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Discussion Starter #1
ok, riding in the MD country side yesterday after work with my green eyed brunette, a lovely evening for a ride, and i'm just sick of that sh!t front brake on the CB 650. i've got new nice brake pads that improved a bit, but still, i need more. is there ANY thing i can do to avoid swapping the whole front with a goldwing's two rotors? any other disk/rotor/master cylinder swap i could do?

i was even thinking about maybe calling these dudes and seeing if they'd do this to my 19: http://www.cookcustomchoppers.com/parts.htm

CB650, FauxCatiFT500
 

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if you have one of the comstar 650s, you should consider swapping the front end with a cb750F dual disc front end. I don't think the GL1000 swap works for 650s, just the 750. I am not 100% sure but you might be able to use the DOHC cb750F 1982 twin piston calipers if the 650 forks are the same as the 750s (this only applies to comstar bikes).

Off the top of my head a set of stainless lines and ebc brake pads are a good improvement. Next I would consider a modern sport bike master cylinder with the same size piston you have now. I find tha tthe modern m/cs have better feel through the lever pull than these old m/cs because of lever and pivot angle.
 

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Discussion Starter #3
i've got the EBC's on (or maybe some SBS, i can't remember which ones i chose) and my wheels are spokes. what about a master cyl with a larger piston?

picture (don't mind the welder):



CB650, FauxCatiFT500



Edited by - jb on Oct 17 2007 2:43:02 PM
 

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I have heard of guys using the cbr 600 f2/f3 cbr929 master cylinder with the single disc but it is kind of overkill because it kills the brake feel.

Others have more expirence with master cylinder piston size (DiamondJ??) than I do and can weigh in on the effects of a larger piston (you can also do a search since we have covered this a lot before), but from my understanding with a single brake you want a smaller piston so as to create more line pressure.
 

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I don't remember the CB650 brake being that bad. Of course a double disk setup would be better, but you should be able to make what you have work good enough. Is your brake fluid fresh? Is the caliper and the all the parts that slide clean and free to move? Is the master cylinder in good shape? Braided steel lines will help. Finally, is the disk glazed? it can get really glazed to the point it needs to be mechanically cleaned. We used to chuck them up in a lathe and hit them with a body grinder while the were spinning. It gave a nice kind of satin finish that worked well. I would also consider sanding it with a orbital sander to break the glaze.

AHRMA 412
Vintage racing - old guys on old bikes
 

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A larger piston on the m/c for the same size caliper will give you a light switch on/off brake. Basically you will be moving too much fluid into the same size caliper.

A braided line is one of the best improvements you can make if you are keeping the stock caliper and m/c. Ken's suggestions are excellent - go through your brake system and make sure everything is functioning as it should be. Deglaze the rotor. Remember that regular Dot 3/4 brake fluid is hygroscopic and absorbs water over time causing corrosion. Cleaning and rebuilding the m/c and caliper along with fresh synthetic Dot 3/4 brake fluid will definitely help.

If you still hate the front brake, start looking at other single rotor set-ups off of more modern bikes - EX500, GS500, etc... Although then you get into having to make adaptors to mount the rotor, matching the rotor diameter to the caliper, etc... Maybe you can use a CB750 front wheel with one rotor removed? Geet? Any benefit in rotor size with this?

I've switched over to Brembo m/c's on a couple of bikes as they are much better performance-wise and the East Coast Brembo distributor is an ex-coworker. If this is something you are interested in, contact Fred at:

www.yoyodyneti.com

but you'll need to be able to tell him the current m/c piston diameter so he can match it up. Also make sure he knows you want a mirror mount and a brake light switch on the m/c along with the brake lever color (silver or black).....

Jim
 

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Discussion Starter #8
MD=drought, no water in fluid. fresh synth fluid from july. caliper rebuilt in feb/march, everything is clean and works well. the rotor doesn't seem that glazed really, but i'll hit it with an orbital sander. it's just that this thing doesn't have enough bite. a dude i know had a 650custom and said that it's the steel honda rotor typical feel. he knows a guy in the N.W. that'd drill them correctly for about $75 i think. still though, when i try to brake hard i get that spongy feel. the handle seems nice and tight but it's the rotor/caliper that seems to be soft on bite.

i'll sand the rotor either today or tomorrow and see how it feels, then, i'll move on from there to other mods/solutions.

thank you.

p.s. i'm just really pissed off at this thing because my FT500 has so much better f'n bite that i feel the bigger/heavier bike should be the one with the fat brakes.

CB650, FauxCatiFT500
 
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