I got the caliper all cleaned up with the picks and then ran a small piece of scotchbrite through the groove. Cleaned it up well.
It's reassembled and back on the bike. Next to check the master and then bleed.
EDIT -- This thread was split from Turning Wrenches »Rear caliper seized. What now? (http://www.2strokeworld.net/forum/index.php?topic=1619.0) since this issue has grown into a topic of its own and does not involve a stuck caliper
Let us know how the master cylinder comes out. The bleeding should be a piece of cake.
Lyn
No dice. :bang:
Caliper is rebuilt and recently painted. Completely disassmbled, cleaned, painted, and reassembled the rear master. Reassembled the system with new crush washers. It looks great but doesn't work at all. It won't build any pressure with the master and I can't pull any fluid from the caliper even with a Mity-Vac. This rear brake has been the biggest exercise in frustration over the past few years.
Try reverse bleeding the rear caliper.
@SoCal350
Might sound dumb, but did you clear out the bleed screw? I've run across some that were plugged solid in the past and had to use safety wire to clear out the clog. One of my mentors also had me start bleeding from the banjo bolt on the master to get things started in the past. In other words squeeze the lever (or press the brake pedal) and crack the banjo bolt loose to let air out.
Quote from: Evans Ward on October 07, 2020, 11:38:53 PM
Try reverse bleeding the rear caliper.
That may be next. I'll need to replace the speed bleeder with a standard one and purchase a reverse bleed kit.
Quote from: Diablo007 on October 07, 2020, 11:45:37 PM
Might sound dumb, but did you clear out the bleed screw?
The bleed screw is a brand new Goodridge speed bleeder. The only component of the entire system that has not been touched and/or replaced with new is the aftermarket braided SS hose.
Attached photo shows the order the parts were assembled in the master.
Yes, pre-bleeding the master at its banjo is probably your missing link. Without that, they won't draw fluid from the reservoir to pump into the system. In other words, "prime the pump". Vacuum bleeding can only put a maximum of 1 atmosphere pressure on the fluid to move it past the spring-loaded piston. Get fluid in there, and you have many atmosphere's pressure available to move the fluid.
Spent several more hours on it. No love. :bang:
-Left the pedal depressed overnight.
-Removed the master banjo and I can see the fluid rise to the top of the bore and barely spill out when the pedal is pressed down. When the pedal is released the level drops back down inside.
-Cracked the caliper banjo and a tiny bit of fluid seeps out.
-Removed the bleeder screw and a little fluid squirted out when the pedal was depressed.
-Tried pulling fluid through again with the Mighty-Vac but only got a tiny bit.
-Swapped speed bleeder out and installed regular bleeder with teflon tape on threads. No change.
What's been done so far:
New master rebuild kit
New caliper seal kit
New reservoir hose
New copper washer on reservoir fitting
New copper banjo crush washers, x4
New Goodridge speed bleeder (also tried clean stock type bleeder with teflon tape on threads)
Master disassembled and cleaned twice -- ultrasonic, brake cleaner, air, small pick. Bore clean and smooth, both holes confirmed clean and clear.
Caliper disassembled and cleaned twice -- ultrasonic, brake cleaner, dental pick. Bore confirmed clean and smooth, All passages clean. Piston is clean and smooth.
-Reverse bleeder kit will be here Tues 10/13. I may not wait that long.
-I have an RD400G rear master here which is the same part, which I could also try but it will need to be cleaned up and rebuilt first.
-I also have a NOS Ducati Brembo master that I may try but I need to make a mounting bracket first, which will be difficult since I don't have much in the way of equipment for fabbing. Reservoir fitting is also a different diameter (smaller). I purchased it a while back with the intention of upgrading one of my RD400 rears at some point.
I've had good results pushing fluid into the bleeder fitting on the caliper with a large syringe. You have to watch the fluid level in the reservoir so that it doesn't overflow. Syringe is cheap at a farm supply store.
