A number of people have mentioned it - that Yamaha 485 fan. I have a 2000 Venture XL with 11,500 miles on it. I have never touched that motor. Never even fouled a plug, even when running in the spring at 45 deg! Of course it gets atrocious gas mileage - 11 mpg. But if it gets me home, I don't care how much gas it burns. Most of my riding is solo. I can't break down.
The grand plan is 20,000 miles plus, because quite frankly, they don't make "lightweight" 2 up touring sleds like that Venture XL anymore, at least here in the States. So here at the sled's half life, I'm replacing the track and all the bearings in the drive train. I'm going to bore out the motor next year. I'm basically making a new sled out of this Venture because it's such a good base machine. I'll never own another machine like it.
I have a 2005 Bearcat 570 that I bought as the Venture's replacement and to drag the dead Venture off the trail here in its golden years. That Bearcat just doesn't have the same quality as the Yamaha. But even so, I love the Bearcat. It will creep down goat paths breaking trail, it will do 80-90 mph without breaking a sweat, plus it is as good on an all day tour as a Panther. It does everything.
For solo boondockers like myself, the sport is just going the wrong way. No way am I getting a 750 lb 4 stroke unstuck by myself. At least I have half a chance with the so called lightweight 2 strokes I have now. But I have yet to get the Bearcat stuck, so I may have to edit these remarks.