This is the Traxxas TRX 3.3 Multi Shaft Racing Engine with Pull Starter. This version includes threaded crankshaft inserts for short and standard applications. COMMENTS: Other versions of the TRX 3.3 engine include; #5404 Single Shaft without Starter, TRAG5404 #5406 Multi-Shaft without Starter, #5407 Single Shaft w/Recoil Pull Starter, TRAG5407 Some notes on slide valve and rotary carburetors. Rotary carbs offer a larger response in the middle of the power band. This works well for off-road applications when throttle response must be varied. Slide Valve carbs provide greater response at the beginning and end of the power band. This works well for on-road and racing applications for fast take-offs and high speed.