I know the possibilites are endless but what is the fastest way to find out HOW the water is getting in the crankcase.
In this case, its ltz 400 quad which is DRZ400 based. I know I know, Im just trying to help a friend that has spent way too much money at the dealership and still has the same problem.
It must be a pretty serious leak as the radiators are drained within 30 min.
Im thinking of pressurizing the radiators but not sure if it will help with finding an internal leak.
Head gasket, water pump seal, or rotted out side cover are the usual culprits. If you pressurize the radiators and have air coming out the spark plug hole, it woud likely be the head gasket. If you have air coming out the crankcase vent it would be a rotted crankcase cover or bad water pump seal.
Run the bike with clean oil. Ride for a half hour and drain the oil in a tall glass. Let it sit over night, the next morning look at the glass, the water should seperate from the oil and be on the bottom of the glass. If there is no water in the glass then your problem may be a head gasket.