help checking oil pressure
 

ive got a 1983 kz750-k1 ltd belt drive. the other day when i went on a 2.5 hour trip my low pressure light came on as i was pulling in to get gas. this light has never come on before. i checked the oil level and it was fine. i noticed that the light would stay out if i kept the rpms above 2500. im hoping its just the sending unit thats bad. but my question is, what should the crankcase PSI be? i have a crappy Clymer manual and i cant find the specs anywhere. TY

I am not sure on the KZ 750, but my '81-'83 KZ 1000 manual states: 10w40,(refer to temperature table), 2.8psi at 140 degrees with the engine running at 3000rpm