Why is the exhaust on my motorbike burning red hot?

The most likely cause is that the motor is running very lean. Make sure that all of the componets for the air intake system are connected and not leaking. This can happen if you have changed to one of the new high flow air cleaners like K&N. This causes the air/fuel mixture to have too much air and not enough fuel (lean). If you can adjust the carb, then make it richer.