Triumph Repair: brake master cylinder, cylinder hones, brake master cylinder

Question
QUESTION: Hi Howard, I have a 1972 spitfire I had a problem with the brake master cylinder leaking like crazy out the end of the plunger and on to my feet. I bought a rebuilt kits from Victoria British. and rebuilt the brake master, clutch master, and Slave. Everything has been well for about six weeks and now the brake master cylinder has now started leaking again. Not as much as before but I have to add weekly. Its coming out the plunger again. Can a brake master just go bad? Even if you rebuild it will never be the same as new? Or is there a better rebuild kit out there or can you think of anything that I might want to check out when I take it apart again? thanks Mark

ANSWER: Hi Mark,
Rebuilding a master cylinder requires more than just putting a new kit in.
The bore must be honed and then examined for pits with a strong light. It sounds like you have pits in the bore or you damaged a seal installing it or you used DOT 3 brake fluid in which case you may have damaged all of the seals in the whole brake system and maybe even all the flex hoses. Also the clutch system.
If you used DOT 3 flush the clutch and brake system completely with DOT 4 fluid and put another kit in the brake master (after examining for pits)
Let me know.
Howard

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QUESTION: Thanks Howard I did use Castrol LMA forgot to mention that.. So hone it makes sense where can I get such a small hone for this project? thanks Mark

Answer
Most any auto parts store have brake cylinder hones and any tool trucks that visit shops. Rotate the hone at a slow speed and move it in and out as you use it so as not to cause groves in the bore and use a fluid like diesel fuel or WD-40 or kerosene to lube the hone as you use it. If you can't get all of the pitting out you will need to either replace the cylinder or have it sleeved.
Howard