Hi
I had a yse8 (it is nearly the same) and it only started cold, never when it was warm. It was after a total rebuilding of motor i found out that the top regulator in the dieselpump fastned to the governor arm had to be total closed for to start warm. When the motor got warm the metal expanding in the governor arm changed the tolerence enough to never start warm. You have to lose the governor arm from the topregulator on diesel pump and then with a screwdriver close the regulator totally. Fasten the arm again and it starts .
Per Boelskifte, June 2010