Taken from CycleWorld archives:
The original use of
exhaust wrap was for cars, the idea being to keep underhood temperatures lower so the engine could have access to air that was less hot. It's hard on
pipes.
Wrap can cause excessive heat and hold and trap moisture and detritus against your
exhaust, which will shorten the life of the
exhausts
Pipe wrapping comes from NASCAR, where its purpose was to cheaply reduce temperature in well-filled engine bays. Its current use on custom bikes is a visual theme that builders apparently like, but it has no function. If you walk through racing paddocks at MotoGP or World Superbike events, you will see no woven fiberglass tape wrapped around pipes
Some years ago John Wittner (builder of Battle of the Twins
Moto Guzzis) warned against the use of such wrapping on titanium pipes, which overheat, react with oxygen, and transform into a mass of loose yellow flakes. During the two-stroke era in 500cc Grand Prix, bikes appeared for the Japanese GP with pipes insulated by various means. This was done to meet new noise regulations. Later, it turned out to have undesired tuning effects so its use was discontinued
