That's going to depend on so many different factors. People that ride in dusty conditions and keep the OE air filters get less then 1100 miles out of their engines where other that protect them with just a unifilter and quality foam filter oils ..with no other changes and average dry riding with proper service get 6000+. Modifying..even just larger or heavier tires adds load which adds wear over time. Hard riding, wet conditions, extremely cold conditions all play a part in over life. Getting 10,000+ miles out others such as Honda, Yamaha, Kawasaki, Polaris, Can Am and Suzuki is not uncommon.. however for any CFM it is a rarity. On average we see between 5-8000 miles before either the engines need rebuilding or the frames become fatigued. Again it will depend on the usage, upkeep....and a splash of luck.
