Aug 30, 2010 · The 290 was the best of both worlds. It allows you to be a little less on the ball as far as being in the right gear all the time because of the additional cc giving it a midsize four-stroke feel.

Jul 10, 2013 · most likely rich if the pilot is stock. A 290 will create more vacuum when the throttle is closed, thus pulling in too much fuel from the stock pilot. Is jetting still stock? Have you tried adjusting the pilot screw? Maybe try searching the jetting database for similar big bore kits.

Jul 22, 2007 · My Dad's friend and old pro Denny Swartz has a 290 kit (not sure what brand) in his 04 yz250f and loves it! In fact, he actually sold his 2011 crf450 because he preferred riding the old 290f over it. I'm pretty sure its been solid as a rock, and …

Oct 1, 2019 · I was just wondering what some peoples opinions are on the Athena 290 big bore on a wr or yz250f. Will I notice a difference in power? Is it worth the money? Is it hard on the engine?

Feb 16, 2016 · You will need to get the head ported and have bigger valves to utilize the extra cc's. I have ridden a yz250f with the 290 kit on it and it pulls great down low but signs off early. With the porting and bigger valves you can improve the over-rev.

Choice between 83mm Forged JE piston kit or 13:1 Wiseco piston kit (Stroker compatible 310cc) (add $50) , Cometic big bore top-end gasket set. We install a stainless steel Crush ring in the cylinder to ensure the head gasket seals properly. ($50)

Athena’s Big Bore Cylinder Kits guarantees an increase in performance that can be observed along the power curve, keeping the reliability at the same level of the original components. The kit includes the high-quality aluminum cylinder with increased bore, the complete piston with the piston pin and rings, and all the necessary gaskets.

Athena’s Big Bore Cylinder Kits guarantees an increase in performance that can be observed along the power curve, keeping the reliability at the same level of the original components.

Aug 24, 2008 · It has much larger water jackets and is a completely new cylinder. This make the engine run much cooler that just a stock cylinder with a big bore as they seem to run hot. I loved my Ice Cube kits I have used. They cost a bot bore, but you still have the stock parts to put back on should you desire to do so. slipdog wrote: