A popular racing mod back in the day on pre-1970 Triumph 350, 500 and 650 unit twins was to allow the engine to breathe through the primary side case. Models from 1970 and on already featured this design but pre-1970 models did not.
If your engine features the timed inlet cam breather and you would like the engine to breathe through the primary you would have to drill (3) small holes near the bearing housing...
I won't get into detail regarding the mod as you can look it up online. This plug will thread into your engine case which will replace your filler / inspection plug and you can then run a breather hose on the stub. Thread pitch is 16TPI and can accept a 3/4" I.D. breather hose.
- Made in England
- OEM part number is 57-2166 and T2166
- Free shipping in the USA