The oem valves in the 310R heads were installed by Husqvarna with a low weight design. Unfortunately, this design lacked the strength needed under normal stress conditions to keep the valves from sucking into the cylinders and increasing their length. Eventually the valve shafts will fold over causing varying lengths and then complete failure. We had new valves made for the 310R engines, using our +hp design. They are $80 each. Robertaccio has been running them on his 310R race bike for some time now with zero issues.
Tinken, How much of this converstion applies to the '12 TXC250 and '13 TXC250R? Thanks, starting to dig our way out to spring...damn groundhog!