Author Topic: CB400F - Brake Caliper Installation & Fuel Leak (Read 3310 times)

jakec · « **on:** March 17, 2018, 02:48:21 PM »

Hey guys,

As you may know I am working through a myriad of problems with my CB400F. I have not yet ridden it

Anyways I got the wheels back with the new tires, and installed them. Everything went smoothly there with the exception of the front brake caliper, which was engaged constantly when I reinstalled it. So I have drained all of the brake fluid and taken the caliper off to try and depress the piston. There is no fluid and the drain valve is open. I'm not sure if the piston is pushed in all the way, but when I installed the brake again it was rubbing the rotor and made it hard to roll the bike. This is with no fluid so the caliper is relaxed.

Problem #2, I decided to come back to the brake a little later and see if the bike would start since everything was ready to make another attempt. The good news is that it cranked over with electric start without blowing any fuses. However I noticed after about 5 seconds that there was fuel dumping out of the collective fuel nipple for the carb bank. So I immediately stopped.

I pulled the old line off and the filter that was on it was a little dirty so I tossed it as I have more to replace it. I rigged up a new line and filter and I found that it's nearly impossible to reach the nipple down in the middle of the bike (tank was off, of course). I also noticed that the nipple can swivel front to back, which made it really difficult to try and get a line on it. I had to give up on that because I was getting a little frustrated, so I'm taking a break at the moment. Is it normal for the fuel nipple to swing around freely like that? Or is it loose and that is why it's leaking? I had assumed that one of the connections, on either end of the old fuel filter was the source of the leak.

The swiveling nipple on my bike does not have a number in this fiche but it's easy to find in the center of the drawing.

jakec · « **Reply #1 on:** March 17, 2018, 05:51:56 PM »

Here are some photos of the brake caliper.

The piston looks like this. Should it be further in? I could probably push it in if I had a clamp, but I don't own one right now.

Here is what it looks like with the pad installed. it's tough to see but there is about 1/8" - 3/16" of pad sticking out. Is this the normal amount or should it be less?

If the piston is fully depressed then i'm at a loss as to how to fix this. It's like I need a spacer to gap the caliper halves off of the arm they bolt onto. If the piston should be further depressed, then I guess I can get a clamp and that will hopefully fix it.

ekpent · « **Reply #2 on:** March 17, 2018, 06:08:33 PM »

You will probably need to put fluid back in and then pump the master while keeping enough fluid in to eventually completely remove that piston. Then you will remove the rubber ring gasket inside the caliper and clean all of the crud,you will see a white build up in that that groove if it has not been cleaned in a long time. Also clean the piston and interior well and clean all the old crud off the outside edge of the brake pad if there is any. Also if your tiny return hole is plugged in the master cylinder the piston will not retract correctly. Collapsed break lines do the same. Do those though and it should be good to go for a long time.
As for the swiveling nipple that is how they are. Heating the very end of the fuel line with a heat gun will soften it and putting a little grease on/in it will make it go on easier but do not do it around gas fumes,be careful. Long nosed pliers can be helpful there also.

Stev-o · « **Reply #3 on:** March 17, 2018, 06:17:22 PM »

Eric gave you good advice, I would change the seal since you have it apart.

Getting fuel line on can be a challenge, I sometimes use lube before I try to stick it on, ya know what I mean?!

jakec · « **Reply #4 on:** March 17, 2018, 06:22:20 PM »

Thanks for the response. I tried to do some research on the fuel nipple but the part has no name or number so it is hard to search for online. If the swiveling is normal then I will just persevere to get a line on there somehow.

As for the piston, are you saying that I should put fluid in and then apply more and more pressure until the piston pops off? And can you confirm that it is not depressed all the way currently? Do you suggest using hydraulic pressure to get the piston off over using a clamp to push it in? The brakes were working amazingly before I took the wheel off, and then pulled the brake lever with the caliper not installed, which the manual says not to do and I think is what got me here.

ekpent · « **Reply #5 on:** March 17, 2018, 06:30:35 PM »

The piston should pretty much sit flush with the caliper when it is pushed all the way in. When I clean/rebuild mine I can easily push them in all the way by hand with no c clamps required. Is there too much fluid in the reservoir and it filling up tight when the piston is pushed in ? Watch your paint if you check if the tank is still installed !

Stev-o · « **Reply #6 on:** March 17, 2018, 06:47:50 PM »

Quote from: jakec on March 17, 2018, 06:22:20 PM

Do you suggest using hydraulic pressure to get the piston off

Yes, to get the piston out of the caliper.

jakec · « **Reply #7 on:** March 17, 2018, 07:05:24 PM »

There is no fluid in the system right now. The reservoir is emty and the bleen valve is open. If i squeeze the brake lever a little bit of fluid bubbles out but it's all pretty much gone at this point. Maybe I need to keep squeezing some more? There is no resistance on the brake lever at all at this point. The piston however feels immovable.

