When you're customizing your cafe racer, scrambler, brat, or bobber, changing the headlight can drastically alter the bike's look and functionality. However, before you can select the right headlight mounting brackets, you must determine your fork tube diameter. Let's dive into this essential step to ensure a seamless headlight swap.

Identifying the correct fork diameter is crucial for selecting the appropriate headlight mounting brackets. This measurement ensures that your new headlight will fit securely and align perfectly with your front wheel, enhancing both the aesthetics and functionality of your custom build.

To find your fork diameter, you'll need a Vernier Caliper or ruler. The ruler is far less accurate. Measure the diameter of the fork tubes where the brackets will be mounted. This measurement is typically taken at the top of the fork tube, just below the top triple tree.

Or, Use the list we have laid out below to identify your fork outer diameter.

(Just a note, we've tried to make this as accurate as possible.) However, common fork diameters for custom builds range from 32mm to 58mm, but it's best to measure your own forks to be 100% certain.

Once you have your fork diameter, you can choose headlight mounting brackets that match. Many manufacturers provide compatibility information, making it easier to find the right brackets for your bike.

Motorcycle Fork Diameter Reference

Bike Make Year Model Fork Diameter (mm)
Aprilia RS126 RS125 50-54
Aprilia 1995 - 1998 RS250 50-56
Aprilia 1998 - 2003 RS250 50-55
Aprilia 1997-2004 RSV Mille 53-55
Aprilia 2005 RSV Mille 53-55
Aprilia 1998 - 2004 RSV-R Mille 51-58
BMW 2014-Present R nineT 55
BMW 2017-Present R nineT Scrambler 55
BMW 1970-1996 R series (Airhead models preferred) 35-39
BSA 1957-1963 Gold Star 35
BSA 1958-1970 Spitfire 35
Ducati 620DS Multistrada 50-
Ducati 1998-2004 750SS 50-
Ducati 848 848 53-55
Ducati 2001- S4 900 Monster 50-
Ducati 1997- ST2 1997 50-
Ducati 999 999 53-55
Harley 1986 Late - 1987 883 & 1200 Standard, 883 Deluxe, 883 Hugger 35
Harley 1954 Onward Big Twins 41
Harley Pre 1970 Sportster 35.5
Harley 1970 - 1986 Sportster 35.5
Harley 2004 - 2018 Sportster 39
Honda 1972-1983 CB350F 35
Honda 1975-1981 CB400F 35
Honda 1978-1983 CB500/550 35
Honda 1973-1982 CB650 37
Honda 1969-1978 CB750 37
Honda 1978-1982 CX500 35
Honda CBR250R MC20 37
Honda CBR250RR MC23 37
Honda NSR250R MC18 MC21 MC29 41
Honda CB-1 401 41
Honda NC31 VFR400 NC31 41
Honda NC36 RVF400 NC36 50-54
Honda 2003-2005 CBR600RR 54
Honda 2005-2007 CBR600RR 48-55
Honda 2008 CBR600RR 48-56
Honda 1992-1998 CBR900RR 45
Honda 1998-2000 CBR900RR 45
Honda 2000-2001 (929) CBR900RR 43
Honda 2002-2004 CBR900RR 53-55
Honda 2004-2008 CBR1000RR 53-55
Honda 2009 CBR1000RR 53-55
Kawasaki 1998-2020 W650 39
Kawasaki 2000-2016 W800 43
Kawasaki 2003-Present Z900 42 (varies slightly by year)
Kawasaki ZZR251 37
Kawasaki ZXR250A 50-53
