Briggs & Stratton 799871 Carburetor | Repair Guide
The Briggs & Stratton 799871 (also sold as 790845) carburetor powers millions of 190cc push mowers across America. This carb shows up on Troy-Bilt, Murray, Yard Machines and dozens of other brands using the Briggs 675 and 725 Series engines. When your mower struggles to start or runs poorly, this guide walks you through diagnosis and repair.
Table of Contents
- Engine and Equipment Fitment
- Identifying Your Carburetor
- Common Failure Symptoms
- Step-by-Step Replacement
- Carburetor Cleaning Guide
- Troubleshooting Specific Issues
Engine and Equipment Fitment
The 799871 fits Briggs & Stratton 190cc vertical shaft engines. You’ll find these on:
Walk-Behind Mowers:
- Troy-Bilt TB110, TB200, TB230
- Murray 21” push mowers
- Yard Machines 140cc-190cc models
- Bolens 140cc-190cc mowers
- Craftsman 675 EX Series
- Snapper 21” push mowers
Engine Series:
- 675 Series (190cc)
- 725 Series (190cc high-torque)
- Engine family 09P7xx
Model Numbers Starting With:
- 093J00
- 09P702
- 09P772
- 093312
[NEED REAL IMAGE: Engine model number location on 190cc Briggs & Stratton]
The number is stamped on a metal tag or directly into the blower housing above the muffler.
Identifying Your Carburetor
Several part numbers interchange:
| Part Number | Status |
|---|---|
| 799871 | Current |
| 790845 | Superseded |
| 799866 | Different - NOT interchangeable |
| 796707 | Older version |
Important: The 799871 and 799866 look similar but are NOT the same. The 799866 fits larger 6.5-7.25HP engines. Check your engine specs before ordering.
The 799871 has:
- Plastic primer bulb on top
- Single mounting bolt (center)
- Integrated choke plate
- No external adjustment screws
Common Failure Symptoms
Won’t Start - Most Common
You prime it, pull the cord and nothing happens. Maybe it pops once then dies.
Typical causes:
- Varnished fuel passages from stale gas
- Clogged main jet
- Failed primer bulb
- Stuck float needle
Starts Then Dies
Engine fires up for 2-3 seconds then quits. Priming again gets another brief run.
Typical causes:
- Blocked fuel flow to the main circuit
- Partially clogged jet
- Float stuck in closed position
Surging and Hunting
Engine runs but constantly speeds up and slows down without touching the throttle.
Typical causes:
- Lean fuel mixture (restricted fuel delivery)
- Air leak at carburetor gasket
- Governor linkage binding
Runs Rich - Black Smoke
Engine belches black smoke and fouls the spark plug quickly.
Typical causes:
- Stuck float needle (open position)
- Sunk or punctured float
- Wrong float height
Fuel Leaking
Gas drips from the carburetor body or primer area.
Typical causes:
- Cracked primer bulb
- Failed bowl gasket
- Needle valve not seating
Step-by-Step Replacement
Total time: 15-25 minutes
What You’ll Need
- 3/8” socket
- 10mm socket
- Flathead screwdriver
- Needle-nose pliers
- Shop rags
- New carburetor (799871)
Procedure
1. Safety First
Disconnect the spark plug wire. Pull it off and tuck it away from the plug.
2. Remove Air Filter Cover
Usually one screw or a wing nut. Lift off the cover and remove the foam or paper filter element.
[NEED REAL IMAGE: Air filter removal on Troy-Bilt/Murray mower with 190cc engine]
3. Note the Linkage Positions
Take a phone photo before touching anything. The throttle cable and governor spring positions matter for reassembly.
4. Shut Off Fuel
Clamp the fuel line with locking pliers if there’s no shutoff valve. Position your rag under the carb.
5. Remove the Single Mounting Bolt
One bolt (usually 3/8”) holds this carb to the engine. Support the carb with your other hand.
6. Pull Carburetor Away
It’ll slide off the intake tube. Disconnect the fuel line (have that rag ready).
7. Unhook Linkages
The governor spring and throttle link disconnect from small holes in the throttle lever. Note exactly where they connect.
8. Remove Old Gaskets
Peel off old gasket material from the intake tube. Inspect for any chunks that might fall into the engine.
9. Install New Carburetor
Slide new carb onto intake tube with new gasket. Start the mounting bolt by hand to avoid cross-threading.