Bodi · « **Reply #8 on:** March 17, 2018, 07:39:04 PM »

Well you kinda messed up with the brake..
The easiest way to get the caliper piston out when it's tight is with the master cylinder. Now that you drained it ...

To push it in, bolt the caliper together with pads and pry between them.
To get it out you can try a compressor and air gun, blow into the brakeline hole with bleeder closed. This (if it works) will shoot the piston out with a lot of energy plus spray out the fluid in there. Wrapping it in many layers of towel will save a lot of trouble. You can also use a gease gun to force it out by removing the nipple socket, the stub will usually sorta thread into the line fitting well enough to seal ok.
You should get it apart for cleaning and to replace the seal. Honestly, buying a repop from David Silver is your best bet. After 40 years the inside will be corroded enough that cleaning the seal groove properly is impossible or close to it. And the brake will not work properly, dragging and squealing.
Carbs... they need some work. You should pull the rack out and inspect inside the bowls. That will tell you how much work they need ... clean and shiny means a general cleaning and probably new float valves - after taking the rack out and getting it back in once, you will appreciate that avoiding doing that again chasing dribbling overflows is worth the price of new valves. If the bowls are full of tarry goo or show corrosion then a better cleaning is called for, jets and emulsion tubes out for cleaning and internal passages cleaned and blown out. Avoid breaking the rack down unless unavoidable because fuel is leaking from the crossovers - the tee for the petcock line and the two straight through ones. The have o-rings that decay especially in gasahol.

jakec · « **Reply #9 on:** March 17, 2018, 07:46:58 PM »

Yeah, I want to push the piston back in, not get it out. The brakes were working really well before so I am not trying to rebuild the piston right now. I just want to get my bike back together.

I totally bled my brakes out because I thought that would let me push the piston back in. I already tried putting the caliper together and prying with a flathead screwdriver, and that didn't do anything. I just triple check and there's NO fluid in there so what's keeping the piston pushed out?

As for the carbs its not the bowls that are leaking and I'm also pretty sure it's not the crossover tubes either. I think it was the old fuel line which would have some dislodged when I was yanking at it to disconnect the tank last week.

I just reread another response that said if the return hole was clogged it could stop the piston from receding. How can I tell if its clogged?

I just did some reading in this thread

http://forums.sohc4.net/index.php?topic=15818.0

And it seems that if the piston was stuck engaged because of a blocked return passage, then opening the bleed valve would let it recede, which has not been the case for me.

Yamahawk · « **Reply #10 on:** March 18, 2018, 02:53:47 AM »

Go to HF and get a C-clamp. It's your friend for pressing in pistons in your caliper, make sure to use an old brake pad to press it in with. If your return hole in the MC is blocked, it needs cleaning, and flush you brake system out. Use a new bottle of DOT3-4 synthetic (I like Valvoline) fluid to replace/flush. Get the big bottle lol. Brake fluid is hygroscopic, which means it absorbs water... even out of the air. SO, if the piston is stuck, follow the advice given, and use the brake fluid in the system (you will have to fill AND bleed to remove air) to pop out the piston, and thoroughly clean the inside of the caliper, seal and groove. If the seal looks ok, re-use it, if not, replace it. The return hole in the MC is so small, it blocks easily, so cleanliness in the MC is a must. I found the smallest wire in a set of tip cleaners will sometimes work to clear that hole. If you don't get it unblocked, the piston won't retract.
Charlie

strynboen · « **Reply #11 on:** March 18, 2018, 04:56:43 AM »

no...you vant to get that piston aut..and thange the seal..and thek for korosion..its the only vay to get on...that piston can be pressed in use 2 fingers..if all is ok...if you not can do that..the piston can not return to neutral posision after have been push aut to brake,,,it need to move back. to free up the disc...or it vill rub against the disc all day....(only bu the rubber seals ovn elasticy..make it go free)..and that is not a big force... so to make a half job on a vital system, like the brakes.(..is a kind of shoting you self)

Stev-o · « **Reply #12 on:** March 18, 2018, 08:22:17 AM »

Quote from: strynboen on March 18, 2018, 04:56:43 AM

no...you vant to get that piston aut...