Kawasaki ZXR400-H 50-52
Kawasaki 1991-2000 ZXR400-L 53-55
Kawasaki 2003-2005 ZX6R 50-
Kawasaki 2005-2007 ZX6R 50-54
Kawasaki 2007-2009 ZX6R 40 Cr
Kawasaki 1996-2004 ZX7R ?
Kawasaki 2004-2006 ZX10R 50-56
Kawasaki 2006-2008 ZX10R 50-?
MV Agusta F3 675 & 801 50-56
MV Agusta F5 ?
Royal Enfield 2013-Present Continental GT 41
Royal Enfield 2017-2022 Himalayan 41
Royal Enfield 2022-Present Himalayan 54
Royal Enfield 2018-Present Interceptor INT650 41
Suzuki RGV250 VJ22 ?
Suzuki 1991-1996 RGV250 VJ22 50-54
Suzuki 1990-1996 GSX-R400 GK76 50-54
Suzuki 2004-2006 GSX-R600 50-56
Suzuki 2006-2010 GSX-R600 50-55
Suzuki 2010-2016 GSX-R600 40 Cr
Suzuki 2006-2008 GSX-R750 50-55
Suzuki 2001-2003 GSX-R1000 50-56
Suzuki 2003-2005 GSX-R1000 50-56
Suzuki 2005-2007 GSX-R1000 50-?
Suzuki 2008 GSX-R1000 50-?
Suzuki 1998 TL 1000S 50-57
Suzuki 2004 SV 1000S 46-48
Suzuki 1989-1991 GSX-R1100 43-44
Suzuki 1991-1993 GSX-R1100 52-?
Suzuki 1993-1995 GSX-R1100 52-?
Suzuki 1999-2008 GSX-1300R Hayabusa 50-57
Suzuki 2009 GSX-1300R Hayabusa 50-57
Suzuki Boulevard series 37-41 (varies by year and model)
Suzuki 1976-1983 GS series (GS400, GS550, etc.) 35-38
Suzuki 1985-2009 Intruder series 37-41 (varies by year and model)
Suzuki 2003-2016 SV650 41
Triumph 2001-2017 America 41-43 (varies by year and model)
Triumph 1959-1982 (Classic models preferred) Bonneville 35-38
Triumph 2000-Present Bonneville 41
Triumph 2000-Present Thruxton 41 USD
Triumph 2006-2008 676 54 USD
Triumph 2009-2011 676 41
Triumph 2011-2013 675R 43
Triumph 2013-2017 675R 54 USD
Triumph 2013-2017 675R 54 USD
Yamaha FZR250R 3LN 38
Yamaha FZR400RR 3TJ2 43
Yamaha FZR600 3HE 38
Yamaha FZR600R 4JH 41
Yamaha 2009-2018 FZ6R 40 Cr
Yamaha 1999-2003 YZF-R6 600 43
Yamaha 2003-2005 YZF-R6 600 43
Yamaha 2006-2008 YZF-R6 600 50-56
Yamaha 2008-2016 YZF-R6 600 40 Cr
Yamaha 1993-1996 YZF750R 50-58
Yamaha 1996-2001 TRX850 41
Yamaha 1996 YZF-1000 48
Yamaha 1998-2002 YZF-R1 (4XV & 5JJ) 50-56
Yamaha 2002-2004 YZF-R1 (5PW) 50-56
Yamaha 2004-2007 YZF-R1 (5VY) 50-56
Yamaha RD series (RD350, RD400) 35
Yamaha 2000-2015 Road Star series 41-43 (varies by year and model)
Yamaha 1996-2014 Royal Star series 38-41 (varies by year and model)
Yamaha 1978-1999 SR400 38
Yamaha 1978-1999 SR500 38
Yamaha 1970-1983 XS650 35
Yamaha 1976-1981 XS750 38
Yamaha 1984-2009 XV series (Virago) 35-41 (varies by year and model)
Yamaha 2016-Present XSR series (XSR700, XSR900) 52
Yamaha 1976-1989 XT500 38

Selecting the correct headlight mounting brackets based on your fork diameter is a crucial step in customizing your bike's front end. It ensures that your new headlight is securely mounted, providing a clean, professional appearance that complements your custom build.

There are a few other companies that have fantastic tools for identifying fork Diameter, check out ALL BALLS for their bearing identifier for your front end conversion.

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