Hi, my mates wrf426 has dropped an inlet valve, it appears to have snapped 2 mm under the collets. How can I tell if they are stainless or titanium.? I've not messed with many 4 strokes but loads of 2 smokers. Should I replace just the 1 valve as I have a limited budget. Piston seems ok, has a slight mark but no cracks. Think we intend to replace 1 valve, all valve seals and replace camchain. Should do the job I hope. Regards. Stan.