At least three of us have advised him to do so, but he doesn't listen.
I don't know why he asks for help??

strynboen · « **Reply #13 on:** March 18, 2018, 09:55:25 AM »

yes..after to have done 5-6 bikes..you get a idea of the going..its alvays the same split the komplet front fork and brake system..and klean all old oil aut ,,and new seals and oil..inn and yoy can go to the carburetors...and then to battery ald elektric..and then to cam thain tensioner..tires thains..and on and on...

ve have all been at the start ..it a bit hard to focus..and learn your ovn vay...he vill learn it..either the hard vay or aur vay(vho is the easyest)

Bodi · « **Reply #14 on:** March 18, 2018, 10:35:47 AM »

"just triple check and there's NO fluid in there so what's keeping the piston pushed out?"

There is the big question. You are a fool if you don't find out. I have had a bike lose front brake (cable broke) in a dangerous situation - and I'm very lucky to be alive now. I have no idea how I avoided a crash, I didn't then and still do not have the skill to perform the maneouver I did.

Do what you want. It's your bike and life. Try not to maim or kill anyone esle.

jakec · « **Reply #15 on:** March 18, 2018, 10:57:09 AM »

I was not understanding whether removing the piston is the solution to the problem or something you want me to do for posterity's sake. Yamahawk your response is much appreciated although it's still unclear, you said that a C clamp would be good for pushing in the piston, however you also said that if I need a C clamp to push it in I might as well take it off? Is that right?

I read about removing pistons with fluid, air, grease and how difficult they can be to remove and how they can shoot off. If I push it off with hydraulic pressure will it be pretty safe?

Also a follow up question, when the manual refers to the torque rating of the "front brake linkage" is it referring to the banjo bolts (that this bike for some reason uses like 6 of for one brake)?

ekpent · « **Reply #16 on:** March 18, 2018, 04:01:20 PM »

With the hydraulic pressure from master fluid will start to pour out first then it will just fall out but best to guide it. Be sure to have a catch pan under it to catch the fluid.

jakec · « **Reply #17 on:** March 18, 2018, 06:26:44 PM »

Ok, so I was able to push the piston out with the master. It came out easily. I looked in the cylinder and it was nice and clean in there, so I pushed the piston back in and it went all the way in easily. Bleeding the brakes took a really long time, but eventually it all worked out. The brake is operating normally. I'm not sure what was keeping the piston from going in originally but it's operating normally now.

Once I got the brake working fine I started pushing down on the forks to see how they reacted, and they were a bit clunky and loud so I drained the oil. One side was purple and the other was brown! I put in about 3.5 - 4 oz of ATF per the manual, and the forks are still a bit loud. When you compress them they make a clunk noise. Is this due to old springs? On my CL175 I ended up doubling down on the ATF and my forks went from occasionally click-clacking and feeling loose, to being quieter and stiffer.

Finally I will have to figure out a way to install that fuel line and maybe I can start my bike.

strynboen · « **Reply #18 on:** March 19, 2018, 06:46:35 AM »

this bikes like somthing thikket the atf..vho is abaut 5-8 sae....you can mix hydralik oil vith atf..to get the soft spot.(i do the fine that vay) adjust ..or go baying some sae 10-15 fork oil

do not overfill ekstreme, to hardent up the fork.

.it vill hardent the forks up like stone..you go from soft to stone hard in a fev mililitters oil difference..so riding and heat can give the same ekstreme thange..vho can give lost stering...better go vith thikker oil..and a very small overfill

jakec · « **Reply #19 on:** March 19, 2018, 03:28:57 PM »

When I overfilled my CL forks it was because they would make lots of noise every time they fully extended, and they were pretty soft and springy. When I would put it up on the center stand the front forks would make a click clack noise as they extended fully and the front wheel was momentarily suspended.

On the 400, its more like a consistent click noise every time the fork are depressed. Like every time it passes a certain point it makes this stiff click noise. Right now it has the recommended oil level. I feel like that would be pretty uncomfortably when riding. Do you think that click when compressing is more likely due to old springs or bad oil level?

strynboen · « **Reply #20 on:** March 20, 2018, 11:58:03 AM »

i think it are all,inn to the thin atf

..its just too thin for a veared 40 years old fork

.on my 500 twin the forks ..vas very veared..aut,,but still, the thikker oil made it run fine..just used new seals to hold the oil inside...and vater autside..so it not rottens aut..its vater in the oil vho make it go rotten...and in time vill rust..and mix in the oil and vear the internal parts aut

you vill finn as soon yoy starts ride the bike..it vill start leak fork oil..

jakec · « **Reply #21 on:** March 20, 2018, 12:24:45 PM »

I rode the bike yesterday and today. Are you saying it should start to leak oil? Because I checked the seals and they are really good, although a bit dusty. The dust covers were cracked but I zip tied them on for now. When riding the bike I didn't notice the forks being clunky anymore, although I am not riding it hard or leaning over as the tires have only 5 miles on them at this point.

News:

Author Topic: CB400F - Brake Caliper Installation & Fuel Leak (Read 3310 times)