Just rebuilt my 400ex with a new 89mm piston (10:1) and a new jug. Adjusted the valve lash to stock specs with a HotCam Stage 2. Also has a FCR-39mm carb.
After firing it up the first time this is the noise it was making. I have read up and it shouldn’t be piston slap (new piston), timing chain seems to be good. Maybe go to .13mm/.15mm valve lash? Any ideas are appreciated. I know these all have a bit of top end noise but mine seems excessive. Really don’t want to blindly tear this whole thing down again…
