Triumph 21-1883 Fuel Tank Front Mounting Stud
Part 21-1883 (factory S1883) is the shouldered stud that holds the front of the fuel tank on the frame of late pre-oil-in-frame Triumph unit twins. In 1969 Triumph replaced the earlier front mounting bolt (82-1808, used 1966–68) with this stud and a separate nut. The tank sits on rubber mounts and cups, which isolate it from engine vibration. If you’re refitting a tank after paint, replacing a stripped or bent stud, or rebuilding the whole tank mount, this is the correct part for the job.
Specifications
- Part number: 21-1883 / Factory / alternate number: S1883
- Type: Shouldered stud, fuel tank front mounting
- Thread: 5/16″-24 UNF
- Overall length: about 1-9/16″ (39.7 mm)
- Quantity required 2 per tank (left and right front mounts)
- Mates with Nut 14-1302, cup 82-3814, rubbers 82-5228 and 82-5229
- Replaces Front mounting bolt 82-1808 on 1969-on models
- Material / finish: zinc-plated steel
- Country of manufacture: UK
Fitment
- Triumph T120 / T120R Bonneville 650 1969–1970 Pre-oil-in-frame
- Triumph TR6 / TR6R / TR6C Trophy 650 1969–1970 Pre-oil-in-frame
- Triumph T100 / T100R / T100C / T100S 500 unit twins 1969-on Through the end of 500cc twin production
- Not for: 1966–1968 models, which use the bolt 82-1808, or 1971-on oil-in-frame 650/750 twins, which use a different tank mounting system (kit 00-0105). If your bike has a non-original or aftermarket tank, check the thread in the tank’s front boss before ordering.
Installation Tips
- Clean the threads in the tank’s front mounting bosses before fitting, and chase them with a 5/16″-24 UNF tap if they’re damaged or full of paint.
- Assemble the rubbers and cups in the factory order so the tank stays rubber-isolated. Metal-to-metal contact passes vibration into the tank and can crack seams.
- Snug the nuts so the rubbers are lightly compressed. Overtightening defeats the isolation and can strip the threads in the tank.
- Replace hardened, cracked, or collapsed mounting rubbers at the same time. They’re inexpensive and protect a costly tank.
Complete the Tank Mount
- Fuel tank front mounting nut 14-1302
- Tank mounting cup 82-3814
- Tank mounting rubbers 82-5228 and 82-5229
- Rear tank mounting bolt 82-7388 and rear rubber 82-5336
- Full Kit TBS-0091 A
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Frequently Asked Questions
What does Triumph part 21-1883 fit?
It’s the front fuel tank mounting stud for 1969–1970 Triumph T120 Bonneville and TR6 Trophy 650s, and for 1969-on Triumph T100-series 500cc unit twins. Two are used per tank.
What is the thread size of the 21-1883 tank stud?
5/16″-24 UNF.
How long is the 21-1883 stud?
About 1-9/16″ (39.7 mm) overall.
Is 21-1883 the same as S1883?
Yes. S1883 is the number in Triumph’s factory parts books, and 21-1883 is the common service and aftermarket form of the same part.
My 1968 T120 has bolts at the front of the tank. Do I need this stud?
No. 1966–1968 models use the front mounting bolt 82-1808. The stud-and-nut arrangement started in 1969.
Does this fit oil-in-frame 1971-on Triumph 650 and 750 twins?
No. Oil-in-frame models use a different tank mounting system.
How many do I need?
Two, one for each front mount.
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