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Smoke Signals: A Video Guide to Diagnosing White Smoke in Your Mower

By: Author John Cunningham. Published: 2020/10/13 at 7:42 pm

This video walks you through the diagnosis & repair process step by step, including checking the oil level and removing excessive oil the easy way, checking compression, and fitting a new carburetor. Before working on your mower, be sure to remove the plug wire to prevent accidental starting; see “Repair Safety Video”

Resources

You’ll find useful resources on this page, tips, and links to tools, parts, and supplies required to complete your repair. White smoke is the drama queen of mower problems; sure, it looks bad, but it rarely is. The smoke is caused by oil mixing with gas in the combustion chamber. As the oil burns, it bellows white smoke.

Excessive oil in the cylinder is usually caused by:

  • Tilting mower wrong way
  • Overfilling oil
  • Faulty carburetor float needle
  • Blown head gasket
  • Engine rings worn

Briggs & Stratton – Most models take from empty .65 US quarts (.6 lt) 5W30 engine oil.

Honda engines – Most take from empty .58 US quarts (.55 lt) of 10W30 engine oil.

Kawasaki engines – Most take from empty .6 US quarts (.6 lt) 10W30 engine oil.

Kohler engines – Most take from empty .6 US quarts (.6 lt) 10W30 engine oil.

For exact specs, see:

Tools & Parts

WD40

This is first on the list for a 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. The 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 can be used to extract 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, and 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.

Carb Cleaner

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.

Cleaners

You’ll find these nylon brushes super useful when cleaning those tiny passageways of the carburetor and jet. Use these in conjunction with the WD Carb cleaner. Picture links to Amazon.com.

Gas Stabilizer

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.

Gas Can

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.

Compression Tester

This is a compression tester; it’s fitted in the plug hole using the adaptor. The gauge measures and captures the reading on the dial. A low reading can be caused by a simple fault such as a sticking valve. Picture links to Amazon.com.

Leak-down Tester

The OTc is a 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.

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 many 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, plugs, filters, and a fuel line. Fitting isn’t difficult, just a little tedious; take your time and take 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, filters, and a fuel line. Fitting isn’t difficult, just a little tedious; take your time and take some pictures of where the old gaskets are positioned and their orientation. Picture links to Amazon.com.

About the Author

John Cunningham is a Red Seal Qualified automotive technician with over twenty-five years of experience working on all types of equipment, grass machinery, ATVs, Dirt bikes, cars, and trucks. When not writing how-to articles, he may be found in his happy place – Restoring classic machinery.

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