Torn intake boot / air leak

The is a round-slide, constant velocity (CV) carburetor commonly found on mid-sized 150cc 4-stroke engines, such as those in GY6-equipped vehicles and Yerf-Dog utility carts.

If you’ve been wrenching on a scooter, dirt bike, or a small ATV (like the Yamaha Vino 125 or early Suzuki Burgman), you’ve likely met the Mikuni BS25. It’s a reliable, constant-depression (CV) carburetor, but it has a dirty little secret: