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Hi All.
This is my 1st post and this forum looks to be a great place to ask questions.
I have a John Deere LA130 riding mower that has been losing rpm or stalling when under load. It's also random. I'll be cutting grass and the engine will slowly lose rpm until I come to a stop and let the engine build up the rpm again over 15 seconds or so with the mower deck engaged. After the rpm's recover I'll proceed again but the same thing occurs again. Loss of engine rpm and the need to stop. If I disengage the mower deck the engine picks up rpm immediately. It only seems to lose rpm's when under load. If I don't stop and just keep cutting the grass it'll eventually just stall the motor but sometimes I can go a fair distance with no loss of rpm and no problems?
I did a full maintenance on it last month too to try and fix the problem but nothing worked. I put in new oil, oil filter, plugs, (gaped correctly too), checked for spark from both plugs and cables, (all good), and new gas filter and air filter.
This Briggs & Stratten motor ran perfectly last year and this problem just started the 1st month of summer after using it once for 2 hours with no issues.
Suggestions?

I have a john deere 155c and it is very similar to yours. I would first remove the deck and check all pulleys for free spin and play. Pay close attention to the spindles. Now would be a good time to grease them if they have grease zerks. While the deck is out, crawl under the mower and look at the drive belt pulleys. There are a couple of plastic pulleys that take the slack out of the belt when the brake/clutch is released that I believe may be your problem.

:welcome:

Welcome to the forum!

I'm going to move this thread over to our John Deere section.

Your tension spring on the mower deck blades is broken.

Check the belt & spindles for free movement as previously advised.
If everything turns freely then start the engine, set the parking brake and set the throttle to slow.
Get off and go around to the carb.
put you finger on the governor arm and work the throttle from there.
Accelerate the engine by pushing on the governor arm ( you can use the butterfly on the carb but the governor arm is easier to get at.)

The engine should run smoothly from idle to wide open throttle.
DO not hold the throttle wide open as the engine will over rev
It is just a smooth push all the way to fully open and back again to idle

If the engine faulters, let us know what it does, misses, blows black smoke , runs a little then misses then runs.

Hi Lawn King.
I did push on the governor arm and the motor revs up nicely. Releasing the arm the motor will back down nice and smooth. No hesitation or back firing at all. Both governor springs are intact and attached to the arm points where they should be. The motor has always run great. It's just when the PTO is engaged that the RPM drops while under load from the blades? Disengaging the PTO causes the motor RPM's to recover quickly with no problems. I can drive it at full or half throttle without losing power.

BCJS said:

Hi Lawn King.
I did push on the governor arm and the motor revs up nicely. Releasing the arm the motor will back down nice and smooth. No hesitation or back firing at all. Both governor springs are intact and attached to the arm points where they should be. The motor has always run great. It's just when the PTO is engaged that the RPM drops while under load from the blades? Disengaging the PTO causes the motor RPM's to recover quickly with no problems. I can drive it at full or half throttle without losing power.

Click to expand...

Do what dfbroxy says in second post.

BCJS said:

Hi Lawn King.
I did push on the governor arm and the motor revs up nicely. Releasing the arm the motor will back down nice and smooth. No hesitation or back firing at all. Both governor springs are intact and attached to the arm points where they should be. The motor has always run great. It's just when the PTO is engaged that the RPM drops while under load from the blades? Disengaging the PTO causes the motor RPM's to recover quickly with no problems. I can drive it at full or half throttle without losing power.

Click to expand...

Thank you.
We needed to know if it was an engine problem or a mower problem.
IF the engine will run right up to wide open ( sounds like it will blow up ) then back to low idle cleanly then we now know the problem is in the deck thus cutting the list of probable causes in half.

So from here we start with the basics like checking the blades are on the right way round.
Then checking for debris wrapped around the spindles
After that there is the blade brake no fully releasing
Pulleys with frozen bearings
Blade spindle bearing frozen
Belt to tight

It will be one of the above.
Remove the deck and the belt.
spin everything.
All parts should spin freely and quietly

Check all of the above first, then with belt removed start engine and engage pto to see if the engine loosed rpms that way. If it does it will be a bad electric clutch(pto). The clutch has sealed bearings that can go bad too.

dfbroxy said:

Check all of the above first, then with belt removed start engine and engage pto to see if the engine loosed rpms that way. If it does it will be a bad electric clutch(pto). The clutch has sealed bearings that can go bad too.

Click to expand...

Thanks, forgot this has an electric clutch so it could be a parrasitic electrical load as well.

Problem Solved
I ended up taking my JD to the local dealer for service as nothing was working.
Turned out that 1 of the push rods on my 2 cylinder engine had slipped off the rocker arm. This isn't a common problem but it accounts for the lack of power. This effectively cut the power output to half of what it should be. This was why my mower was stalling.
The giveaway in diagnosing this problem is the spark plugs. Removing the spark plugs will indicate if the cylinder is firing or not. If the cylinder is firing the spark plug will be dry. The non firing cylinder shows the spark plug is "wet". It's wet because there's no combustion taking place with the push rod dislocated from the rocker arm.
Simple fix and she's running a full power again