After (and only after) our continued and extensive development of the new G4 - 850 Summit in our Superflow 901 dyno facility for the past 14 months as well as 30 plus days in the mountains ranging from 4,000 to 11,000 feet we are proud to offer the following stock bore 850 products.  
TMS received a new G4-850 summit in early April of 2016 Directly from Ski-doo to develop a new big bore and other performance modifications that owners of new summits are looking for. We were 5 years ahead of "the competitions" big bores with our 872 Etec engine package and are way ahead of the curve with G4 products. 

    TMS has been the engine builder for the team Ski-Doo racers for the past 13 years on the western RMSHA hillclimb circuit with our engine packages producing over 400 top 3 finishes translating into great development for our consumer products. 

G4 850 stock bore package - 4,000 to 11,000 feet
-New CNC machined oem BRP cylinder head
-TMS fuel programmer (pre programmed for your application)
-Complete TMS clutch kit including ramps, extensive weight kit and secondary spring.
Detailed specs on timing offset changes and gearing requirements. 

Customers who purchase this package will get credit back if they chose to upgrade to the TMS G4 927 big bore package at a later date.

$ 850.00 for package.

    Cylinder porting gains for the new 850 engine do not justify the time or expense associated with removing the complete engine. We have spent many hours on the dyno and field testing to find only slight top end gains that do not justify the sacrifice on low end torque and throttle response (race applications are different). Piston wear is also increased with any major changes to the exhaust port on any stock bore 850 engines - simply put it is best left alone as the Rotax devoplment team did their homework with this engine!

‚ÄčTMS G4 850 Summit

Your Rotax Performance Expert       1 (507) 281 3545