79 F front brakes

[2manybikes]

The front brakes on my stock 79 F are not going to get it. I am loathe to change the front master cylinder to something else, I would like to feel I have exhausted all possible alternatives. The master cylinder has been rebuilt, as have the calipers, even with an upgrade to SS pistons. I have a friend with a Norton, who had the front master cylinder bored and re-sleeved, thus increasing the bore. Anyone ever tried this? Also, anyone who has changed theirs out, what did you use, and how do you feel about the difference? Thanks!

[jetmechmarty]

A larger bore in your master cylinder will make the brakes feel much worse, not better. For a more linear, less wooden feel, you need a smaller bore.



For professional help, contact Michael Mercury Morse at vintagebrake.com He's the best.

[bikerphil]

For a Standard with SS lines, a 14MM bore aftermarket MC is the ticket.

[2manybikes]

79 F front brakes

Thanks for the info! Brakes as of late, seem to be the bane of my existence. One of my 4 wheeled "toys" is being a PITA now as well. I will check into your suggestion.

[HalfCentury]

Are you using the OEM 35+ year old brake line?

[IanDMacDonald]

Half Century and Phil are leading you in the right direction. I followed Phil's advice and went with SS lines and a 14mm MC. I then went to Blue Spot calipers, which is too much braking for the bike. So, when ur used to old crappy brakes, and goto Blue Spots, watch out!

Then again, I have six-pot Brembos on my Triumph, and those are PHENOMENAL!

[HalfCentury]

The date of manufacture should be stamped on the brake line if it is the OEM. The OEM rubber line was intended to be replaced at 4-5 yrs of age. 40 years later, they are a disaster waiting to happen.

Unlike the intake manifold boots which can be cracked on the outside yet leak-proof, the brake line can look fine on the outside yet be failing on the inside.

The intake boots are subject to high-velocity low-pressure fluid flow. The brake line is the inverse; low-velocity high-pressure. The rubber brake line can burst just when you want the bike to stop.

[2manybikes]

Brakes

Thanks for the additional info. I can almost see something printed at the top of the line, but I'm going to have to find my magnifying glass to make it out. The brake lines were replaced during the restoration with NOS, or OEM parts. I can't remember. I will however, look into it. Especially since I now now about the date code.

[HalfCentury]

I just removed the mid,rear and front left lines from my 82 JX1100 this past week. The date code is 12/81; about 30 years past its expiration date. Reading the date code for me requires a very strong magnifying glass and a bright light. The date code fades with age.

On the XJ, the front master cylinder only controls the front right caliper. The line is completely exposed and easy to replace without any complicated disassembly of the bike. I replaced that line last year with a stainless steel line and the difference from the OEM is amazing. The front lever now feels like total control of the front braking.

The complete ss brake line set is kind of spendy, but I consider it to be the most important investment in personal safety.

[DiverRay]

I put the SS lines on an F about 10 years ago. I did NOT change the size of the MC, and the brakes felt a little "wooden", not a lot of feel. I've done the same thing to a different '79, but went to the 14mm and it was GREAT! Stopped well, and easy to regulate. One thing I did was rebuild ALL the components, and went to DOT5 fluid, as it does NOT attract water. I had the '79 parked for about 7 years because of the engine, and the brakes didn't lock up, and still worked! With these bikes, the brakes are stuck after about 2 years of not moving, around here, that's six months to one year.