TOPIC:

If it was my bike, I would replace the oil (with cheap conventional stuff) run the motorcycle up to temperature for a bit which will help evaporate water in the crankcase, drain the oil again and replace with the good stuff. But I may be wrong.

thanks for the advice exactly what i am planning to do i may also drop the sump to see if there are any deposits in it, i am not keen because i think there may be a world of pain coming my way trying to undo bolts that may not have not been touched for 35 years but surely this is the joy of owning a z13

Dropping the sump isn't horrible, if I remember correctly. You may have to drop the exhaust as well, which might be the hardest part- I think the sump bolts are all allen heads, which make it easy, and that whole area is soaked in oil anyway, so of the entire engine, those bolts are the least likely to be frozen.

Be prepared for an absolute mess, though. Even when you drain everything, there's still a bunch of oil left in it. Were it me, and the engine was still in the bike, I'd just run a couple oil changes through it and call it good enough, but you do what you think is best.

In my humble opinion, if you haven't run the engine up since the discovery, then the water (if any) will have migrated to the bottom of the oil pan since water is heavier than oil, and should find itself at the drain plug. If you pull the drain plug and start draining the oil and you get water first, then drain the oil and while the plug is still out, add another liter of oil to wash/flush out the remainder of the dirty oil, then replace the plug and top up with fresh oil and run up the engine to operating temperature. You can then pull the dipstick and check the color of the oil. If it's milky white then there's still some water in the crankcase, so dump the oil again. I don't see any reason to pull the oil pan.

The big question is how did the water get in the air breather box in the first place. You would have had about 5-6" of water in the airbox before the water would have flowed down the vent tube? Are you missing the top cover or is the gasket missing? Something's really not right if it was sitting and got that much water in the airbox.

Thanks Kawboy
you are correct in that the top of the air box was not installed obviously my own fault i had the bike in a garage for a while and was working on it since it came back from there it has been under cover outside and i hadnt refitted the top of the air box as the cover was allegedly waterproof but you live and learn

When i dropped the oil the water came out first followed by a steady flow of oil so my bike being an A1 it would appear that the water had dropped to the bottom of the sump near the front of the engine which is the lowest point, does the oil pick up protrude into this low point near the sump plug?