front f4i fork/brake swap = rear f4i brake cylinder?

[dozyproductions 51]

Really quick question. A lot of the f4i fork swap threads mention buying something similar to a f4i rear cylinder along with a f4i front M/C. Could some one explain to me exactly why? I have a suspension shop doing this job for me and the mechanic didn't want to keep the rear f4i cylinder because I couldn't give him a good enough reason to why. Any help? Thank you. 

[Captain 80s 164]

I think it has to do with the diameter of the original not working great after de-link. 

[TheLimey 30]

You'll be operating all three of the rear caliper pistons with the rear master cylinder rather than just the outer two. The middle was previously operated by the secondary master cylinder on the front left caliper, but now you're going to link all three rear pistons together. 

[mello dude 473]

For a delink job and going to different front forks, .. for the rear you do need to change out the master cylinder to a 14mm diameter. Options.. F4i, VTR1000, RC51, CBR600RR. All use the same base castings. - I just bought a '02 RC51 m/c new, I didnt want to have to rebuild. --- The rear caliper pistons need to be working together. I used a bridge line that works fine, and one OEM brake line from the m/c to the caliper, I think I still have pictures in my gallery. - Other guys have just used 2 OEM lines to the caliper and then even others have just drilled out a path in the caliper so just one line is needed, and then one hydraulic port is sealed. 

All work fine. 

Please dont forget this step, your rear brake will be crap if you dont. 

Photos -- I have been running this setup a long time now, and it still works well.

 

 

Cheers 

[dozyproductions 51]

Thank you guys! This was the last link 'we' needed! Gathering the parts, itself, has been a challenge being that so many of the used 'good' looking parts have had their own individual problems. The rear cylinder, that was already bought, doesn't seem to be an exception.