TMS 927 Piston
The new TMS G4 -927 piston is a completely new product developed exclusively by the crew at TMS. Building a new state of the art piston is a major undertaking of both time and expense but worth every dollar when it comes to offering the best product available. The 927 piston undergoes 11 different CNC programs in our machining facility before getting our exclusive dome and skirt coating applied.
The major benefit of our exclusive 927 piston is that it is a CAST ALUMINUM DESIGN with specific metallurgy content. All oem snowmobile companies use cast aluminum pistons in their two stroke products for a reason. There are a select few "claimed" engine builders that utilize problematic forged piston (wiseco) designs for the simple fact that all it takes is a phone call to order a 20 piston run designed by the help desk at a piston company and start marketing a "developed big bore product".
Forged design pistons for 2-stroke engines (especially large bore applications) are the worst choice possible as they fail because of their uncontrolled expansion characteristic, If the piston itself doesn't seize the locator pins are the next to fail. People continue to try to remedy the problems with this design by drilling oiling holes as well as other "band aid" fixes just creating more issues. We have pallets full of failed forged pistons from previous rotax (standard and big bore) applications that have ended up at the shop after owners have learned this the hard way.
At TMS we are so advanced on the development of piston and ring combinations for our big bore packages that we have spent the last 14 months testing and working to free up extra horsepower and efficiency that we now exclusively offer our two ring pistons with specific upper and lower rings, each with different tensions and design characteristics.
A huge amount of R&D time went into the weight and piston balance with both piston and pin weights going into consideration to make the 927 run smoother and spool up faster than the stock 850 engine. After logging over 800 extreme mountain miles on one of our shop 927 engines it was inspected and the bore, piston and rings looked as new.
Your Rotax Performance Expert 1 (507) 281 3545