How does CCs affect blade power and torque?

TobyU

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I tried that. I only have the bag for the mower (just found it as I was cleaning out the garage the other day)

I tried to open the side discharge. I don't have a chute, so it just clogged immediately (I had a stick to hold it open). Same with the rear discharge, except it only clogged if I didn't set it to fully open. It worked better, but it still bogged down bad.

For all the people saying to set it to the highest setting: Duh. That was the first thing I did. 4" isn't really gonna make a difference to 18-24" grass cutting LOL. Even Hondas only go to 5 or 6"...
You should never really open one with the back open and even if you prop it up in just a little bit it still gets grass out of your feet and stuff is annoying. The stick method for the side works but typically not as well as the actual discharge flat. It should be able to order one online. They work quite nicely.
 

TobyU

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Thanks for the question. I got my numbers from an online calculator. I'll admit I was a very skeptical. I did more research and found a number of sites that showed the divisor could be anywhere between 25 and 40. This makes a lot more sense to me. In the future, I'm going to stick with 40 and even that seems a little low
Classic example of why you shouldn't believe everything you find from google, we Wikipedia or online. Lol

I have literally worked on thousands of these mowers and I know plenty of people today are skeptical and don't like to believe anything a person says but I only speak in actual facts from experience.
If I don't know, I clearly tell somebody I really don't know but this is what I would try etc.
 

georgPru2

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I want to get a mower engine and swap onto my little 21" 140cc Craftsman. I let my yard get way too high and went to mow it, but it was barely able to handle it, and I had to push it 2ft, backtrack 3, then go forward slowly.

Anyway, I was looking at a new mower, but they're all 150 or 170 or 163 cc (for the well rated ones. There's several 200ish cc ones for outrageous money, or with like 2 stars.

So, I'm curious. How much does engine CC actually do? Will I notice a difference between my 140cc and a 150? What about 163 or 170? Where would I need to go to buy a bigger engine that I could just swap onto the mower?
CC refers to engine size, not horsepower. Before B&S went and started measuring horsepower differently, all U.S. made equipment was measured in cu inches. If you are mulching/bagging too tall grass, NO LAWN MOWER [save a 2 cycle Lawnboy] will cut that mess. Just get cut short, and use your old machine. CC=cubic centimeter, and cu inch= cubic inches.
 

Gym123

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I'm late to this discussion but wanted to add my 2-cents about replacement engines. About 30 years ago I had a small engine repair shop. I found that the vertical shaft B&S engines that Craftsman placed on their push mower decks were unique due to PTO shaft length and blade mounting. They forced most customers to have to get their replacement engine from Sears/Craftsman. Briggs & Stratton would not sell the engine to even repair shops. So if you are planning to replace your engine on a Craftsman deck be mindfully of that.
The B&S parts store shows several engines for sale and in stock- the 17.5HP was about $750, IIRC.
 

Gym123

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CC refers to engine size, not horsepower. Before B&S went and started measuring horsepower differently, all U.S. made equipment was measured in cu inches. If you are mulching/bagging too tall grass, NO LAWN MOWER [save a 2 cycle Lawnboy] will cut that mess. Just get cut short, and use your old machine. CC=cubic centimeter, and cu inch= cubic inches.
How do they measure HP now and why does the change from cu inches to Metric matter? HP is a calculated value, just like Newton-Meters or Joules.
 

Gord Baker

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How do they measure HP now and why does the change from cu inches to Metric matter? HP is a calculated value, just like Newton-Meters or Joules.
The Change to metric from Normal is thanks to the LIEberals in Canada. Rated HP became a huge problem when JD was caught exaggerating the true HP. They paid Dearly for this. Now Small engines are measured in Torque Ft or in. pounds which few understand.
HP is how fast you hit the wall, Torque is how far you move the wall! You're welcome.
 

Honest Abe

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sounds like you need a goat instead of a mower...
 

7394

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Rated HP became a huge problem when JD was caught exaggerating the true HP. They paid Dearly for this.
This happened to Briggs too. Long ago..
 

Gym123

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T

The Change to metric from Normal is thanks to the LIEberals in Canada. Rated HP became a huge problem when JD was caught exaggerating the true HP. They paid Dearly for this. Now Small engines are measured in Torque Ft or in. pounds which few understand.
HP is how fast you hit the wall, Torque is how far you move the wall! You're welcome.
The manufacturers could have been made to show HP and Torque in the way many other engines are rated, but it would confuse the people who don't care about or understand car performance- show a Power and Torque curve and where it was connected to the measurement device- crank or at some point after, like the PTO shaft. Done. No need to change to Metric by Canada, but this kind of shows that their legislators don't quite understand how this could have been solved.

If a manufacturer wants to lie, let them suffer the consequences from being discovered.

I worked for boat dealers and some engine manufacturers showed the power and torque measured at the crank while others showed it at the prop. We had discussions (our side) and arguments (the other side) at boat shows where they went on about the power of their boats being measured at the prop, while ours were measured at the crank- at one point, I said "But torque is what turns the prop shaft" and they left us alone.

I heard a definition of Torque when I was in college at an engineering school that involved pushing something down while standing at a toilet first thing in the morning, resulting in the person being flipped over.......it wasn't the flush handle on the toilet.
 

Gym123

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To the OP-

The saying in drag racing "There's no replacement for displacement' is still valid for these, but we're working with much smaller engines and in order to really see the effect of a larger engine for this purpose, we need to look at the whole machine. As an example, the 17.5HP Briggs engine is .5 Liter. That's not much but there are ways to produce more torque- longer stroke, created by the crankshaft and using a smaller diameter piston for the same displacement. The crank is rotated by combustion in a larger circle, so we need to look at it as if someone had put a pipe on a wrench in order to increase torque- it's harder to rotate the crank with a shorter lever arm (smaller diameter of rotation).

Then, we need to look at the effect of the grass resisting the blade's rotation and this is why a sharp blade and correct mower speed are important- the blade is only sharpened close to the end and moving too fast causes the grass to pass the sharp edge, which just grabs and causes the engine to bog.

If you slow down, it will cut better. Extremely tall grass will require more than one pass with the deck set higher for the first.
 
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