The engine power is too high in the rev range for MX, ok for flat track.
Suspension,linkage change required as well as revalve and springs required for racing MX. The bike is now well out dated for racing, although very reliable and cheap to race. A great club level bike to learn skills , power needs to moved to get more bottom end for MX. Cylinder and head work required. The KTM sx65 is alot faster as the bike has a powervalve and better suspension. HGS exhaust and a vforce reed valve are the best mods for the engine, and with cylinder and head work the engine is very good for mx or flat track.
The basic bike is still a little behind the KTM sx85 in stock form but mods are easy to do on the bike.
Fitting the HGS or VH exhaust with the VHM cylinder head and special insert developed by BUD racing, the engine really performs well. Some jetting and needle changes are required for racing. Vforce reeds work better then the boysen rad valve.
Changing the suspension springs, a new linkage, and revalve to suit rider weight, the bike performs very well. The conrod weight is very heavy and needs to be reduced for top level racing. After the mods are done for racing you have a very solid bike that gives very little trouble. Overall this is probably the best mx or flat track bike as the performance is good and ongoing costs for racing can be low. This bike has much better brakes,throttle set up, rear suspension than the Ktm sx85.
Things to watch- run oil ratio at 30-1 for racing. Crankshaft oil seals wear if using some race fuels and you have to split the cases to replace them. The 2 ring piston is only good for trail riding or enduro but you can remove 1 ring for racing. The Vertex coated piston is better for racing. Overall bike weight is higher than the ktm, the gearbox is heavier than the ktm. There are areas on the bike you can reduce weight. ( gear tumbling works well for racing on the kx85) long term we will see more of KX85 on the racing seen.