The Yamaha VK Pro can be an excellent grooming snowmobile and is an excellent choice for a low budget operation or for someone just getting started. It is heavy, has a 156 x 20 track, 3-cylinder water cooled 900cc 4-stroke engine, Hi/Lo transmission with reverse, and has 3 carbs with carb heat. Its most glaring problem is that it dumps the exhaust on the track. At low grooming speeds under load, the heat from the exhaust melts the snow which will re-freeze in the tunnel. You'll eventually have a tunnel full of ice and will be stranded on the trail! If you didn't bring a hammer and an ice pick, you'll be walking back to the shop.
The fix for this problem is simple - just re-route the exhaust to the side as shown in the photos below. Disassemble the top of the tunnel and haul your machine down to the local muffler shop. Our shop put new pipes (stainless steel) on the existing stock muffler. It took them about 20 minutes and was $100 in October 2017. The passenger seat is above the muffler. Cut holes in the side of the seat support as needed.
The 2nd problem with the VK pro is the carbs can either vapor lock or ice up depending on the conditions of the day. Watch that carb heat valve position for the conditions and this machine will be an excellent reliable grooming sled.
TBD: VK Professional History and model year changes