Valve adjustment

Valve timing is important to how your mower runs. This video walks you through the whole process step by step, including: Setting the engine to TDC (Top Dead Center) checking lash (Gap) and adjusting valves.

Over View

You’ll find useful resources on this page, tips, links to tools, parts and supplies required to complete your repair.

As an engine wears the critical tolerances between the rockers and valve tips usually increases and this causes a few problems. They include: hard starting; stiff pull cord; engine oil leaks; lack of power; erratic idle; noisy engine.

The gap (lash) between the rocker and valve tip is adjustable and this video covers that process step by step.

Before working on your mower be sure to remove the plug wire to prevent accidental starting, see “Repair Safety Video”.

Tools & Parts

To nail this procedure you may need the following tools, parts and supplies.


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 type of fastener sizes. Set includes spark plug sockets. Picture links to Amazon.com


Feeler gauge

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

WD40

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

Drill/Screw Gun

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 driven 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

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Auto Technician and Writer at | Website

John Cunningham is an Automotive Technician and writer on Lawnmowerfixed.com. I've been a mechanic for over twenty years, I use my knowledge and experience to write "How to" articles that help fellow gear-heads with all aspects of mechanical repairs, from lawn mowers to classic cars.