporting vendors on this site (UTV Unleashed, UTV Crap, ect...)

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How much oil is it puking?

Even revving it up in neutral it does it on decel? or does it only do it at a high rpm going down the road?

Surely you put new rings on it while you were down there?

Did you put the little black tube back in the crankcase before you assembled it?

Alot of oil not just your typical blow by. I did not put the motor back together so i am not sure if he put the black tube on or not i would hope so. It does not do it at neutral reving up and down only when driving and only under decel. does not matter half or full throttle. Took the top end back apart and everthing looks good there nothing put in wrong or broke.

I told your buddy Justin to take a close look at the crankcases and the magneto cover. I know that both the cases and the cover were redesigned for the 09 model. I also know yours was put back together with 09 cases, using your original 08 magneto cover. I'm not sure if this could cause a problem or not, but worth checking out. I don't have any 09 motors apart to compare to the 08s that I have in the shop.

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Only doing it on decel to me sounds like weak rings... Under throttle cyl pressure is sealing the rings but when you slow down you're losing all that cyl pressure and so oil makes it by the rings.

Did he put a crosshatch back in the cylinders with a flex hone? Only need to hit them lightly as these cyls are nikasil.

i have the same problem to, after complete rebuild with new cranck new cylinders and new piston and rings , it will blow oil only under deceleration, and its a 09

and it was consuming oil since the first day, now the odo reads 2000miles and already added more than 40 quarts of oil before it blew up.

no matter how much you vent the cranckcase it will still consume oil, have to check oil level on each gas fill on those machines, strange engine design