Inside you will find the factory breakout diagram of the Satoh Bison Nikki carburetor. Note that two similar but different types of carburetors were used on the S650G over the years (Stromberg and Nikki). Valley Power has a simple illustration to help you identify which is installed on your tractor.

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To Rebuild or Not, that is the question.

If you are having trouble with clogged jets or a gummed up carburetor you may or may not need to disassemble and rebuild your carb for best performance. Unfortunately, the gasoline of today contains ethanol which is terrible for motors that do not see daily use. The ethanol in the fuel breaks down and turns to gum and varnish quickly, even when you use fuel stabilizers such as Sea Foam or even Stabil. To prevent this in any carbureted engine you can drain the fuel from the float bowl after every use.

Before you decide to rebuild your carb you may be able to clear clogged jets without disassembling the carburetor thanks to the design of the Nikki carb. If your Satoh S650G Bison will not run without the choke partially on when warm chances are you have clogged jets. Depending on how bad your clog is you may be able to fix the issue with spray carb cleaner following these steps:

1. Remove the rubber air hose from the carb.
2. Drain your float bowl by unscrewing and removing the drain screw which will give you access to the main jet under the carb bowl.
3. Spray carb cleaner using the straw into the drain hole through the main jet a few times. Once the main jet is clear you should see carb cleaner drip out of the main nozzle from the top of the carb.
4. Re-insert and re-tighten the drain screw.
5. Spray carb cleaner down the “Air Bent Pipe” from the top of the carb mouth, this will fill the fuel bowl with carb cleaner.
6. Let the carb cleaner sit for at least 30 minutes in the carb bowl before trying to start the tractor.
7. With the choke on to create a stronger vacuum, crank the tractor a couple of times to suck the carb cleaner to the slow jet and through the fuel delivery ports.
8. Let the carb cleaner sit for another half hour, then start the tractor using the choke to pull fuel to the carb. Once started, immediately begin to push the choke in / turn it off slowly to see if your tractor is now running smoothly and properly without the use of the choke.

If your tractor still does not run properly but does have noticeable improvement, try the steps above again but wait longer with the carb cleaner in the carb. Otherwise removal of the carburetor and a thorough cleaning is necessary. The good news is the rebuild kits are easy to find from the links on this site, Amazon, and even Ebay.

If your carburetor is missing or broken some have reported that a replacement carburetor for a YALE Forklift part number: GP-050-RA should fit. We can not confirm this is a direct replacement but reviewing pictures of this carburetor it looks pretty much identical to the Nikki carb used on the Satoh s650g.

An alternative carb replacement option can be found on our Alternative Carburetor page.