Surging is a royal pain in the ass; this page has you covered. There’s a video for each of the more common walks behind lawn mower engines. Surging is most commonly caused by a gas supply restriction, and that is usually caused by a dirty carburetor. The videos on this page are dedicated to cleaning your carburetor.
You’ll find useful resources at the bottom of the page, tips, and links to tools, parts, and supplies required to complete your repair.
All mowers suffer from carburetor problems and surging or erratic idle; it’s a common story. However, other causes of surging should be eliminated before cleaning the carburetor. Go ahead and drain the carb bowl, remove, clean and gap or replace the spark plug, check if the gas is fresh, is the air filter OK?
Having eliminated these, it’s time to clean the carburetor idle jet. Many mowers will allow easy access to the idle jet, and for others, we’ll need to remove the carburetor.
Surging or erratic idle may also be caused by a faulty carb or vacuum leak. Vacuum leaks are commonly caused by bad carb gaskets or cracked manifolds. These videos show the complete job start to finish for many common engine types.
Before working on your mower be sure to remove the plug wire to prevent accidental starting, see “Repair Safety Video”.
Briggs & Stratton (Classic) Surging Repair
This video walks you through the surging repair of a very common B&S (Classic/Sprint/Quattro engine) surging cause. A bad spark plug can be the route of many problems, be sure to check the plug before performing carburetor work.
This type of carburetor is famous for surging and it’s caused not by a dirty carburetor but by a damaged carburetor diaphragm gasket which allows a vacuum leak, which in turn, causes the engine to surge.
In this video, we’ll remove the carburetor, strip, clean, replace the gasket and refit the carburetor.
Briggs & Stratton Manifold Replacement
This video covers the replacement of the B&S (Classic/Sprint/Quattro engine) manifold. It’s another common cause of irritating engine surges. If you have replaced the gasket as per the video above and dame it!, it’s still surging, you need to replace the manifold pipe.
Briggs & Stratton (Intek) Surging Repair
This video covers the repair of a surging Briggs & Stratton Intek engine. The carburetor fitted to both the Intek and Quantum engines employ a carburetor bowl fastener with an integrated jet, its unique setup.
When the bolt clogs with grit, it can cause a surge. The great thing about this setup is removing and cleaning the bolt usually solves the problem. So before removing the carburetor, try cleaning the bowl bolt first. Anyway, it’s all covered in the video.
Briggs & Stratton E Series Surging Repair
This video covers the complete surging repair of the Briggs and Stratton E series engine. It’s one of Briggs’s latest engines and fitted to many mowers. The carburetor is plastic and the fine jets block easily, quite the pain actually. Anyway, the video covers the whole story, don’t be surprised if you need to replace the carburetor jet module.
Kohler Engine Surging Repair
This video covers the complete repair of a surging Kohler engine. Kohler engines are easy to work on and in many cases, just a few minute’s works solves the problem. One of the easiest surges to fix, lucky you!
Honda Surging Repair
This video covers the complete repair of a surging Kohler engine. Honda engines are usually pretty easy to work on, but in truth removing the carb is a bit of a pain.
Avoid removing it unless you’re left with no choice. Luckily the Honda carb employs an idle jet which is accessible without removing the carburetor. The idle jet is famous for blocking and causing a surge. Clean it and test before removing and cleaning the carburetor.
The video below covers the whole repair.
Tools & Resources
To nail this procedure you may need the following tools, parts, and supplies.
Briggs & Stratton – Most models take from empty .65 US quarts (.6 lts) 5W30 engine oil.
Honda engines – Most take from empty .58 US quarts (.55 lts) of 10W30 engine oil.
Kawasaki engines – Most take from empty .6 US quarts (.6 lts) 10W30 engine oil.
Kohler engines – Most take from empty .6 US quarts (.6 lts) 10W30 engine oil.
For exact specs see:
Briggs & Stratton walk behind mower
Briggs & Stratton tractor engine
This is first on the list for good reason, WD solves a ton of problems. I won’t work without it, because I can’t. Picture links to Amazon.com.
Ratchet Tool Set
Before we can do anything, we’ll need tools. I’ve selected this set as I own some Craftsman tools and while I have worn some out, they did do a lot of work. So I expect this set will last the occasional user quite a long time. This set carries both metric and standard sockets and that’s important because some mowers will have both types of fastener sizes. Set includes spark plug sockets. Picture links to Amazon.com.
Gas & Oil Syphon
You’ll find this tool really useful if you need to drain the gas tank, and you will if the gas is stale. The siphon will remove it without fuss or mess and it can be used for extracting the oil too. Picture links to Amazon.com.
Gas Line Clamp
Some small engines will have a gas tap, which is really handy when removing the carburetor, stops gas flowing all over the shop. However most engines won’t have one, these useful clamps simply squeeze the fuel line and prevent a spill while you perform surgery. Picture links to Amazon.com.
When cleaning your carburetor you’ll need this stuff. Gumming is a sticky substance that’s hard to shift. The carb cleaner will remove it, however, if your carb is really bad, save yourself some work, go ahead and buy a new carburetor. Picture links to Amazon.com.
You’ll find these nylon brushes super useful when it comes time to clean those tiny passageways of the carburetor and jet. Use these in conjunction with the WD Carb cleaner. Picture links to Amazon.com.
Mix this with the gas when winterizing your small engine. Gas isn’t what it used to be, it goes stale, in some cases after just one month. Bad gas causes gumming and that’s a carburetor killer. A stabilizer will save you money and stress in the long run. Picture links to Amazon.com.
