I have a stanley HYDROSTATIC (no shift lever , just forward and reverse foot pedal,) riding mower , looks like new , bought it used , rebuilt carb , runs great now butttttttt,,,,,when I took it out in yard for a test drive It creeps along like a snail going forward , backs up at fast . I know the linkage rod from foot pedal to tranny has an adjustable hook up @ transmission location but the rod from foot pedal is already pushing the linkage back as far as it can go now , I disconected it at the foot controll and measured it by hand and it goes as far as it would hooked up or un hooked ? ANY Ideas ?

I have several ideas, but I don't think you are going to like any of them. Fluid pressure in the forward flow is low. Possible causes: 1. Internal seal failure in the trans.
2. Trans fluid is low - has leaked out
3. Trans fluid is thin.
Any of these repairs require major transmission service or trans replacement. For the most part, Hydro transmissions are worry free. When they do have a problem, the recommended repair from Hydro is to replace the trans. They do not have a fill or drain plug, with the exception of having a vent, they are sealed. I have heard of people filling thru the vent, but not always with success and there is no way of knowing when it is full.
Sorry.