Tuning Your TRX 2.5, 2.5R and 3.3 Engine for Best Performance The engine’s performance depends on the fuel mixture. Turn the mixture needles clockwise to lean the fuel mixture and counterclockwise to richen it. Leaning the fuel mixture will increase engine power up to the engine’s mechanical limits. Never run the engine too lean (not enough fuel flow). Never lean the engine until it begins to cut out or stall. Leaning the engine beyond the safe allowable limits will result in poor performance and almost certain engine damage. Indications of an overly lean mixture include: Cutting out or sudden loss of power during acceleration. Overheating (temperature beyond 270° F at the glow plug) Little or no blue smoke coming from the exhaust. If any of these conditions are present, stop immediately and richen the high speed mixture 1/4 turn. The engine will probably be slightly rich at that setting and you can then retune for performance. Always tune for performance by starting rich and moving leaner toward the ideal setting. Never try to tune from the lean side. There should always be a light stream of blue smoke coming from the exhaust. Before you begin tuning, the engine should be warmed up to its normal operating temperature and running slightly rich. All final tuning adjustments must be made to the engine at its normal operating temperature. You can tell the engine is running rich by noting any of the following: Sluggish acceleration with blue smoke coming from the exhaust The …