The Zenith Model 87 was a single barrel sidedraft (horizontal) carburetor manufactured from the 1940s until 2025. It was built in Zenith size 5 (throttle bore 5/8" nominal), size 6 (throttle bore 3/4" nominal) and size 8 (throttle bore 1" nominal). It was used on a variety of industrial applications, including many Wisconsin engines.
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How to find Zenith carburetor numbers