hi guys, i'm a new DRZ 400 SM owner and i must admit i am in love. the bike is great, i use it mostly for getting around my city which has a huge traffic problem. i ride it on the sidewalk, over the tram rails, off-road over the green fields between roads, anyway it's awesome. but, this being my first sumo and my first monocylinder bike, i do have a few questions and here they are: 1. what kind of oil do you use? brand and type. 2. is it worth to buy an aftermarket air filter? will there be any difference with regards to power and acceleration? 3. i would like to change the carb with a bigger one .. 39 or 41...what do you think? 4. my rear tire is 140/70/17. could i fit on a 160/70/17 on the same rim? most of the tyre manufacturers do not make 140 competitive tyres. for exemple michelin doesnt produce Pilot Power on 140, Pirelli doesnt produce Dragon Supercorsa on 140, neither does Dunlop with the D209 Qualifier RR. So, can i fit in a 160/70/17 ? 5. another problem is that the i need to get tubless tyres. is that possible with the factory Excel rims? do i need anything else? that's about it ! cheers !