Carbman Replacement Carburetor for 21A707 21R707 21R777 21A907 21A977 Engines — Direct Fit with Gaskets

Carbman 590399 is a direct-fit replacement carburetor kit with gaskets designed to restore fuel delivery for lawn mowers using 21A707, 21R707, 21R777, 21A907 and 21A977 engines.

This Carbman replacement carburetor (parts 590399 / 796077) is built to match OEM specifications and includes mounting gaskets so you can swap it into compatible small engines without sourcing extra sealing parts. It’s intended for seasonal tune-ups or repairing carburetor-related running issues caused by wear, varnish build-up or failed diaphragms. The unit is sold as a part-for-part substitute and is easiest to install for those familiar with small-engine maintenance; professional installation is recommended for users who are not comfortable working with fuel systems.

How will this carburetor fit my engine model?

The Carbman 590399 replaces original carburetor part numbers 590399 and 796077 and is manufactured to fit a list of specific engine codes. Compatibility covers models stamped 21A707, 21R707, 21R777, 21A907 and 21A977. Before ordering, visually compare mounting points and throttle/choke linkages against your current carburetor to confirm an exact match.

• Direct replacement for part numbers: 590399 and 796077
• Designed for engines labeled: 21A707, 21R707, 21R777, 21A907, 21A977
• Includes mounting gaskets to simplify installation
• Check throttle/choke linkage orientation for final fit

What performance improvements should I expect after installing it?

Installing a fresh Carbman carburetor can return proper fuel/air metering, improving idle stability and throttle response if your old carb was clogged or worn. It won’t change engine power beyond restoring original performance, but it can reduce stalling, rough idling and hard starts caused by carburetor failure.

• Restores correct fuel delivery for smoother idle
• Reduces stalling and hesitation under load
• Improves cold-start reliability compared with degraded carburetors
• Maintains factory-level performance; not a performance upgrade

How difficult is installation and what do I need to know?

Installation is straightforward for anyone familiar with small-engine repairs: drain fuel, remove linkage and mounting bolts, swap the carburetor and attach the included gaskets. Carbman recommends professional installation if you lack experience—no instructions are supplied with the kit—so a technician can ensure correct adjustments and leak-free sealing.

• Turn off fuel and disconnect battery or spark plug before starting
• Remove old carburetor, replace mounting gasket with the included piece
• Reconnect throttle/choke linkages and fuel lines, then test for leaks
• Have a mechanic tune idle and mixture if necessary

What does the kit include and is support available?

The package contains the Carbman 590399 carburetor assembled for direct fitment plus the necessary mounting gaskets associated with part 796077. Carbman offers customer support for product questions and typically responds within 24 hours for fitment or after-sales inquiries.

• One Carbman 590399 carburetor unit
• Mounting gasket(s) matched to part 796077
• No printed installation manual included in the box
• Customer support available for compatibility or replacement questions

Who is this for: This Carbman carburetor kit is intended for homeowners, small-engine technicians and lawn-care professionals who need a straightforward, OEM-style replacement for the 590399/796077 carburetor family. It’s ideal when your mower exhibits fuel-delivery symptoms—such as rough idle, poor throttle response, or difficulty starting—or when a worn carburetor must be swapped out during routine service. Purchase this kit if you want a like-for-like replacement that includes gaskets, and arrange professional installation if you are unfamiliar with fuel-system work.