Hello, new to the board, first post. I am trying to sort out an oil choice for my DR650 dual purpose bike. It is a 650cc air cooled single, shared trans and engine oils. Capacity of 2.1L. But it has the SACS air cooled engine oil system similar to the GSXR's. This bike has had a very notchy transmission from new. Plus there have been reported internet failures of the 3rd gear which may or may not be oil related. I used to run Rotella T5 15w40 but have since switched to Kawasaki S4 15w50 that I scored for $7 a litre. I noticed a very significant reduction in the shifting notchiness with the Kawi syn oil. I have since depleted my stock. Does anybody have any info on who makes the Kawi S4, just for interests sake? I am thinking of going to a 20w50 oil to protect against any possible trans issues and see how the shifting is. I have heard good things about Maxima products. I can get Maxim$ Synth blend 20w50 for $10.95/L. Or Mamix Extra 4 15w50 full synth for %16.95/L which is a decent price for a full synth MC specific oil. Anther easy to get option which should be decently priced is the Mobil 1 20w50 V Twin. But I see it is not JASO certified, http://www.mobil.com/USA-English/Lubes/PDS/NAUSENPVLMOMobil1_Motorcycle_Oils.aspx. I wonder how my clutch would like it? Thoughts?