Generac QT 3.9L 40kW — Spark Plugs - Inspect and Set Gap
Maintenance
For the Generac QT 3.9L 40kW, from the Generac owner's manual.
Applies to: Generac QT 3.9L 40kW, Generac QT Series, Generac V-type engine
Before you start
- Do not blast the spark plugs to clean.
Parts for this job
- RC12LC4 Spark plug — Generac QT 3.9L 40kW Amazon eBay $26.61
Part numbers from the service-parts lists for Generac QT 3.9L 40kW, Generac QT Series. Verify against your serial number before ordering; some links are affiliate links.
Procedure
- Clean area around base of spark plugs to keep dirt out.
- Remove spark plugs and check condition; replace if worn or reuse questionable.
- Check gap with a wire feeler gauge; adjust by carefully bending ground electrode.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Spark plug gap 1.01 mm (0.040 inch)
Full service-parts list: Generac QT 3.9L 40kW →, Generac QT Series →
Source: Generac owner's manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.