Briggs and Stratton refuel can. These guys got it right, I like it a lot, it offers press button control, no fuss no mess and no funnel required. Picture links to Amazon.com.
Every home needs a Dvom (Digital Volt Ohm Meter). It’s used to check for continuity in lawn mower wiring, and for voltage when there’s a battery fitted. But don’t use this tool to check spark, that will kill it. I use mine every day. I have the previous model to this and it’s still doing its job. Picture links to Amazon.com.
Now, this tool is a must-have if you’re removing the flywheel. Why would want to remove the flywheel? Sometimes the flywheel key shears, it stops your engine from starting. The key is really cheap and it’s easy to fix when you’ve got this tool. Picture links to Amazon.com.
Tap & Die set
Used to cut threads. Many flywheels are not threaded which is a right pain in the jacksie, but this Gearwrench kit makes short work of threading. I especially like the ratcheting T handles. Picture links to Amazon.com.
This tool is used to check both the spark plug and the coil for spark. Sure you can check the spark without the tool, but it’s not as good, the tool is designed to stress the whole ignition system. Picture links to Amazon.com.
The ABN 26 blade feeler gauge set is marked in SAE and metric. You’ll need this set to adjust valve lash and is useful when setting armature/coil air gap. You can also use it to gap spark plugs. Picture links to Amazon.com.
Plug Gapper Tool
This tool isn’t strictly necessary if you have a feeler gauge, but it’s a lot easier to handle. If you haven’t guessed. You use this tool to check the gap of your spark plug, a simple effective tool. Picture links to Amazon.com.
This is a compression tester, it’s fitted in the plug hole using the adaptor. Cranked over the engine allows the gauge to capture the compression which is read on the dial. A low reading can be caused by a simple fault such as a sticking valve. Picture links to Amazon.com.
The OTc is quality kit and will last many years of use. A leak-down tester will require compressed air. The tester measures how much air escapes a cylinder and helps you find weak rings, valves head gaskets etc. Picture links to Amazon.com.
I love DeWalt, they make quality tools. This heavy-duty but lightweight 1/2 inch impact wrench makes short work of stubborn bolts like flywheel nuts and rusty blade fasteners. Up to 700 ft-lbs of torque on tap, I keep one in the trunk of our family car, which makes a flat almost enjoyable. Picture links to Amazon.com.
I use a Dewalt screw gun (also a drill) in the workshop to speed up the process of removing engine covers, carburetor bolts, Armature bolts etc. It’s a brushless motor and as tough as nails, I drove over it a few times – still works great! Batteries are interchangeable and so if you have a Dewalt product already you won’t need the battery. Picture links to Amazon.com.
Teng 1/2 Torque wrench, a fantastic tool I use it every day, and mine is still going strong. A torque wrench is advised for tightening components such as flywheel nuts and blades. The torque spec of these components is very important. Picture links to Amazon.com. If you’re buying a torque wrench, check out my review of Teng torque wrench, it’s the torque wrench I use.
Briggs & Stratton
This is a popular Hooai Carburetor fitted to walk behind mowers with Quantum engines, but check the engine codes listed. This is an Auto choke carburetor. This carburetor has a fuel feed bolt in the base of the bowl, dirt in the bolt feed hole is a common issue. Picture links to Amazon.com.
Briggs & Stratton
This is an after-market replacement carburetor for the Briggs 4-7hp engines. This is the primer bulb-style carburetor. This carburetor has a fuel feed bolt in the base of the bowl, dirt in the bolt feed hole is a common issue. It comes with a replacement air filter/primer bulb housing gasket. Without this gasket, your primer bulb won’t work. Picture links to Amazon.com.
Briggs & Stratton
This is an original Briggs carburetor fitted to walk behind mowers. Part # 593261, these guys are made from plastic and I see lots of issues with them. The jet holes are particularly tiny and block so easily. There are a few different types and all look alike, so use part numbers to check before ordering. Picture links to Amazon.com.
Briggs & Stratton
This is a popular carburetor fitted to the classic range of Briggs and Stratton engines. This engine is fitted to many different walk-behind lawn mower models like MTD, TORO, Murray, Poulan, Craftsman, and many more. Picture links to Amazon.com.
Honda GCV 160
This is a Hooai carburetor fitted to the Honda GCV160 engine only, not the GVC190. It comes with gaskets, a plug, filter, and a fuel line. Fitting isn’t difficult, just a little tedious, take your time and some pictures of where the old gaskets are positioned and their orientation. Picture links to Amazon.com.
Honda GCV 190
This is a Hipa GCV 190 carburetor fitted to the Honda GCV190 engine only, not the GVC160. It comes with gaskets, plugs, filter, and a fuel line. Fitting isn’t difficult, just a little tedious, take your time and some pictures of where the old gaskets are positioned and their orientation. Picture links to Amazon.com.
Piston Stop Tool
Universal piston stop tool 10mm and 14mm, used to lock the crankshaft when removing and tightening the flywheel nut. Picture links to Amazon.com.
- About the Author
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John Cunningham is an Automotive Technician and writer at Lawnmowerfixed.com.
He’s been a mechanic for over twenty-five years and shares his know-how and hands-on experience in our DIY repair guides.
Johns’s fluff-free How-to guides help homeowners fix lawnmowers, tractor mowers, chainsaws, leaf blowers, power washers, generators, snow blowers, and more.