10. Reconnect Linkages Per Your Photo
Spring tension and linkage positions control engine speed. Get these wrong and the mower won’t run right.
11. Reattach Fuel Line
Push it on firmly. Check for kinks.
12. Prime and Start
3-5 primer pushes. Should fire within 2-3 pulls if everything’s connected correctly.
Carburetor Cleaning Guide
Cleaning often restores a gummed-up 799871 without replacement.
Disassembly
1. Remove float bowl
One screw on the bottom. Catch any remaining fuel.
2. Remove float and needle
Push out the float hinge pin. Lift out the float and attached needle valve.
3. Remove main jet
On this carb, the main jet is often pressed into the center post. If it’s removable, use a flathead screwdriver. Don’t force it if it won’t budge.
[NEED REAL IMAGE: 799871 carburetor disassembled showing float bowl, float, needle]
Cleaning
1. Soak all metal parts
Use carburetor cleaner or Berryman Chem-Dip. 30 minutes minimum. Overnight for heavy varnish.
2. Clear all passages
Compressed air through every hole. There are tiny passages you can’t see - blow air through all of them.
3. Clean the main jet
If removable, run a strand of wire through it. Carb cleaner spray first, then air.
4. Inspect needle valve tip
The rubber or viton tip should be smooth, not grooved or hardened. Replace if damaged ($5-8 kit).
Reassembly
1. Install needle valve in float
The clip should secure it firmly.
2. Set float height
With carb inverted, float should be roughly parallel to the carb body. There’s no precise adjustment on this model.
3. Install float bowl with new gasket
Use the gasket from your rebuild kit. Don’t reuse the old one.
Troubleshooting Specific Issues
Issue: Engine Starts Cold But Not Hot
What’s happening: Fuel percolation or primer system failure
Check:
- Primer bulb condition - cracks mean it’s not creating vacuum
- Fuel line routing - should stay away from muffler heat
- Air filter condition - dirty filter causes rich running
Fix: Replace primer bulb and check fuel line routing
Issue: Only Runs on Choke
What’s happening: Main jet clogged, engine starving for fuel
Check:
- Main jet - clean or replace
- Fuel filter - could be restricted
- Tank vent - cap should allow air in
Fix: Clean main jet thoroughly or replace carburetor
Issue: Flooding - Gas Pouring Out
What’s happening: Float needle stuck open
Check:
- Float for damage or sinking
- Needle valve tip condition
- Debris on needle seat
Fix: Clean needle seat thoroughly. Replace needle if tip is worn. Check float by shaking it - you shouldn’t hear fuel inside.
Issue: No Fuel in Bowl After Priming
What’s happening: Fuel not reaching carburetor
Check:
- Fuel shutoff valve (if equipped)
- Fuel line for kinks or blockage
- Fuel filter
- Tank - is there actually fuel in it?
Fix: Work backward from carb to tank checking each component
Aftermarket vs Genuine
Genuine Briggs 799871: $35-50 Aftermarket: $12-20
Aftermarket carbs work for many people. Common issues:
- Slight fitment differences
- Primer bulbs fail sooner
- Float quality varies
For a mower you’ll keep 5+ years, genuine is worth it. For an older mower or temporary fix, aftermarket does the job.
Preventive Maintenance
Keep this carburetor healthy:
- Use fuel stabilizer - Add Sta-Bil or similar to every tank
- Run dry for storage - Shut off fuel and let engine die
- Fresh fuel only - Don’t use gas older than 30 days
- Change fuel filter annually - $3 insurance policy
- Store inside - Condensation causes corrosion
Frequently Asked Questions
Can I use 799866 instead of 799871?
No. They look similar but have different throttle bore sizes and mounting configurations. Use the correct number for your engine.
Why does my new carb leak from the primer?
The primer grommet or o-ring wasn’t seated properly. Remove primer bulb and reinstall, making sure the o-ring sits in its groove.
How often should I rebuild vs replace?
First failure: try cleaning and rebuild kit ($10). Second failure: replace the whole carb. Time is money.
My aftermarket carb won’t fit right. What now?
Return it. Aftermarket quality varies. Try a different brand or go genuine.
The 799871 is a simple carburetor. Most problems come from stale fuel. Use fresh gas, add stabilizer and you’ll rarely need to touch it.