The engine will run best with the HH carb needle on the 2nd clip postion and a 122-125 main jet and stock pilot jet. 30-1 oil ratio is required for this design engine, or failures will occur. There is too much open space area in the crankcases as the reed valve is too far from the crankshaft in this old design engine. Stock gearing will work fine for heavier riders and lighter riders can use a 15 engine sprocket. The bike handles better when the rear is lowered 15mm. The bike suffers from bad brakes. This is the fastest 85cc bike to race, but it requires the most upkeep, and its also the lightest engine and gearbox. Best mods are HGS or VH special exhaust, VHM head and carby boring. faster riders need to mod the clutch as they slip to much. Swingarm and Fork extentions work well for big wheel riders.General problems- running more oil is required, fast clutch wear and slippage, fork seals leak easy, throttle cable problems and the brakes can be a constant problem.
2018 -2020 SX85-TC 85 – 2018 had crankcase issues, but 19 and 20 models are just great. The best 85 ever made for racing. Normal engine engine mods for power increases, exhaust pipe, head, piston, reed valve , cdi, carby mods will give the rider a massive power increase, without mods to the bottom end at all. Some riders have well over 140 hours on a crankshaft, before rebuild time. best model ever! run a 140 main jet in summer, and a 145 main jet in winter, stock gearing is very good, clutch is great.
SX105 Big Bore kit, genuine KTM parts, the best kit ever made. well designed and what a rocket! just bolt it on, easy as ! Porting the cylinder, bore the carb and you have a real rocket! KTM really have a great design. Super FUN to ride, and seriously fast. ( the cylinder can easily been seen as different to the 85, so the 105 cant be mistaken for a 85.) Brayden Plath and Ky Woods are both riding the 105 , ask them why and they will grin big time, the bike is a blast! KTM engineering at its BEST!