Small Engines (Lawn Mowers, etc.)/318 wont stay running


I have a john deere 318 with a B43G engine it had been running great then one day it started to die then gradually got worse it wouldnt stay running. I pulled it into the garage and change plugs wires and filters and checked the compresion all is good, still wont stay running it will start then die. I can put my hand over the top of  carb and it will run for awhile when I take my hand offf the top of the carb it will die. I dont want to just keep changing parts do you have a starting place for me.

I would start by removing, dis-assembling and cleaning the carburetor based on the symptom you described.  When you place you hand over the carb you are reducing the amount of air entering the fuel system and increasing the fuel which tells you the engine is running very lean...not enough fuel.   This could be caused by a dirty carb or an intake leak.  

Cleaning carbs is the most common repair to fix your problem.

You can search You Tube for Onan B43G carburetor or small engine carburetor cleaning and find lots of videos on performing small engine carburetor cleaning.  After viewing a few videos you can decide if you want to tackle the job yourself.

You will need an air compressor and an empty or old gas can if you need to drain the entire fuel system but other than basic hand tools there are no other special tools you need to clean the carb.  Taking digital photos as you remove and dis-assemble the carb will help when you go to put it back together.

DO NOT mess with the governor!  Just mark how the throttle rods/links connect to the carb so you know which holes to put them back in when you re-install.

Let me know if this helps.

Small Engines (Lawn Mowers, etc.)

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Eric A. Jones


Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.


Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

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