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Deere 100 Series Questions

11K views 56 replies 4 participants last post by  FPMotorsports 
#1 ·
Afternoon folks, hows everyone been running?

Recently just came across a john deere las100 with about 600 hours on it. It starts fine, runs great for about 15-20 minutes than seems to lose power. It doesnt surge, and it apparently only started happening after a few cuts in the spring.

Any ideas of what this issue may be?! I have yet to do ANYTHING to it, i will start in the morning (to damn hot right now 36 celcius)

What troubleshooting steps would you take?

Any and all recommendations are greatly appreciated!
 
#2 · (Edited)
May be getting hot. Use an air compressor to blow any debris out from under the cooling fan. Also, buy yourself a new gas cap as the tiny hole usually gets plugged up after a couple seasons of use. Install a new air filter and fuel filter. Some Seafoam in the tank might not be a bad idea either. Finally, adjust the valves, which is pretty easy to do. If it still loses power, check the compression. Remember that properly-adjusted belts, a sharp blade and clean deck will lower stress on an engine too.

 
#3 ·
I took a look at it yesterday, theres lots of trimmings and things floating around the gas tank, the fuel filter is crammed full of things. The air filter and plugs were gross. The carb needs a good soak too. I will try these quick easy fixes first, than run it again for an extended period in order to see if there is still power loss.
 
#4 ·
Sounds like my daughter's old mower........:nonono:

It's amazing how many grass clippings can end up in the fuel tank.....I've seen plenty of clippings in fuel lines leading from the tank. Then, people wonder why their mower doesn't run the way it should. I always clear the area around my fuel caps (I have two tanks) and all gas can lids/spouts.

Good luck, FPM........I think you found the problem with your Deere.
 
#5 ·
Fortunately the fuel pickup tube is a bit above the bottom of the tank in a John Deere, which allows for some sand and other debris to settle without causing much of an issue. Periodically I use an oil syringe to suck the stuff out. I also replace fuel filters quite often, it take only a minute to do this and they hardly cost anything.

The air filter gets changed once a year and just blown out every couple of months. After reinstalling the air filter I blow dust out from under the cooling fan intake and blow the gas cap hole clean too. Oil and its filter are once a year but I lube about four times a year. I Seafoam about once a year then take the plugs out and clean/regap or replace them as necessary (I've actually only replaced them once). My 125 has 600 hours on it and still runs great.

 
#6 ·
This LA125 has 600 hours on it as well coincidentally.

UPDATE: Okay, so over the weekend I put in 2 new plugs, properly gaped. New air filters, new fuel filter (it was disgusting) I drained all the gas in the tank (there was a ton of leafs and things in there) Cleaned it, put fresh gas in. Did oil and oil filter. Cleaned all fins, cleaned everyone, checked hole in gas cap. Its certainly idling much better, it sounds better and has a bit more GO in it when just driving around but the issue from previous is still there....

What happens is that after 15-20 minutes of cutting, (actually using the deck, or under "load" so to speak) the motor loses almost all power. Does not shut off, but reverse becomes super slow mode reverse, and forward the same thing.

Any recommendations? Where to next?!
 
#7 ·
reverse becomes super slow mode reverse, and forward the same thing.
Have you checked the hydraulic fluid level? Also, check to see that the cooling fan is still there and turning properly.

Make sure the drive belt is properly adjusted too. A lose belt may slip when it becomes hot and expands.

Also, valve adjustments are relatively easy and should be done every couple hundred hour or so.
 
#12 ·
Okay so, today I got the deck off and everything seemed fine there, mower belt looks a bit worn so ill change that just because. Now I have the deck off, and ive went under what should I be looking for?

1. Is there a way to check the fluid in the transmission?
2. How can i tell if the drive pulley, or belt or any of the linkages are out of whack? They all seem tight and fine, the belt and brake so on seem good...
3. There is a electrical sensor or something of that nature plugged into the transmission, could this cause issues?!


What should i be looking for under the mower with regards to my problems?

Also Product Number on side of frame was: GX0120A044346 if that helps!
 
#13 ·
Completely lost now. Now the effin thing wont start. I have DONE NOTHING to this mower since it arrived here friday except remove the deck. After that it wont start, i had disconnected the battery and now it doesnt start. It has to be boosted so any ideas there?