I'm confident reverse bleeding will solve your issue. Like you, I tried many methods on my rear stock RZ brake caliper before trying reverse bleeding. I bought a nice kit off Amazon that I've also used successfully for an automotive application so I'm sold on reverse bleeding. As mentioned, you don't have to spend the big bucks on a kit and can use a large animal syringe or the like.
I've never been able to bleed a rear brake on a RD without doing the reverse bleed, push fluid in the caliper and keep going until you see it come up to the reservoir.
Starting to get the idea there is a black cloud hanging over this brake system. The USPS package with my reverse bleeder kit, which I have been eagerly awaiting, was to be delivered today. However, I watched the mailman drive up (6-8 hrs later than normal) and put only regular mail in my mailbox, no package, and drive off. Went out and looked and sure enough no package. :bang: Yet, the tracking was marked as "Delivered In/At Mailbox" with the same time stamp as when the postal moron was at my mailbox.
This isn't something new, mail delivery and accuracy has been a big shortcoming for the past 3-5 years. This is the 3rd time this has happened this year. Only 1 of the previous 2 missing packages was ever found. So I'm still without a brake bleed kit unless it miraculously shows up somehow.
F*ck the USPS!
:tellit:
Our mail came four hours later than normal due to COVID + Columbus Day + weekend combination. Our carrier has delivered to wrong address, then gone back and corrected. Not an easy job, but would be appreciated if more care was taken. And if the package is really needed, seems you can count on late/incorrect/lost. But the advertisements will be there!
Ordered a 2nd reverse bleed kit. Only 2 days for delivery and this time I saw the guy scan it at my mailbox. (Shipment #1 is still MIA but I filed a missing shipment claim with USPS.)
So...the 'magic' reverse brake bleeder works great. But it didn't solve my problem. :eek: I pushed fluid through 3 times -- 3 full reservoirs of fluid from the caliper. Still no pedal resistance and the caliper piston doesn't move. Didn't notice any air bubbles coming up in the reservoir cup. And I have no leaks, which I guess is good, considering. I even unbolted the caliper and dropped it down to ground level and put my hand on the piston when pressing the pedal and didn't feel anything.
Well, now for plan B...err I mean plan J. Plan B was a long time ago. :bang:
Sounds like (sorry) the MC is assembled wrong. Look at some photos of disassemblies. I had one with the rear cup in the wrong position (from the vendor), and another where the cup slipped into the wrong spot because I didn't use brake fluid to lubricate it all on assembly. Most MCs have two rubber cups - one on the outlet spring and one on the piston rod. Both open towards the outlet. On the RDs, there is also a thin disk that works as a check valve between the front cup and the end of the piston. Make sure the disk is present, flat, and the holes in that end of the piston are clear. And that the second cup is behind the knob on the piston rod, not slipped forward past it.
Quote from: pidjones on October 18, 2020, 07:48:43 PM
Sounds like (sorry) the MC is assembled wrong. Look at some photos of disassemblies. I had one with the rear cup in the wrong position (from the vendor), and another where the cup slipped into the wrong spot because I didn't use brake fluid to lubricate it all on assembly. Most MCs have two rubber cups - one on the outlet spring and one on the piston rod. Both open towards the outlet. On the RDs, there is also a thin disk that works as a check valve between the front cup and the end of the piston. Make sure the disk is present, flat, and the holes in that end of the piston are clear. And that the second cup is behind the knob on the piston rod, not slipped forward past it.
Thanks for the continued input and help :thumbs:
See the photo above from Oct 7 for the assembly order used.
The holes in the piston head should be clear. It was run through the ultrasonic several times during this long ordeal and during the last assembly I ran a fine copper wire strand through the holes to ensure they were open.
To be clear- what bike is this on? I've seen the rubber cup under the spring invert incorrectly upon assembly. I use my pinky finger to seat it so that doesn't happen.
Quote from: Evans Ward on October 18, 2020, 08:58:53 PM
To be clear- what bike is this on?
