Engine Lawn Boy Model 10525 Engine Problems

I have a Lawn Boy Gold Pro Series with a 6.5 HP 2-cycle Duraforce engine. It has an aluminum deck and was an expensive mower but the engine has not been reliable. I have had it for about 7-8 years and mow less than a 1/2 acre around my house with it. Each summer I have to take it in for servicing. They claim it suffers from dirty gas. However they installed a filter on it and it still suffers from the same problem. It will run and then the engine rpm starts to oscillate and then drop off. Sometime I can keep it running by placing a little choke. I use high test gasoline with no ethanol and a 32-1 gas to oil mix with Lawn-boy oil. Now it won't start at all.

Are these 2-cycle Lawn-Boy mower engines particularly prone to carburator problems? I am getting tired of working on this mower each season.

Try this, on the side of the carb is a jet that gets dirty. It may be under a sticker. Remove this jet and give it a good cleaning. The holes are very small, especially the one going down the center. Also, spray carb cleaner into the port where you took the jet out. Reinstall it and report back.

I ended up taking the carburetor apart and cleaned the needle valve as you suggested along with everything else. I looked at drawing of the carburetor on PartsTree.com and found that there is supposed to be a small filter element inside the carburetor but it was missing.

I also noticed that the air vane did not move freely and the spring was binding it up. I tried to pull it apart but ended up breaking the air vane to access the spring. I'm new at this, but determined. I'm anxious to get the parts and will report out again, when I get it back together, and give it pull on the starter cord. I have paid $75 to rebuild the carburetor at a local sales/service shop, so if this works, I can affort to learn from my mistakes and justify buying perhaps a few replacement parts that I might not truly need.


I ordered the following parts from PartsTree.com:

Part ID Description Quantity Unit Price Subtotal
TLB 94-5787 Filter-Fuel 1 1.09 1.09
TLB 98-7011 Spring-Throttle 1 0.83 0.83
TLB 104-4430 Air Vane 1 5.98 5.98
TLB 66-7460 Bulb-Primer 1 2.21 2.21
TLB 50-1170 Spark Plug 1 6.51 6.51
TLB 94-5795 Intake Gasket 2 0.65 1.30
TLB 95-7613 Gasket-Filter Base 1 2.09 2.09

On this site you should find a manual to help you. Let us know what happens.

https://lookup3.toro.com/ttcGateway/acrobat/manuals/lball.html

I cleaned out the carburetor and the main jet was indeed dirty. When I looked at the parts diagram, I found that there was a screen part missing that is supposed to keep debris out of the main jet. Unfortunately, when I put everything back together, it still would not start. I am getting gas to the spark plug, but now I am not getting any spark. At least my wife claimed she did not see any spark when I pulled the cord. I didn't see any spark when she pulled the cord either, but she is not capable of giving it a very good pull. The spark plug was brand new. I also tried another new spark plug but it never once fired off. I am now suspicious of the electronic ignition. Should I purchase the following part?

Parts Tree Diagram part #18 Diagram: 10525%2C+GoldPro+Series+Lawnmower%2C+1998+%28SN+8900001-8999999%29 ENGINE ASSEMBLY TLB Lawn Boy 99-2916 (replaces 92-1152)
Ignition ASM Your price: $52.55

Kelch said:

I cleaned out the carburetor and the main jet was indeed dirty. When I looked at the parts diagram, I found that there was a screen part missing that is supposed to keep debris out of the main jet. Unfortunately, when I put everything back together, it still would not start. I am getting gas to the spark plug, but now I am not getting any spark. At least my wife claimed she did not see any spark when I pulled the cord. I didn't see any spark when she pulled the cord either, but she is not capable of giving it a very good pull. The spark plug was brand new. I also tried another new spark plug but it never once fired off. I am now suspicious of the electronic ignition. Should I purchase the following part?

Parts Tree Diagram part #18 Diagram: 10525%2C+GoldPro+Series+Lawnmower%2C+1998+%28SN+8900001-8999999%29 ENGINE ASSEMBLY TLB Lawn Boy 99-2916 (replaces 92-1152)
Ignition ASM Your price: $52.55

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Before you buy a new ignition unit try baking it in an oven ( :laughing: no kidding... it works sometimes). There's at least one thread with more detail about that. If you can't find the thread, let me know and I'll find it.

First, I would remove the kill switch wire from the ignition module and check for spark again. If you still have no spark you will have to replace the coil. Not a fan of baking.

Okay, I removed the kill switch wire and checked for ignition with an ignition tester. There was definitely no ignitor voltage going to the spark plug. I ordered the ignition assembly from Parts Tree.com. I will be out-of-town for a week or so and will not be able to work on this until the first of November. I will let you know how that turns out. Thanks for your guidance.

I replaced the ignition harness and the mower is working well now except the throttle is not adjustable. The engine rpms do not respond to the throttle lever. However, I always operate the unit at full throttle anyway. Thanks for the guidance received on this web site.

Kelch said:

I replaced the ignition harness and the mower is working well now except the throttle is not adjustable. The engine rpms do not respond to the throttle lever. However, I always operate the unit at full throttle anyway. Thanks for the guidance received on this web site.

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You can check the governor spring and make sure it's attached. The plastic piece the cable attaches to may be broken.