When having a bad bowel movement with cramping my mouth starts to water a lot! i have to spit it out. last for 1-2min. happens a few times a year. ?

Nervous system: It sound like your nervous system is reacting to the stress of the bad bowel motion. How often do you have bad bowel motions? If it is only a few times a year just try to work out what sets it off eg certain foods, alcohol, stress. If it is happening more often than that you probably should see a doctor for a check up

Salivation/ defecati: Defecation is a parasympathetic response , as is salivation. In fact there is a syndrome called SLUDGE where there is massive discharge of the parasympathetic nervous system usually due to pesticide poisoning ,drug overdose of poisonous mushrooms Certain drugs like physostigmine, caffeine , risperidone, trazadone, Reglan, can indirectly affect the system . f/u/ w/ doc .