Topic: I hate brake fluid! / caliper "life hacks"--dual disk on a 400/500/550 four

[spuds]

I am SOOOOO close to having this 400F project done!!   I REALLY don't want to start all over with my front brakes.    I've got some undesirable symptoms, and I'm hoping to discover that perhaps they are somewhat related (d'uh of course they will be related!), BUT more so that there's maybe a magic trick of some kind to deal with what might be "root problems" to totally avoid disassembly (did I mention I HATE working with brake fluid?).

Big rocks:  400F, with a CB500F front end, set up to run dual disks.     Build:  http://forums.sohc4.net/index.php/topic,168844.0.html

I know that there's much discussion on the "yes it works/ no it doesn't work" mating of the 400F's 14mm master cylinder and a pair of single 38mm piston calipers.   I've read so much on this, that I am utterly confused (and it doesn't take much!!) ---so had decided that initially I'd try my 400F OEM master cylinder.

Symptoms:

Brake lever "feel"/function:
After at least 1.5 hours of bleeding (including drawing in the lever, holding momentarily and then releasing it (flicking it); and the overnight clamping of the brake lever, gently tapping the whole system with a hammer), there's still lots of travel in the brake lever (The firmness that I expect comes about 1" from the handgrip).   
Related to this (?), the brake light only illuminates when the lever is about 1" from the handgrip.   I know the lever will never feel like a CBR600RR, but I know there's room for some improvement here.....I'd hope that firmness would happen about 3/8 to halfway into the lever's travel.

Caliper function:
When applying the brake lever,
LHS piston/outer pad that moves toward the rotor (yeah) BUT sticks ---it doesn't return on its own.
RHS piston/outer pad doesn't move at all.

The set up:   

CB400F master cylinder (not disassembled and rebuilt-----full disclosure).   This master cylinder though was used on several occassions to push pads/pistons out of calipers. (for whatever that's worth).

Brand new SS line down to the OEM splitter, then a double banjo bolt and two brand new SS lines down to each caliper.
OEM CB500/CB550/CB400F calipers----cleaned....yes....I couldn't see (with an UNTRAINED eye) anything in them that looked like it would impede function; brand new bleeder screws, brand new seals, brand new phenolic (spelling?) pistons, brand new EBC pads.

I've got the forks in reversed---so that the calipers ride behind the forks.  I know that this will make bleeding more time consuming/challenging as the bleed screw is no longer the highest point on the caliper, but figured (at the time) and accepted that bleeding the system would take longer.     

The assembly: caliper bores looked clean.   I gave each of them though a quick rub with some 1500 (ish...can't recall exactly, but it wasn't 80 grit!) sandpaper.   Gave the pistons and outer pad edges a quick rub with the sandpaper too.    Smeared the lightest of coatings of di-electric grease (mechanic buddy suggested this, and I'd also read in other posts about using caliper assembly lube ----but try to find a product called caliper assembly lube....elusive) on the pistons and pads surfaces.
One piston seemed to "click" in real nice....   Not sure if that what it was supposed to feel like, but but it literally had a soft "click" to it just before bottoming.
The other piston...not so much----took a little more force to go in, and there was no discernable "click".   (I bet I know which caliper (see above) that one is!)
Pads---both were sanded a little...one can wiggle around a TINY bit when it's sitting there against the piston, the other is tighter. 

Everything was buttoned up on the bike.  I did NOT make a note of which assembled caliper went on which side....

Brand new DOT4 was pushed into the throttle side's caliper bleed screw with a syringe, and I left the LHS caliper bleed screw open a bit and had fluid come out there. Tightened that screw up, and continued syringing fluid in (eventually) both calipers.  Eventually fluid reached the master cylinder reservoir.  And the bleeding process began.

The questions now:
On "bleeding".   With the reservoir cover off....when the brake lever is initially squeezed there is usually a little bit of fluid that pops up----is that really air coming out?  Or is it just fluid that's popping up due to the lever being squeezed?   Trying to discern if there's still a TON of ait in the system (really shouldn't be though right---due to the fluid having been pushed into the calipers from below???)

The bigger question----
Do I need to start over?  Push the pads/pistons back out......do MORE cleaning?  More sanding?   
Do I need to use a different master cylinder?      Which one?   Some say a smaller piston, some say larger....I'm confused!!
Or do I patiently just keep bleeding, and bleeding....and bits will start working as they should?    If I was told "keep bleeding"---I would happily persist (anything to avoid taking everything apart again!!).
 
thanks in advance.....

[DaveBarbier]

On the subway and didn’t read the whole thing, but the calipers being reversed and trying to bleed with the bleeder not at the highest point won’t just take “longer” to bleed...since air floats it won’t bleed properly at all. You can remove one caliper bolt, swing the caliper level (put a piece of wood between the pads if you need) and then bleed normally.

Maybe you revisit this later on in your novel but I’ll read it later. I just saw something that might be an issue and wanted to flag it. 

[DaveBarbier]

Read a little more.

Why did you “sand” the edges of the phenolic piston?? It should be smooth, don’t sand the pistons at all.

Second, don’t use dielectric grease on the pistons. You have to use brake fluid or brake assembly lube. Your buddy is wrong to use that. Let us know where he works so we don’t go to his garage. If I were you I’d disassemble, flush and start over. Grease like that reacts with the brake fluid and worst case it degrades the fluid. It also might be because of the grease that the piston isn’t returning when the release the lever. The brake piston seal needs “grip” on the piston to help retract it. If it’s greasy, it can’t grip it. I really suggest you read the post by TwoTired about which products to use to rebuild the system.

Third, the pads should pretty much drop in the caliper bore. Sand, grind or file down the paint that comes on them so they go in smooth. The pads can take high vacuum lithium grease on the pad back and sides of the metal (not on the pad material at all!)

[DaveBarbier]

This is the link I was thinking of. Read and do this.

http://forums.sohc4.net/index.php/topic,104349.msg1215995.html#msg1215995

[flatlander]

dave's link is good. for starters, do as it says there and then check again. 
then, after careful bleeding, if you still don't like your lever travel - a larger MC moves more fluid, i.e. travel decreases and so does feel. so it's a compromise. if i remember correctly i have a 16mm with dual discs which works fine for me.

[spuds]

K.   

Thanks folks.

I had slowly been ramping myself up to disassemble and start over, but just wanted to check to see if there were some short cuts or tricks that might have been suggested.

Thanks for the suggestions on using some brake fluid on the pistons, (and not grease), and the clarifying point (to me anyway) that the pads need to pretty much just drop into the bores.   

And for the hint to help with the bleeding (rotating the outer part of the caliper to raise the bleed screw)!!

Cheers,

[seanbarney41]

dave's link is good. for starters, do as it says there and then check again. 
then, after careful bleeding, if you still don't like your lever travel - a larger MC moves more fluid, i.e. travel decreases and so does feel. so it's a compromise. if i remember correctly i have a 16mm with dual discs which works fine for me.

+1, I have never been a fan of the stock master on these bikes, even with just one caliper.  So, unless you are in love with the stock looks, anything from the 80's on up is a huge improvement and I also use a 16mm (from a Suzuki Bandit)  Lots of affordable options on Ebay in many shapes and sizes...