Best mowing RPM for Kohler 25hp Courage

[gfp55]

3600 RPM max

 

[fox5flyer]

3600 RPM max

OK, we have 3200, 3600, 3800. (drum roll please)

MODEL Courage SV730
MAX. POWER @ 3600 RPM hp (kW) 25 (18.6)
DISPLACEMENT cu. in. (cc) 44 (725)
BORE in. (mm) 3.3 (83)
STROKE in. (mm) 2.6 (67)
PEAK TORQUE @ MAXIMUM lbs. ft. (Nm) 44.8 (60.7) @ 2200
COMPRESSION RATIO 9:1
DRY WEIGHT lbs. (kg) 91 (41.5)
OIL CAPACITY U.S. quarts (liters) 2.0 (1.9)
LUBRICATION Pressure w/full-flow filter
DIMENSIONS L x W x H in. 18.5 x 17.8 x 13.4

There is also an excellent youtube tutorial on adjusting the governor.
Small Engine Repair: How to Adjust the Mechanical Governor on a Kohler V-Twin Engine - YouTube

Thanks for everyone's responses. I learned something new today and now my headache is suddenly gone!
Deke
NE Michigan

 

[fox5flyer]

My new tach arrived and after about a 15 minute install, configuration, and startup, it maxed at 3260rpm with full power and mower deck running. Quite a bit short of the 3600 I was expecting. Looks like an adjustment of the governor is in order. Does anyone have any input before I tackle this? I just want it right.
Deke
NE Michigan

 

[SeniorCitizen]

Hi. I'm a newbie from NE Michigan.
I have a Husqvarna MZ5225 ZT mower and am planning to install a tach. Reason is, I need to figure out the optimum RPM for best tip speed of the blades. I'm not a commercial mower, but I have a lot to mow and I've learned that keeping the blades sharp and RPMs up will give the best performance and efficiency. I use full synthetic oil.
Once I install the tach, can anyone tell me what RPM I should be running with a formula to determine my blade tip speeds so that I'm not just guessing?
There must be one of you techies out there who would like to tackle this one.
Thanks in advance
Deke

The formula for calculating rpm of the final sheave is RPM of the engine times the diameter of all of the drive sheaves divided by all the driven sheaves.

Example: My mower is a 42" cut so the blades are approximately 21" long.
If the engine is at 3,600 RPM and the engine pulley is 4" in diameter with the blade pulleys being 5" dia. I would multiply 3,600 x 4 ( engine pulley dia. ) and divide by 5 ( blade pulley dia. ). This would give my blades 2,880 RPM.

To find blade tip speed in feet / minute I would multiply 21" circle dia. x 3.14 to get the circumference of the circle in inches, then divide that by 12 to get circumference in feet which would be 5.495 ft. Now that we have the circumference in ft. we can take that x the driven pulley RPM and we have tip speed in ft. / minute which would be 15,825. This calculation is not including belt slippage which is around 3 percent on a V belt. ( Moot Point )

If your tractor has a jack shaft the same formula applies. Engine rpm X all the drive sheaves divided by all the driven sheaves to get final sheave RPM.

 

[fox5flyer]

The formula for calculating rpm of the final sheave is RPM of the engine times the diameter of all of the drive sheaves divided all the driven sheaves.

Example: My mower is a 42" cut so the blades are approximately 21" long.
If the engine is at 3,600 RPM and the engine pulley is 4" in diameter with the blade pulleys being 5" dia. I would multiply 3,600 x 4 ( engine pulley dia. ) and divide by 5 ( blade pulley dia. ). This would give my blades 2,880 RPM.

To find blade tip speed in feet / minute I would multiply 21" circle dia. x 3.14 to get the circumference of the circle in inches, then divide that by 12 to get circumference in feet which would be 5.495 ft. Now that we have the circumference in ft. we can take that x the driven pulley RPM and we have tip speed in ft. / minute which would be 15,825. This calculation is not including belt slippage which is around 3 percent on a V belt. ( Moot Point )

If your tractor has a jack shaft the same formula applies. Engine rpm X all the drive sheaves divided by all the driven sheaves to get final sheave RPM.

Thank you. That is the formula that I was looking for and I've printed it out for later this evening. I was told by a (very) knowledgeable person that the tip speed should be somewhere near, but below, the speed of sound, generally around 18,000 fps. He told me that if the blades were not starting to howl that the tip speed was not fast enough for efficient and clean cutting. Some of you may laugh at this, as it sounds a bit anal, but I'm just the messenger and I don't know either way. Right now, though, I believe I need to get my engine rpm higher as it is running about 300rpm too low. Then again, am I really going to realize any noticeable difference? I guess I'll find out.

 

[fox5flyer]

Thank you. That is the formula that I was looking for and I've printed it out for later this evening. I was told by a (very) knowledgeable person that the tip speed should be somewhere near, but below, the speed of sound, generally around 18,000 fps. He told me that if the blades were not starting to howl that the tip speed was not fast enough for efficient and clean cutting. Some of you may laugh at this, as it sounds a bit anal, but I'm just the messenger and I don't know either way. Right now, though, I believe I need to get my engine rpm higher as it is running about 300rpm too low. Then again, am I really going to realize any noticeable difference? I guess I'll find out.

I just calculated that with my current rpm of 3260 and pullies (drive/6", driven/5") sizes with 18" blades, my tip speed is 15,354.
Est using 3600 rpm my tip speed would be 20,347.
I haven't adjusted anything yet and before I do anything, does anyone else have any input, other than to ask if I have too much time on my hands? Actually, I'm a pretty busy guy. I just want this mower to work to it's max potential as I have a lot of personal lawn and an airstrip to mow.
Thanks folks.
I love these forums.
Deke
NE Michigan

 

[SeniorCitizen]

I just calculated that with my current rpm of 3260 and pullies (drive/6", driven/5") sizes with 18" blades, my tip speed is 15,354.
Est using 3600 rpm my tip speed would be 20,347.
I haven't adjusted anything yet and before I do anything, does anyone else have any input, other than to ask if I have too much time on my hands? Actually, I'm a pretty busy guy. I just want this mower to work to it's max potential as I have a lot of personal lawn and an airstrip to mow.
Thanks folks.
I love these forums.
Deke
NE Michigan

If mine is running as designed I don't worry about the speed much but keeping the blades sharp, belt tension correct and the under side of the deck clean is important to me.

 

[gfp55]

My new tach arrived and after about a 15 minute install, configuration, and startup, it maxed at 3260rpm with full power and mower deck running. Quite a bit short of the 3600 I was expecting. Looks like an adjustment of the governor is in order. Does anyone have any input before I tackle this? I just want it right.
Deke
NE Michigan

Your engine has a max RPM of 3600 with no load. Wide Open Throttle without any load, no deck load, engine only. You posted "3260rpm with full power and mower deck running." What's the RPM without load. What kind of tachometer do you have? You should use a laser tachometer to check your tachs accuracy, then you know your RPM numbers are correct. Just saying....

 

[Fish]

The engine mfg. makes their rpms variable, so that the different companies can set their own speeds, it is all about the blade tip speeds and the lawyers!!!!

 

[gfp55]

The engine mfg. makes their rpms variable, so that the different companies can set their own speeds, it is all about the blade tip speeds and the lawyers!!!!

True....