Satoh 650 accelerator pump modifications ???

Crazy Horse · Sep 9, 2015

Apparently, the accelerator pump that is in the carb kit for Satoh 650 carburetors does not fit ALL carburetors (some are Stromberg, some are Nikki's). Can anyone clarify what has to be done if the accelerator pump in the kit a person receives is not a perfect fit and something needs to be changed? I suspect that the modification has to do with the carb body itself (likely the top cover)I think and not to the pump parts that come in the kits.

Jim in Ma. · Sep 9, 2015

I got a rebuild kit for a Nikki carb for my S-650G. The accelerator pump did not fit The stem was to big. I was going to drill out the hole in the top of the carb but decided to try and take the pump apart. All I can say is "Don't Do IT".
I ended up sending the whole thing out to be rebuilt. Good luck

Crazy Horse · Sep 9, 2015

I've been told that some suppliers send an instruction sheet with the kit telling the buyer just what to do, sounds like drilling out the top plate is the fix but it would be nice to see something in writing so a guy doesn't screw anything up.

Crazy Horse · Sep 9, 2015

Where did you send the carb out to? Did they make the fix with the oversized stem on the accelerator pump? Did the end result work out for you and is the tractor running OK now? Some have said that the accelerator pump feature isn't even needed on a tractor, it's an automotive carb of course and who needs instant acceleration or power?

Jim in Ma. · Sep 9, 2015

I sent it to National carburetors in FL, they said they could rebuild it.
They were the best price I could find on line.
I have not got-en it back yet. They said expect a two week turn around.
I can only hope it turns out good.

jimg.allentown · Sep 10, 2015

The accelerator pump is not necessarily for "instant acceleration," but more for smooth increase in power output when the governor calls for it. As you load the engine, the governor operates the throttle to maintain RPMs. As the load increases, the governor opens the throttle to compensate. Without an accelerator pump, a sudden increase in loading will cause the engine to "bog" or hesitate when the throttle is increased. The accelerator pump reduces or eliminates that hesitation. Without it, the engine will hesitate or even stall out at times.

Crazy Horse · Sep 10, 2015

I'm not a mechanic but your advice makes sense and sounds correct to me, it is an automotive-type carburetor and those usually have accelerator pumps, it's obviously not designed to work without the feature even though it might work.

I talked to Bill at Valley Power (in Virginia I think) and he told me the "fix" is to drill out the top half of the carburetor (on those needing it) to 1/4" so the shaft of the accelerator pump in the kit will fit through the top of the carb if the opening is too small (the original pump shaft on some carbs is a smaller one). Obviously, care needed when doing this, use a drill press and keep the carb top level and secure, and use incremental drilling to 1/4" rather than trying to do it with a single 1/4" pass. Slow and easy wins the race I think.

Satoh 650 accelerator pump modifications ???

Crazy Horse

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Jim in Ma.

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Crazy Horse

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Crazy Horse

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Jim in Ma.

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jimg.allentown

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Crazy Horse

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