Kawasaki FS481V Throttle Stop... Possible free conversion to FS600V?

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Old 01-20-19, 05:34 AM
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Kawasaki FS481V Throttle Stop... Possible free conversion to FS600V?

I have an Exmark M16KA362 w/ a Kawasaki FS481V-AS05. I took the carb off the other day to clean it and noticed that there is a small throttle stop on the side that prevents the butterfly from opening all the way.

I recall reading that the only difference between the FS481V the more powerful versions of the same 603cc displacement is the carb. That got me wondering... could grinding off this tiny throttle stop turn the FS481V into say, an FS600V? Not that it needs any more power, but the carb is off anyway...

See attached pics that show:
1. The butterfly position at wide-open-throttle
2. The throttle stop that is being hit that could easily be ground off

Think there is any harm in trying this? The carb is very expensive so if there's any chance that this will mess something up I won't try it.

Thanks,

- Joe
 
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Old 01-20-19, 12:06 PM
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It amounts to doing the same thing as a restrictor plate in a carb stock car. Those were done to cap the performance. What you have may be done for the application or for the engineering of the engine. Its hard to tell if you open that throttle up the engine would fly apart. There's usually governors on them to handle that function.

Seems a little odd but a good rule of thumb is: if it's working well like it is, don't mess with it. The two carbs may have some other differences, like jetting and air flow passages. Also each may be specific to horsepower and torque curves relative to throttle opening.
 
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Old 01-20-19, 01:49 PM
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Are you coming up short for power currently? The governor will restrict the throttle to limit the maximum rpm. You will only have a fully open butterfly when the engine is under heavy load requiring all it's power.


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Me, I'd bend the throttle stop up (so it can be bent back down if needed) and give it a try. After bending the tab up make sure the throttle cable can pull the extra distance to fully open the throttle.
 
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Old 01-20-19, 02:51 PM
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It's limiting your power. It won't make any difference in most conditions unless you are often working the mower to it's full potential. If you are pulling hard to cut thick grass and on the verge of bogging out the engine, then it could help to grind it. I doubt it will hurt a thing if you do it. You would also need to re-set the governor so that it can allow movement past that spot or it won't ever go to full throttle anyway because that's where the governor is set to realize full travel.
 
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Old 01-20-19, 05:38 PM
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Thanks everyone! This engine is plenty powerful .. esp with only a 36" deck. If I ever encounter a situation where I need more power I'll try bending the tab on the throttle as suggested.

I just compared carb part numbers between the FS481V and the FS600V and the only part number differences I could see were the main nozzle. Both use a #102 jet. I didn't see a separate part number for the carb casting - that might only be available as part of the complete assembly, which retails for $225.

Resetting the governor on this engine looks really easy. Almost all types of maintenance and adjustments on this engine are super easy. Kudos to Kawasaki for a good design. I've heard some of these engine are blowing up after the 1,000 hr mark... hope mine holds together. I bought it used with an unknown number of hours. The prev. owner estimated 500 hrs, but he also told me it was 5 years old and it turns out it is 8 years old. I had a coil go bad on it after I bought it and I didn't even notice a difference in power... just smelled the raw gas
 

Last edited by joec2000; 01-20-19 at 06:16 PM.
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