Motorcycle Repair: Oil leak 1988 GSX750ES, countershaft sprocket, power stroke

Question
Hi Collin, I have an '88 GSX750ES that is losing oil around the countershaft sprocket area.  I have cleaned it as well as possible, the leak doesnt't appear to be countershaft seal.  The possible culprit is what appears to be the oil pressure (or possibly temperature) sender immediately behind sprocket.  Can I take this out and make up a new gasket without draining oil?  Related, kinda, how much is too much crankcase blow by?  At idle, while warming, there is enough to feel at perhaps 4 inches above oil filler.  If engine is revved, there is less blow by.

Answer
The sending unit should come out and have some type of gasket.  As for the rest of your problem u weren't clear enough.  What do u mean by "blow-by"?  Dont get me wrong, I know what blow by is, but I've never heard of "feeling" it or "seeing" it for that matter.  Blow by is when oil comes past the piston into the compression chamber and is then burnt with the fuel "power stroke" of the motor.  Fouled plugs is usually a sure sign of actual blow by.