It also will stall the minute you press down on reverse. Now the steering weel appears to be jumping gears down the shaft when you try and turn the tires.

Like I can fix cars, atvs, snowmobiles but im about ready to roll this Deere into Deere because im completely fu%#^#d here.
 
#14 ·
Okay yeah, well that was what was happening as well as the fuse being blown. So the motor is starting each time now again. No problems there, the issue with turning right is the teeth on the plate bolted to the bottom on the right turn side are worn completely off. That seems like an easy fix.

Now i ran the mower for an hour PLUS. And cant seem to recreate this guys issue. I am presently uploading a video i made showing all the under workings and such so perhaps when that is ready yall can watch it and see if you can notice or hear anything of note.
 
#16 ·
Nice video........:thumb:. Watch out standing on your head like that.......blood rushes to your head.......:laugh:. I can't do that......beard falls into my eyes and blocks vision.

Sounds good and looks ok.......but check the rear wheels. RR seems to be running faster than the left.......also looks like it's not running true. I'll take a few more looks at the vid.......I've only watched it three times.....:grin:

While you have the deck off take the thing for a ride.......can't tell much unless you put it under working conditions. Ride it around and let the transmission come up to operating temps and see if it becomes sluggish.......an incline would put a little more stress on the drive system and may produce symptoms. The guy did say it ran fine the first 20mins or so and then kinda bogged down?? If nothing happens put the deck back on and do it again.

The steering rack looks like an easy fix......I've done a few on my mowers.

Latest steering problem for me was a little more involved. Full hydo system (pumps and hyd motors) and the LH pump took a dump.......only $200 for me to rebuild and flush/change fluid and filter.
 
#18 ·
Make believe you're on an oval race track........nothing but left hand turns......:grin:

The owner must like getting all the clippings in a neat pile if he wore out the right side of the steering rack. I thought most decks have a RH discharge chute......
 
#21 ·
Remember that belts stretch over time and there also is some room for adjustment so measuring your old belt is just a rough estimate of what you need. Someone could have put the wrong belt on too.

According to the John Deere parts catalog, the drive belt for a LA120 is the 88.9" model GX20006. The 42" deck belt is the 103.3" GX20072.

I've had good luck buying my belts on Amazon. If they are the wrong size you can just use the website to return the item, the next day a UPS guy will pick it up no charge and your credit card will either be reimbursed or the replacement sent.
 
#25 · (Edited)
It sounds like it's running well and the belt doesn't seem to be slipping. If it were slipping one would think that it would do it immediately after load. Howerer, there is the possibility that the belt only slips after it's warmed up too.

Have you checked the compression and adjusted the valves? Sometimes a mis-adjusted valve will be worse when the engine gets hot.

Make sure that you clean well under the cooling screen at the top of the motor. My 125 was having trouble restarting and I found that a lot of grass and dirt had built up under there over the years, which was causing the engine to overheat.
 
#26 ·
I've done more research on this mower than I wanted to.......but, I now know enough to warn friends away from a mower with the T40 Tuff Torq transmission. I also think I know why I see quite a few JD's sitting in yards with a For Sale sign......and people still keep buying them for the JD name and reputation.

Best thing that should possibly be done with this series of mower is to change the transmission fluid every 100 hours unless you are using it on absolutely flat terrain with little load. Even then, it might be wise to change it on a regular basis.

The T40 can be serviced but it was intended to last the life of the mower without being serviced. That being said, fluid changes weren't intended and to change the fluid you will need to remove the entire transmission (transaxle). Step #4 and steps after #30 will apply in the following pdf file: https://www.tufftorqservices.com/En...Info/docs/repair/axlereplacementprocedure.pdf

One of the axles appears to be bent so you may want to follow the whole pdf if the owner wants to sink that much money into the machine.

Changing the transaxle oil may offer short term relief but from what I'm seeing don't count on it......:frown:

If your transmission is having loss of power or no drive when it reaches operating temperature, it is likely that the cylinder blocks and center case need to be replaced. When replacing any of these components, it is critical to replace all components to include 2 cylinder block assemblies with new pistons and springs, and the center case.
https://www.tufftorqservices.com/EnvEEdefault/FlatHTML/TechInfo/help/helplosspower.html
 
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