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Riding Mower Gas in Oil Repair - Replace Carburetor

Getting Started: Tools Needed to Replace Carburetor

Keep in mind, no riding mower is the same. The tools shown below are the most common tools you will need to complete the work. However, like in the case of repairing my riding mower, an old John Deere Sabre 1646 model, the repair did not go as simple as it should have. I will detail this later in the article.

  • Screw Drivers
  • Torque Wrench
  • Sockets that fit your mower, shown are 8mm, 10mm, & 11mm
  • Needle Nose Plyer
  • Vise Grip Plyer

Other Tools & Safety Not Shown:

  • Rotary Tool
  • Safety Glasses
  • Towels
  • Latex Gloves (Unless you desire to smell gas on your skin for days.)
  • Oil (Use what is recommended for your engine by the manufacturer.)
  • Oil Filter

Tools Needed

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Objective

The objective of this hub is to help with identification, removal, and replacement of a carburetor. This hub will not show you how adjust the carburetor or how to properly refill the oil. Please be sure to research the how to, if you are not aware of how to set the air/fuel mixture and the proper refill of oil. Also, not shown is the recommendation of replacing the air and fuel filters. Parts should only be replaced when engine is cool and not hot.

This hub is also assuming you will be comfortable in reassembly of parts after disassembly. Such as bolts being properly torqued, gaskets replaced, etc.

Carburetor Failure Signs:

  • Fuel/oil mixing (my issue)
  • Loss of power
  • Stalling and/or black smoke from exhaust
  • Backfiring or overheating
  • Starting hard or not starting

Location of Carburetor

riding-mower-gas-in-oil-repair

Carburetor Location

Typically carburetors are located on the broad side of the engine. In my case it is on the left side facing from drivers wheel. Be sure to clamp off or close off the fuel to the carburetor before disassembly. The carburetor will still have some gas left in it, so use caution. This job should be done in a well ventilated area and nowhere near a fire source.

Remove Fuel Line

riding-mower-gas-in-oil-repair

Removal of Fuel Line

When removing fuel line, have an empty tank of gas, clamp off line, or have a fuel cut off valve in the closed position. Otherwise, gas will just flow freely after the line is removed. Suggested to have something to catch the fuel that is left in the line and also a rag to minimize the mess and hazard. My lines were attached with clamps that are easily removed with a vise grip plyer. You may need a flat head screw driver to pry off the fuel line from the carburetor intake once the clamps are moved away.

Remove Air Filter and Housing

riding-mower-gas-in-oil-repair
riding-mower-gas-in-oil-repair

Removal of Air Filter House and Air Filter

The air filter housing and air filter should have two separate hand screw nuts holding them in place. The air filter above is clogged with oil due to the failure of the carburetor. It was replaced (not shown.)

Drain Old Oil

riding-mower-gas-in-oil-repair
riding-mower-gas-in-oil-repair

Oil/Gas Mixture Removal

Typically replacing oil is not necessary if replacing the carburetor is being replaced for another reason. In my case, the oil is well mixed with the gas and is thinned as seen in above photo. Never run an engine with oil that is mixed with gas, it will eventually ruin the motor. During the course of the hour in replacing the carburetor, I let the oil drain to where there was nothing dripping. This allows for new oil to take over. Be sure to use the recommended oil & oil filter for your specific riding mower engine. As always, please properly dispose of the old oil at your local oil recycling facility.

Remove Solenoid Wiring

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Remove Screw and Bolts

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riding-mower-gas-in-oil-repair

Intake Manifold Bolts and Air Housing Bracket Screw

For this engine, when replacing the bolts later for the intake manifold, the torque value is 65 inch pounds. This may be different for your engine and you should refer to the manufacturer for proper specifications. Use a torque wrench to be certain you have not over or under applied torque to the bolts. This prevents leaks, accidental bolt breakage or worse, an engine block crack.

Note: When I removed the screw from the engine mount to air housing bolt, it stripped. Thus, I will need to repair this. In the end of this hub you will see that the bracket is not in place like it shows at the beginning of this hub. The repair is being done outside the scope of this hub.

Unhook Breather Hose and Throttle/Choke Bars.

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riding-mower-gas-in-oil-repair
riding-mower-gas-in-oil-repair

Note The Positions of the Throttle and Choke Bars

When removing the throttle and choke bars, take note to their position and placement. Taking a photo will help. Also, keep in mind the smaller adjustment spring around the throttle bar is somewhat fragile. Take your time in removing. In my case, after removing all bolts from carburetor mount points, I rotated the entire unit to the right, thus allowing easy removal of the bars.

Remove Air Filter Housing Mount

riding-mower-gas-in-oil-repair
riding-mower-gas-in-oil-repair
riding-mower-gas-in-oil-repair

Remove Nuts/Bolt from Air Filter Housing

This particular air filter housing only had one upper bolt holding it down to the carburetor and two bolts attached to long bolts that go through the carburetor. The lower nuts later will be torqued to 65 inch pounds. The air housing bolt is hand tight. See manufacturer specifications for appropriate torque values for your engine.

Remove Throttle/Choke Bars & Long Bolts

riding-mower-gas-in-oil-repair
riding-mower-gas-in-oil-repair

Removing Long Bolts and Throttle/Choke Bars

Remove the throttle/choke bars first. Again, be patient and gentle with the smaller spring on the throttle bar. Throttle/choke bars are not typically included in a carburetor kit and have to be purchased separately. Thus if broken or damaged, could put a delay on your repair being completed.

The long bolts that pass through the carburetor will later be reapplied at 65 inch pounds per the specifications of this manufacturer.

New Carburetor Installed

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riding-mower-gas-in-oil-repair

New Carburetor & Bars ReInserted

The above replacement carburetor is shown bolted back to the intake manifold and throttle/choke bars reattached. From this point I thought I was home free until I attached the air filter housing. I noticed the the choke plate would not open and close freely.

In the next photos, you will see I had to modify (shave) down some of the air housing internal airway. I also had to remove a plastic cylinder that was near the choke bar. This is no doubt due to a need for a different mower that takes the same carburetor, however has attachments or configurations. A rotary tool was used for grinding down the plastic with fine sanding. You do not want to take off any more than necessary.

Modifications / Retrofit

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riding-mower-gas-in-oil-repair

Installed and Finished, Almost

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Final Steps

After reassembly, your engine will likely start, however no carburetor comes perfectly set for air/fuel mixture and idle control. So here are the final things to do:

  • Refill Oil
  • Turn on fuel flow if clamped or cut valve is in use.
  • Adjust air/fuel mixture and idle control via valves on carburetor.

The adjustment of a carburetor fuel/air mixture and idle control will need to be set per your manufacturer's recommendations. There are plenty of videos online that explain how to do this. Do not run your engine for use until these valves have been adjusted. Using the out of the box carburetor factory settings can cause poor engine performance, over idle rpms, too much fuel, backfiring, etc.

Hope this hub helps with the replacement of your carburetor. Typically, it shouldn't take more than 2 hours if there are not complications.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2021 Ryan Hutzel

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