HST?/Manual?
Model year?
Total time?
Has the machine sat for a long time unused?
Has it been that way since you bought it?
Did it ever operate normally?
Is this a sudden anomaly?
How long ago did it operate normally?
You say it stalls. By "it" do you mean the engine actually stalls and quits?
Does the engine recover when you let off the clutch or HST pedal?
Is your parking brake on?
Is your 3-pt lever positioned all the way OFF.
Sorry for all the questions Jackie but we need a bunch more information than what you gave us....
Ray