I replaced a leaking master cylinder on my ‘84 R65LS. The easy two finger pull is gone. Not knowing any better I just ordered my replacement from the parts fiche and now need a solid four finger pull. The new cylinder is a 15mm and I’ve since discovered that some LS’s used a 12mm and some a 15mm. Of course the 12mm is no longer available. I can’t believe I would have done this but I apparently threw my old one away. My assumption is that it was a 12. First, would a 15mm master that’s mismatched to the calipers account for the hard pull? Second, are my only choices replacing the calipers to match the 15mm master or finding a rebuilt 12mm?
Yes if you replaced a 12 MM master with 15 MM master then the pull will be substantially harder. EME has 12MM in stock. Probably other people as well. Be sure that it fits you bike. I am not your parts guy. 🙂 It might be possible to change out just the master cylinder and not the whole hand grip https://www.euromotoelectrics.com/product-p/brakeassembly367.htm
You'd also do better to replace the OEM rubber brake hoses with modern "stainless steel" brake hoses, while the brake system is apart. See....
https://www.airheads.org/community/parts-is-parts/brake-hose-failure-causes-cures/#post-6217
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
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