The best flush mount gas cap depends on the tank and filler opening: the V-Factor 80024 is a weld-in option for motorcycle fuel systems, while the POSENG pop-up cap is designed for certain Harley-Davidson tanks. For a six-bolt fuel cell, choose between the black or silver PQY cap after checking measurements. The Boltigen deck filler is a marine option for a 1.5-inch hose, not a direct motorcycle replacement.
| Product | Best For | Key Check |
|---|---|---|
| V-Factor 80024 | Weld-in motorcycle applications | Hole and cap dimensions |
| POSENG Pop-Up Cap | Listed Harley-Davidson fitments | Model exclusions and thread |
| PQY Black Six-Bolt Cap | Black-finish fuel cells | Six-bolt pattern and venting |
| PQY Silver Six-Bolt Cap | Silver-finish fuel cells | Six-bolt pattern and venting |
| Boltigen Deck Filler | Marine fill hose setups | 1.5-inch hose diameter |
V-Factor 80024 Weld-In Gas Cap Kit
The V-Factor 80024 is a flush-mount gas cap kit intended for weld-in use on motorcycle fuel systems. Its listed configuration includes a weld-in bung for a 1-13/16-inch hole, a 1-5/8-inch outside-diameter knurled cap, and a seal.
Best for: Builders working with a tank designed for a welded-in filler. It is selected for its specific weld-in format and stated dimensions, which help buyers compare the cap with a prepared opening before installation.
Limitation: This is not described as a simple screw-in replacement. Confirm the opening and installation requirements before choosing it; weld-in work may require appropriate fabrication skills.
POSENG Vented Harley Pop-Up Gas Cap
This POSENG cap uses a push-and-turn design: press the center and rotate it 90 degrees to reveal or hide the inner cap. The listing describes billet aluminum construction, a vented design, and included O-rings. It is intended for specified Harley-Davidson models with a regular-thread or single screw-in cap.
Best for: Owners whose motorcycle matches the stated fitment and who want a low-profile pop-up style. The O-rings are listed as a feature for helping prevent leaks.
Limitation: Fitment is restricted. The listing excludes several models, including Sportster 2008 and newer, Sportster 48 2020, and bikes with double fuel tanks. Verify the exact model and tank before ordering.
PQY Black Six-Bolt Fuel Cell Cap
This black PQY cap is a non-vented, screw-down fuel cell cap made from CNC-machined AL6061-T6 billet aluminum. The listing specifies a six-bolt mounting pattern with 2.5-inch hole spacing and a 35.5 mm opening. It is presented for building a fuel cell or replacing a missing or damaged cap.
Best for: Fuel-cell projects or replacements that match the stated six-bolt pattern and opening. Choose this finish if black is preferred and the tank configuration calls for a non-vented cap.
Limitation: It is not described as a universal fit for every tank. Check bolt spacing, opening size, and venting requirements before purchase.
PQY Silver Six-Bolt Fuel Cell Cap
The silver PQY version shares the listed specifications of the black model: non-vented design, billet aluminum construction, six-bolt mounting, 2.5-inch bolt spacing, and a 35.5 mm opening. Its screw-down cap is intended for fuel-cell use or replacement of a compatible cap.
Best for: Buyers who need the PQY six-bolt configuration but prefer a silver finish. It is selected as a finish alternative rather than a different mounting design.
Limitation: The non-vented design and specified dimensions may not suit a tank with different requirements. Match the cap to the tank rather than relying on appearance alone.
Boltigen 1.5-Inch Marine Deck Filler
The Boltigen is a stainless steel boat fuel deck filler with a keyless cap and mirror-polished head. It is sized for a 1.5-inch inside-diameter fill hose and includes a retaining chain to help keep the cap from being misplaced. The listing describes the material as corrosion-resistant for marine environments.
Best for: Boat or marine installations using the specified hose size and a deck-fill arrangement. Its keyless cap and retaining chain are useful features for this marine application.
Limitation: This is a deck filler, not a motorcycle flush-mount gas cap or a six-bolt fuel-cell cap. Do not choose it unless the intended setup and hose size match.
Buying Guide: How to Choose a Flush Mount Gas Cap
What type of tank are you fitting?
Start by identifying whether the cap is for a motorcycle tank, a fabricated fuel cell, or a boat deck fill. These products use different mounting methods. The V-Factor kit is for weld-in use, the POSENG cap is described for specific motorcycle fitments, the PQY caps use six bolts, and the Boltigen filler connects to a marine fill hose.
Which measurements should you check?
Compare the tank opening, cap diameter, hole spacing, and hose diameter with the listed specifications. For the V-Factor kit, check its 1-13/16-inch hole and 1-5/8-inch cap measurements. For the PQY models, verify the 2.5-inch bolt spacing and 35.5 mm opening. For Boltigen, confirm a 1.5-inch inside-diameter hose.
Do you need a vented or non-vented cap?
Check the fuel system’s requirements before selecting a cap. POSENG describes its motorcycle cap as vented, while both PQY fuel-cell caps are labeled non-vented. The available product details do not establish that one type suits every tank, so match the cap to the tank design.
Should you choose a pop-up, screw-down, or keyless cap?
A pop-up design can provide a low-profile appearance when closed; a screw-down cap is the listed style for the PQY fuel-cell options. Boltigen uses a keyless marine cap. Choose based on the intended application and how the cap mounts, not on closure style alone.
Frequently Asked Questions
Is every flush mount gas cap universal?
No. The listed caps have different fitments, measurements, and mounting methods. Check the product dimensions against the tank before buying.
Can the V-Factor 80024 be installed without welding?
It is listed as a weld-in kit. The product details do not describe it as a screw-in, no-weld replacement.
Are the PQY black and silver caps different in fit?
The supplied feature details list the same mounting and size specifications for both. The stated difference is the finish color.
Does the Boltigen deck filler fit a motorcycle tank?
It is described as a marine deck filler for a 1.5-inch fill hose, not as a motorcycle tank cap.
What should Harley owners verify before choosing the POSENG cap?
Confirm the exact model, tank, and thread style, and review the listing’s exclusions. It is not described as fitting every Harley-Davidson model.