Simplicity lawn tractor losing power

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  #1  
Old 05-03-08, 04:16 AM
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Simplicity lawn tractor losing power

My Simplicity lawn tractor starts good, but when I turn on the mower deck pto and start cutting gas it loses power. If I slow down, the engine/mower deck will eventually regain speed. I just replaced a pulley in the mower deck which had bad bearings and it seemed to help a little. I did replace the plugs, one seemed normal, tan colored. The other plug was black.

The tractor is about 17 years old.
16 HP Briggs & Stratton engine, about 7-8 years old.
 
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  #2  
Old 05-03-08, 06:17 AM
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If you have eliminated binding, bad bearings, etc. I would adjust the valves and clean the carburetor. Clean the carburetor thoroughly and install a new carburetor kit. Unless the carburetor is severely gunked up I do not clean the by immersion in carburetor cleaner.

Here is how I would clean the carburetor:
If you have an Auto Zone parts store in your town, purchase a can of “Valucraft Carb Cleaner” Part Number: AZ-4, 13 ounces in a yellow and black aerosol can with a red plastic cap. It sells for around $2.50 per can. I have been very successful in cleaning carburetors with this cleaner. I have not had many carburetors I could not clean. Sometimes I use the entire can. At the price it sells for, so what.

WARNING - Do not get “Valucraft Carb Cleaner” in your eyes or on your skin. Use a full-face shield for eye and face protection. Wear protective gloves. The cleaner will damage rubber so remove rubber carburetor parts to prevent damage.

Valucraft Carb Cleaner will melt and wash away varnish. Spray as much cleaner as possible into the fuel passages. Follow up by blowing out with compressed air. Be sure to blow passages and everything else out after cleaning.

Float inlet needles will often drag or stick in a needle cavity that is dirty or corroded. Cleaning the carburetor can leave deposits that can cause the needle to drag. Needles often do not seat against the fuel inlet hole because of dirt or corrosion. This dragging, sticking or not seating will allow fuel to flow past the needle.

After cleaning of the carburetor I recommend you, polish the inlet needle cavity. With the plastic inlet seat removed, if installed, polish the needle cavity. I make a polishing tool using a wooden meat skewer with one end wrapped with NEVR-DULL metal polish. The wrapped tip should fit tightly in the needle cavity. Chuck the skewer in a drill and insert the end wrapped with the NEVR-DULL in the needle cavity. Operate the drill slowly several seconds and the needle cavity is usually clean and polished. If you do not have, NEVR-DULL use the metal polish of your choice.

After polishing the needle cavity, install inlet needle and float. Place a few drops of solvent or fuel on the inlet needle. Pressures test the needle seat by inverting the carburetor and applying 5-15 PSI air pressure to the fuel inlet fitting. A seat that functions properly should hold the pressure. Move the float with your finger and observe that it moves freely. If you do not have the pressure tool attach a hose to the fuel inlet fitting and gently blow through the hose.

I do this to every carburetor I rebuild and rarely have problems.

Good luck
 
  #3  
Old 05-03-08, 07:50 PM
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Thanks for the detailed response. I'll give it a shot and let you know how it works.
 
  #4  
Old 05-03-08, 08:32 PM
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Judging by the description of your problem, and the condition of your spark plugs, I'd say your engine is running on one cylinder. Check for spark on both plugs.
 
  #5  
Old 05-04-08, 06:37 AM
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Just checked for spark and it is only getting spark from 1 plug. What would you suggest next?
 
  #6  
Old 05-04-08, 09:59 AM
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Without knowing which Briggs engine you have, I'll assume you have a Twin Opposed and with such it will have just one ignition coil and you would then need to replace the coil (provided the plug lead has not been severed and exposing bare wire thus grounding out). Post back with engine ID numbers!
 
  #7  
Old 05-04-08, 01:47 PM
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Vanguard V-Twin
model: 303777
type: 1032-E1
code: 99020211

Looking at the repair manual it says about the ground wire harness, containing diodes, that if the engine runs on 1 cyl & shuts off ok, the cause is 1 closed diode.

Theres a way to test the harness but I guess you need a B&S multimeter, I have a regular multimeter but not sure if that will work.

So I was going to take it in and see if the shop can test it, or just by a new one and hope it works.
 
  #8  
Old 05-04-08, 11:10 PM
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You can do this with a regular multimeter, and a new diode from radio shack if needed. The diodes are in the kill wires and if one shorts out, it allows backfeed from one coil to the other. Try this, remove the engine shroud and unplug the kill wires from each coil. Then test for spark at each plug (don't start the engine, just check for fire). If you have fire at both plugs, then there is a problem with a diode or the kill wire. If you still only have fire on one plug, then the non-firing coil is bad.
 
  #9  
Old 05-06-08, 05:48 PM
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Replaced the coil today and the tractor is running good once again. Thanks for all the help.
 
  #10  
Old 05-06-08, 11:37 PM
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Good job, and glad we could help! Thanks for the update!
 
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