Very often, it happens that the 535, which passed more than 50000 km suddenly "looses" its fuel reserves. The problem is in the electro-valve which is placed above the rear fork and is set in motion by "Fuel" switch: on the right side of handlebar. There is water and mud comin into the electrovalve through the cable entrance so after the certain time the valve gets blocked in "open" or "closed" position. In case that happens it should be taken off, (please use angled-criss-cross-screwdriver & the number 10 spanner), dismantled & cleaned carefully and thorougly. After putting it back on, the valveshould be tested by alternate switching of the "Fuel" switch. If you hear a "happy" click yoour problem is solved.