RD400F rear (Note: I just split this into a new thread of its own since it was originally part of another topic on brakes)
Latest non-progess report...
Today I removed the master again and confirmed the internal parts were in the correct order. Everything looked OK. However I decided to rebuild it
again with a
new OEM piston seal and rubber cap. Parts were installed in the same order as shown in the Economy Cycle reference image. (see attached photo) During assembly I verified the rubber cap was inserted with the correct orientation and did not flip over. Both the seal and the rubber cap have the "open" end of the seal flange facing the brake line as shown in the photo.
Also removed the caliper and confirmed the piston is free and can be pushed in by hand. I put a small piece of wood in it and put 25psi compressed air into the caliper to confirm it would move out, which it did.
Reassembled everything, reverse bled twice, then traditional bled sveeral times but still no dice. At least there is a little firmness in the pedal now and I can feel/see the caliper piston moving slightly. There is still not enough pressure to firmly clamp the pads to the rotor so they rattle if the caliper is rocked back and forth.
Going to let it sit overnight and tackle it again tomorrow. :whatever:
Oddly enough I had a similar problem this past weekend with a rebuilt master on an RD350. I ended up removing the hard line from the caliper, put my finger over it and squeezed the lever, released my finger, put my finger back over it, and repeated until pressure built up in the line enough to squirt fluid when I removed my finger. At that point I reattached the hard line and was able to bleed the brake. It seems at this point it may be worth a try. You could also remove the master and attach it to a piece of handle bar and so the same thing with the master only, finger over the banjo bolt hole. In hindsight that probably would be better as you won't risk brake fluid on your newly painted caliper. I wanted to make sure the brake line wasn't the problem and with an RD350 removing all the fittings to test would have been a pain. Probably not so much for the rear brake system on your RD400.
^ i wind up doing this more often than not, its good advice.
^ I've had to do this on new Chinese MCs as well as rebuilt Honda MCs. I call it priming the MC.
Disconnected the hose at the caliper. Squeezed in between my fingers and pressed the pedal a few times. Couldn't hold back the pressure with my fingers so I succeeded in spraying/misting brake fluid in my work area and on the rear wheel. Bolted it back up tried bleeding a few times. Still not much resistance on the pedal and the caliper piston barely moves (but does not slide out of the bore and firmly contact the pad) when pressing the pedal down.
At this point it the problem seems to be the brake caliper itself. To me it sounds like there's a leak letting the air in the caliper out and then back in as you haven't mentioned brake fluid leaking from any caliper seals. I'd take the caliper apart and inspect the seals and sealing surfaces.
A few more thoughts: Is the pushrod adjusted to have that little bit of play that makes sure the piston is coming back all the way? When you push the petal down and then open the bleeder, close the bleeder and let the petal back up slowly and wait a little while before touching the petal again. Before you do go to push it again gently tap the petal several times so the pushrod is just barely moving the piston. Then continue with a full push of the petal.
Quote from: Diablo007 on October 21, 2020, 01:31:40 AM
At this point it the problem seems to be the brake caliper itself. To me it sounds like there's a leak letting the air in the caliper out and then back in as you haven't mentioned brake fluid leaking from any caliper seals. I'd take the caliper apart and inspect the seals and sealing surfaces.
The caliper has been apart a few times. Earlier this month I disassembled, cleaned and inspected it again. Made sure the seal groove was clean, bore and piston are smooth and clean with no pitting or corrosion, lubed the new seal with red rubber grease, and put it back on the bike. I plan to remove the caliper again to disassemble, inspect, and reassemble. I may even put another seal in it just because.
Quote from: 1976RD400C on October 21, 2020, 06:05:44 AM
A few more thoughts: Is the pushrod adjusted to have that little bit of play that makes sure the piston is coming back all the way? When you push the petal down and then open the bleeder, close the bleeder and let the petal back up slowly and wait a little while before touching the petal again. Before you do go to push it again gently tap the petal several times so the pushrod is just barely moving the piston. Then continue with a full push of the petal.
