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Lawn-Boy fan
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Discussion Starter · #1 ·
My main mower is a 3 speed, F powered, Lawnboy. Shortly after I bought it, I replaced the factory blade with a Gator blade. I sharpened it almost to a knife sharpness using a ******* file. I've never been very impressed with the cut. I cut my grass at 3" and there always would be stray grass blades that would be longer than the cut grass that the mower wouldn't cut.

Well, today, just for the heck of it, I lowered the engine's RPMs. It seems to cut much better now and hardly left any long blades of grass at all.

My thinking it that at the higher RPMs, the gator blade blows the grass down due to the "fan affect," causing some grass to not be cut. At the lower RPMs, maybe it does this less?

Either way, it's easier on the engine, and I'm happier.
 

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5K Poster!!!!
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I have the same problem when I mow my front yard, which is all St. Augustine, so what I do if I really want a clean cut is mow again 90 degrees from the first mowing.
 

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I've also noticed that with my C21CPN. I cut at the slowest speed, but I also walk a little slower. Cutting height is about 2 3/4" and the lawn looks great. I use a mulch plug and fan in addition to the std factory blade. Much better then the (trash rescue, but mint condition) 6 3/4hp Craftsman I was using before I found this LB. The Cr****n was leaving way too many uncut blades of grass.

I was out of town this past weekend and my son used the Cr****n again, and you can tell the difference in the cut right away! I'd swear the grass almost has a glow to it after being cut with the LB.

Cheers Lawnboy!
 

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I have noticed uncut blades and thought faster would be better. This is especially when the grass is a little longer. When bagging, there is no problem. I do notice that the steel deck has less issue that I think may be due to the shap of the deck and it is a little deeper. The 10550 leaves some behind but never bogs down. I gave it a few clicks on the governor and it didn't get better. Maybe I will slow it down some and see what happens. I do walk slower with the engine speed down so that will help too. I think the sp with the bail lever is better that the easy-stride or whatever they call it.

GP
 

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Lifetime Lawn Guy
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Air turbulance. If I spelled that right... It's just a matter of the blade moving more air than the deck can handle at once. If the grass is thick it's a good thing, but when the grass is thinner and at higher cutting heights it has a counter effect. Excess "wind" can't exit the chute so it ends up going where ever, blowing the grass with it. Using a mulch plug obviously there's no where for the air to go other than down to start with, so there too slowing the engine = less air moved = less grass being pushed down and away from the blade. However as soon as you encounter thick grass again throttle back up!

I do lawn care for a living, but run everything at WOT all the time. Air cooled engines are designed to run at max throttle to properly cool themselves. Just something to think about.
 

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"I . . . . . run everything at WOT all the time. Air cooled engines are designed to run at max throttle to properly cool themselves. Just something to think about."

Sorry to be so blunt, but that's just dead wrong. So long as heat development and heat rejection flow rates don't cause any part temperatures to rise beyond their working limits, there is NO need to run air cooled engines at Wide Open Throttle. When engines are driving especially heavy loads, low speed operation can fail to drive enough air through heat-rejection surfaces to prevent overheating. But that is not a typical mowing circumstance. Most air cooled mower engine overheating is caused by physical obstructions limiting or even preventing air flow over specific surfaces. Blow out your grass debris frequently. It is perfectly safe to run well-maintained air cooled at lower speeds driving typical mowing loads. All other factors remaining constant, expected service life between rebuilds will be longer if they are operated at lower speeds than at WOT.

I've been involved with engine design and development for more years than some of this forum's participants have been alive.
John
 

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News to me... I believe that every engine owners manual I've read always says to operate the engine at full throttle so that it will cool itself properly, I've been told the same thing over the years as well. Not arguing with you or telling you are wrong, just pointing out that my sources have always pointed me to running them WOT.
 

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Lawn-Boy fan
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Discussion Starter · #8 · (Edited)
I do know that with transportation devices that have air-cooled engines, it is air movement that cools the engine, not necessarily the RPM of the engine. Maybe that's why you could be thinking that running at WOT is best for cooling. For example, for years, Harleys had problems with overheating when idling in traffic, but when you run them at higher speeds (on the highway), the engine is also at a higher RPM, but the actual cooling is from air movement over the cooling fins.

Also, with electric motors, they are designed to run at higher speeds to cool themselves because the spinning of the motor helps to "blow" the heat out of the motor. Gas engines don't cool themselves this way, although, I could be wrong.

The more I think about it.....at higher RPMs, more fresh air is "pumped" through the engine. Perhaps that is part of the cooling effect, but I would think that the more you rev an engine, the hotter it gets whether it is air or water cooled.

By the way, I didn't mention it in my original post, but I have the mulch guard installed and I mow in opposite directions each time I mow and it was still leaving blades behind before at higher RPMs. Maybe the exhaust blowing is knocking down the blades of grass at higher RPMs?

Whenever I use my old 1980's mowers, they seem to run at a much lower RPM as they just humm along and they do a great job at mowing. Maybe Lawn-Boy increased the horsepower on newer F engines by bumping the RPMs.
 

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Engines need to run at full throttle not so much for cooling but because most lawn mowers are badly underpowered.
 

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OMC & Ariens lover!
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i always run all my mowers at low speed when mowing,but if they have the throttle on the upper handle ill use WOT.seems to me having the engine running at a slower speed takes less fuel and most of the time i dont need normal or fast.i usually put up a fight to put it on fast/normal.
 

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News to me... I believe that every engine owners manual I've read always says to operate the engine at full throttle so that it will cool itself properly, I've been told the same thing over the years as well. Not arguing with you or telling you are wrong, just pointing out that my sources have always pointed me to running them WOT.
This is the same information I have read in all my manuals be it Gravely , Craftsman,John Deere, Ariens and Snapper to name a few .
The manual I m looking at right now for Ariens 936 series states " mowing at a lower throttle setting causes blade to tear grass,resulting in poor lawn appearance" , "That attachments should be operated at full throttle unless otherwise specified in attachments owners manual".

The John Deere 140 manual states " Raise throttle lever to operate attachments at full engine speed"

If you go to the other extreme the John Deere manual for the 140 states "do not operate engine at idle speed for a prolonged period of time because engine will overheat, causing internal damage".

All I m saying is that other manufactures may not all say the same thing as times change and its best to read and know all about your individual equipment operating instructions before you do something that does more harm than good .

As others have said its good practice to check the oil level before you operate an engine and change its oil according to the mfgs instructions .
 
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