I have an 1982 XR500R which has been sitting for 15 years. Was running fine when parked, only had a leaky rear shock at the time. I have pulled everything apart from this bike except the engine case and rebuilt it. New chain, wheel bearings, etc. Rebuilt all of the shocks and Carb. Runs like a champ. The clutch works fine and engages the gears 1-5 without any problems. The sprocket spins when there is no load (Chain connected to back wheel). However, when there is a load, the front sprocket does not spin, so no power to rear wheel. Any ideas on why there is no power transfer to the wheel? I am thinking that a lack of oil may have frosen something up in the transmission, but am a little confused on why the front sprocket spins without a load on it. Thanks in advance for your thoughts.