Whenever we at He-Ja Motortechnics tune-up the Yamaha YZ85 to give it more torque and top end, we normally run into problems later with the clutch slipping trough.
It occurs that the normal package can not handle the improved capacity (27 brake horse power on a accelaration-test).
Among other this came known to us after tuning bikes for riders like the Swedish aces Philip Thuresson and Tom Johnson among others.
After this problems came to the light, we modified the whole thing in a proper way and succeed in manufacturing together the solution, by the use of 8 friction plates with 7 steel plates.
Furthermore we provide the housing of the clutch 12 extra holes for a better run-through of the oil which helps to cool down the hole set.
The entire unit can be fitted in every modern 85cc Yamaha with the use of a new inner house and press-plate. The existing clutch-springs can be used without any problems.
The old parts can (if in a good condition) be exchanged apart from the friction plates.