There are detergents in oil it could be from that. Not sure what happens after first going to a full synthetic either. Ive ran amsoil for years never had a problem. Only thing id suggest is maybe somehow you got water in the system? Maybe something wasn't tight when you washed it?
99 416ex
Big Gun, JE, Burgard, LSR, Maxxis, Tag, Hot Cam, PEP, Powermadd, DG, K&N and Maier
Thanks Burgard Racing, Colby (C&D Racing) and Pappy (BK Performance Coatings)
2009 Special Edition 450ER
Big Gun, K&N, Houser, Tag, Powermadd, Pro Armor and LSR
1995 TRX90
Big Gun, ITP, Tag, K&N and Blingstar