I've had a look round for a used Gen 2 Street Twin master cylinder to upgrade my current 11mm mc to 12.7mm. They're pretty thin on the ground. However there are a couple of master cylinders from the Thruxton 1200 RS (part number T2025933). Would anyone happen know the bore of that mc?
Check, but I am pretty certain any of the Brembo caliper equiped gen2 900 LC master cylinders would be 12.7mm. The Thruxston, being twin disc is likely to be 14mm but please check. I have not tried a 14mm myself (on a 3 pot caliper) but I have read testimony (from this forum or Triumph Rat) from someone who has. This gent says it works. So for being vague but I hope this helps.
I've just come across some Street Twin parts from a 2019 model, which includes the Brembo 4-pot caliper and front master cylinder. So I'm hoping I'm safe in assuming the master cylinder is 12.7mm. As ST Rat says, it seems logical to fit the bigger mc with a 4-pot, so I'm going to take a chance.
