Hi, I bought a XR 650 L '04 with 20k on it. It burns oil and backfires a lot. Its not too bad but is more than normal top up. Also if ridden on high rpm long or if in tight trails where it will overheat, the oil consumption is more. Does not smoke. It is rejetted, desmoked , with fmf muffler. I had a mechanic do a pressure test. He said that the exhaust valve is leaking. However the compression is within the proper limits. Could it be only valve seals or more ... Please comment and advise !Thank you !