There is free play in the pushrod. I tried slow pedal depresses with a pause between each depress. In fact, I've tried just about every method I could think of. I also waited 10-15 min between each bleed attempt. I'll give it another go sometime this week. But it's seeming like Groundhog Day.
Might be time to test with a known good caliper if you have one, or a different known good master.
These are some longshots but things I have seen over the years:
The bleeder isn't compatable with the caliper. It fits and is open but fluid won't flow.
Same with the banjo bolt, the holes are free but won't line up with the opening in the banjo fitting.
The brake line is weak internally and when bent it collapses and blocks flow.
Try taking the bleed screw out and letting it gravity bleed, if you don't get fluid try it at the banjo fitting.
At this point we know the master is good. Sorry, forgot you tested it. If you're 100% that the caliper rebuild is good these are the things that come to mind.
Being an IT guy I've learned (and relearned) that we sometimes forget the obvious:
Is this the original system that was on the motorcycle?
Was it working before the rebuild?
If so, what was the reason for the rebuild?
Was the hardline to the caliper replaced?
If so does it fit properly? (In a thread I started regarding brake calipers it was mentioned the RD350 front brake and RD400 rear brake look similar but use different hard lines. Something I had noticed when going through milk crate full of miscellaneous masters and brakes in the shop.)
As we know the master builds pressure if we assume fluid/air is moving in the line we can test for leaks in the system. Since you haven't noticed any brake fluid leaks, test the same way you would during a leak down test. Spray soapy water on the fitting, then pump the brake lever and look for bubbles. I'd start with the easy stuff, the hard line junction and the bleeder bolt. The caliper would be a bit of a pain.
Hoping this will help! If not, I'm at a loss.
Quote from: Diablo007 on October 22, 2020, 01:57:41 PM
Is this the original system that was on the motorcycle?
Was it working before the rebuild?
If so, what was the reason for the rebuild?
Was the hardline to the caliper replaced?
If so does it fit properly? (In a thread I started regarding brake calipers it was mentioned the RD350 front brake and RD400 rear brake look similar but use different hard lines. Something I had noticed when going through milk crate full of miscellaneous masters and brakes in the shop.)
Yes, caliper and master are stock originals.
Yes, it was working before the rebuild and it has worked ever since I bought the bike in about 2006. The entire system has been on the bike since I bought it. The only replaced items are: new OEM Yamaha master rebuild kit (2 different ones), new K&L caliper seal kit (2 different ones). new copper crush washers, new banjo bolt on master.
It was taken apart for rebuild because the master seal was leaking and causing crusty crystals to form around the bottom of the housing.
There is no hardline. This is a rear RD400F Daytona. The original hose has been replaced with a braided SS line. (refer to photos I posted on Oct 7 above)
The master is unique to the Daytona but uses the same rebuild kit as the '76-'78 1A1 models. The caliper is unique to the Daytona (1-year-only unit, and front and rear are not interchangeable). The bleed screw currently installed is the original and is the correct M8 x 1.25. Banjo bolts are the correct M10 x 1.25.
There are no leaks anywhere in the system currently. All banjo washers have been replaced with new copper. The master is clean and dry and not showing signs of leaking. The caliper also shows no signs of leaking.
I had a bike that a PO had replaced a banjo bolt. But, there wasn't a hole in it!
Thinking simple still, perhaps your new line has been over crimped? Only way to test would be to remove and push air through it...
Hardy
Quote from: Hardy on October 25, 2020, 02:41:10 AM
Thinking simple still, perhaps your new line has been over crimped? Only way to test would be to remove and push air through it...
The brake hose is not new. It's the same braided SS one that has been on the bike since I have owned it, and the brake was working fine with this hose prior to rebuilding.
since you're not sure what the problem is I would do exactly what you did and troubleshoot one component at a time.
after re- reading - the only thing that hasn't been checked is the brake line itself and although you say it's good I would definitely check it and verify that it is in fact good so you can rule it out or if it's found bad change it.
Good Luck!