Lawn Mower Cutting Poorly, Possible Power Loss

[derekwnickerson]

I have an old John Deere 111, circa 1980, that seems to lose power when the blades are under an insignificant load. I'm not cutting very tall or abnormally heavy grass -- just your run of the mill yard here. The blades have been sharpened on a bench grinder and tested for balance. I've test the deck pulleys and they swing freely. Oil changed. Cleaned out the carb and replaced the fuel filter as well.

When I engage the blades and without lowering the deck, they run at full power -- though it does leave an uneven, choppy cut on the grass. Now, when I lower the blades less than an inch, I can sense the blades not rotating at full power. The quality of the cut looks about like that of a mower being overloaded and choked out, but the engine runs fine the entire time. The quality improves when I reduce the speed to a snails crawl (2 of 5), but it is by no means perfect.

Does anyone have some advice on to why my mower is cutting poorly and also losing power when I lower the deck? I know this is a smaller JD, but this is ridiculous. Thanks for your help.

 

[bertsmobile1]

:welcome:

Congratulations,
36 years and still mowing .
Might slow done some of the prejudiced critics here who detest JD get their jollies by telling every one never to touch a JD .
Anyway I am a bit confussed by your descriptions.
In one line you say it looses power and in the next you say the engine is running fine.

If you are still running the original pulleys they will be worn out by now.
The rubber belt is softer than the steel pulleys but over time the steel wears, the gap widens and the belts can not grip as tight as they should.
I service a lot of very old mowers and it is standard practice to fit a shorter belt.
This is a temporary fix ( 5 years a best ) as eventually the pulley will wear so much that the belt is touching the bottom of the V where it can not grip at all.
However with a lot of older mowers another 3 to 5 is all the rest of the machine will be good for in any case.

Just returned a 155 , owner is over the moon . Bitched about the $ 600 for new pulleys all round ( including tranny ) but was last seen powering down his lawn with a smile from ear to ear.

 

[Rivets]

When was the last time the belt was replaced?

 

[reynoldston]

As I recall that has a 11 HP Briggs. You say you are cutting tall grass down to less then 1 inch. Maybe the you might have better luck if you made several passes seeing its only a 11 HP engine. That mower also has a double pulley on the back side of the deck that can have some bearing or tension spring problem's you can check. That tension spring is also adjustable. Still check the belt as said earlier.

 

[Carscw]

:welcome: Congratulations, 36 years and still mowing . Might slow done some of the prejudiced critics here who detest JD get their jollies by telling every one never to touch a JD . Anyway I am a bit confussed by your descriptions. In one line you say it looses power and in the next you say the engine is running fine. If you are still running the original pulleys they will be worn out by now. The rubber belt is softer than the steel pulleys but over time the steel wears, the gap widens and the belts can not grip as tight as they should. I service a lot of very old mowers and it is standard practice to fit a shorter belt. This is a temporary fix ( 5 years a best ) as eventually the pulley will wear so much that the belt is touching the bottom of the V where it can not grip at all. However with a lot of older mowers another 3 to 5 is all the rest of the machine will be good for in any case. Just returned a 155 , owner is over the moon . Bitched about the $ 600 for new pulleys all round ( including tranny ) but was last seen powering down his lawn with a smile from ear to ear.

Not liking JD has nothing to do with getting your jollies off. In 1980 I would have got a JD
In 2016 they are bottom of the chum barrel
Even their industrial equipment is not up to par. They went to building cheap equipment hoping their good name would carry them.

Sounds to me like the belt is slipping.
I agree try a shorter belt. And check the idler pulley spring.
JD sells good belts. I use them on my Toro's. Half the price of toro belts and last longer.

 

[derekwnickerson]

Thank you for all the feedback guys. I checked the tension in the belts and sure enough they were not tight. The idler pulley is in great condition, but the bracket the pulleys are mounted on does not want to pivot freely (marked with black box in image). I tried knocking it loose after using PB blaster, but it only moves if I smack it with a mallet. Until I'm able to free it up, I won't know whether its the spring or belt that needs replaced, probably both.

Right now, it has a 60-inch deck drive belt, but should I get a shorter belt?

 

[reynoldston]

Thank you for all the feedback guys. I checked the tension in the belts and sure enough they were not tight. The idler pulley is in great condition, but the bracket the pulleys are mounted on does not want to pivot freely (marked with black box in image). I tried knocking it loose after using PB blaster, but it only moves if I smack it with a mallet. Until I'm able to free it up, I won't know whether its the spring or belt that needs replaced, probably both.

Right now, it has a 60-inch deck drive belt, but should I get a shorter belt?

View attachment 29656

It is the later 100 series that has the adjustable spring tensioner yours being earlier it doesn't. You will have to take the belt tensioner apart and free it up. Not that bad of a job seeing you have the deck off. Get the right belt (OEM) from John Deere or you will have more problems down the road.