RPMs: To Adjust or Not to Adjust, That is the question

RhettWS

RhettWS

Well-Known Member
Good afternoon,

I just purchased and used a new laser tachometer to check my engine rpms. I have a Raptor SD, 54" deck, with a Kaw FR691V. The specks indicate the high idle speed should be 3600 +/- 50 rpms.

With no blades engaged I got values right at 3600. With the blades engaged it dropped down to 3462 rpm.

Does it need tweaking or not? I assume high idle does not mean with the blades engaged.

Thanks .......... Rhett
 
Well now, me being me I would be setting the speed to an even 3500 rpm with the blades engaged and gain the 200fpm blade speed.. But thats just me :)
 
I'm not tempted to fool with it myself. If needed I would bring it to the dealer. Wish I could get it to turn 3600 with the blades engaged. At some point, when I have nothing to do I will calculate blade tip speed. I think it was advertised at about 18,900 fpm if I remember correctly.
 
Curiously, why wouldn't the governor adjust the rpms closer to 3600 than what I found with the blades engaged?

Seems like a pretty substantial drop for just having the blades engaged without cutting any grass. To reiterate, the mower was sitting still and not cutting grass. Had my wife sit on the mower while I had the blades engaged.

Thanks again
 
RhettWS said:
Curiously, why wouldn't the governor adjust the rpms closer to 3600 than what I found with the blades engaged?

Seems like a pretty substantial drop for just having the blades engaged without cutting any grass. To reiterate, the mower was sitting still and not cutting grass. Had my wife sit on the mower while I had the blades engaged.

Thanks again
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Some drop is to be expected.. But, as I said, I would be sorely tempted to up the RPMs. But then me a Toolman Taylor have a lot in common ;) Simple governor adjustment would be all it would take.
 
Hopefully I'll get a few other opinions. I'm no mechanic by any means but it seems to me it shouldn't drop that much. I wonder if they check high idle on a push mower with the blade on the unit or off?

Just wondering out loud. Thanks
 
RhettWS said:
Hopefully I'll get a few other opinions. I'm no mechanic by any means but it seems to me it shouldn't drop that much. I wonder if they check high idle on a push mower with the blade on the unit or off?

Just wondering out loud. Thanks
Click to expand...

See what the claimed blade RPM is suppose to be and adjust to that.. Speaking of which, did you put aftermarket blades on? Could be high-lift blades slowing it down.
 
You may be able to increase the governor sensitivity so it will maintain engine RPM closer to 3,600 with the blades engaged and the machine moving.
Always mark or make note of where the governor spring was originally setup so you can go back to that setting if need be.
Many new machines are setup to run between 3,200 and 3,400 RPM. This was done in an attempt to increase engine life.
 
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Me thinks more like to get under emission regulations which if the USA is the same as here ( usually is cause we just copy you lot ) the specification stipulates max pollutants at operation speeds, thus lower speed = less ppm .
 
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