Rear disc keeps locking up!!

[Ridgeline]

Hi Guys and Gals, I read a few threads in the search and followed the suggestions that were there IE: Changed brake fluid to Dot 4, completely bled the system and tried it a couple of times and everything was fine but I just got home and it stuck again!! It seems to only happen when I give it a hard shot on the brake or use it too much.

The disc is a little black now and does not seem warped at all so it's tracking true, by it being Blued will this affect it or not? Any suggestions or help would be great guys!

[msRandi]

should not be happening. check the brake pedal stop bolt and the linkage. there has to be play in the linkage if there is no play check pedel stop ajust bolt. other thing is over filling brake resavor or pluged vent in the filler cap. the last thing would be piston stucking in calaper.if you do a lot of durt riding it could be the later.
hope any of this helps

[Ridgeline]

Bike is new 150 miles on it so I don't think there is a dirt issue (have not been out on the trails yet). I see that there are 2 bolt on the rear brake lever one is the stop bolt and it's good, the res. vent is not plugged and the res. is halfway between the min/max line , there is also the back bolt that contacts the hydraulic plunger for the caliper activation. Do you think that might need adjusting also and if so what sort of play is suppose to be in there if there should be any at all which is what I think it should be. Thanks for the info and I am still searching... What about the disc being a bit blue?

Your problem is as common as Fleas on a Dawg, adjust the pedal stop until the adjusting bolt coming out of the Master Cylinder and connected to the rear of the pedal is slightly loose with no tension on it.

If the pedal stop wont adjust far enough pull the nut off and grind it down far enough for the pedal to come up a little more.

[Ridgeline]

That's the d___ problem!! I will remove the bolt and make sure it's got play since I can't back it off any more and it still gives pressure! What about the disc?? Is there any thing I can do or is it still good or not?? I just checked it and it's more of a greyish/blackish colour and still runs true...

Dont worry about the disc, take some 180 grit or so sandpaper and knock the glaze off, make it rough so the pads will reseat. It will be fine.

[msRandi]

that right on the money.

[Ridgeline]

All done will give the test tomorrow, hope all goes well! Thanks guys...

[molypod]

Ridge,
my rear brake is real touchy as well and it only takes a slight bit of pressure to have it skid(lock the brakes) in the dirt. On the road it takes a little more pressure in the wet to lock it up. I use 90% front braking on both dirt&road because of this. I've tried adjusting the linkage and all it did was ease my mind as I can depress the pedal a little further till it locks up but I don't feel any diference on the braking. My old CR 125 used to do the same. Some bike just have a real sensitive rear brake and it'll take some getting used to. On downhill switchbacks it can help to skid the rear a bit to kick it around the sharp corner or you can use alot of front brake and "hop the back around" Reminds me of downhill skiing in deep powder "Jump turning.."
anyways I'm off topic now.
Also I'm going riding today and will take pics..

[Jim]

I think the pedal may be a little high compared to the footpeg too, making it a little harder to judge the applied pressure...

But that is the skidding problem, the problem you had sounds like what was mentioned with the adjustment

[Ridgeline]

She's all good now!!! Drove around town today without any problems and so far so good! The bike has been pretty good with that being the biggest problem to date, very little minor things that got taken care of that were overlooked during the build up...

[TheOtherRide]

Yay! Glad it worked for you.

[katoranger]

Mine locked up and stuck today and I had to remove one of the caliper bolts and swing the caliper back against the swingarm to get to work. I have already adjusted the stop bolt all the way in and it was working fine until today.

I plan to bleed it and take the stop bolt out to see if that helps.

Thanks for the info.

Allen

[TeamCheap]

This seems to be a reocurring problem on ours, not so much anymore but it did just happen to me last weekend.

We were going to the autoparts store and I noticed rear brake fade just as I pulled in and knew what was up.

Got my part came out and pulled the tools out and thought I'd just run the adjusting bolt in a touch but it was already in all the way so I'm stuck.

Then I had an idea, just put some pressure on the brake lever and carefully open the bleeder.
A quick open and close let out a few drops of fluid and I was good to go.The caliper backed off the rotor and it was fine.

[katoranger]

I will have to try that tommorrow before I go to work to see if I can get it free. I am wondering if there is air in mine since I haven't bled the system. I am also wondering if the "NOS" bottle has something to do with it.

Allen

[TeamCheap]

If the brakes feel solid then there is most likely NO air in it if it's soft/spongy feeling then there is air in it.

I dont have the "nos" bottle on the rear of mine so it's not causing the problem unless the bottle in some way would stop it from happening.

[katoranger]

Yes, the front doesn't have any problems. I never check to see if it was overfilled either. Might just need to bleed it off after I reattach it.

Allen

[vmtz]

I just got my bike last week and on the second ride it locked up. I adjusted the stop bolt all the way up and did another 25 miles yesterday with lots of stop and go, so far so good.


Vince

[katoranger]

Ok, I went out and basically bled out the rear brake system and it seems to be working fine now. I have some more travel in the pedal too. I don't use the rear alot except in off-road riding or hard stops.

I will see if it sticks again today as the two times it happen to me it occur almost in the same place.

Allen

[katoranger]

Okay, I made it about 15 miles and it stuck again. I never even touched the rear brake. I did as teamcheap suggested and cracked the bleeder and it released. I made it the rest of the way to work and all the way home with no problems.

I packed the 8mm wrench to use.

Allen

[fatboy250]

Check out http://www.chinariders.net/modules.php?name=Forums&file=viewtopic&t=172&start=30 about midways down. I posted a comment about this.

This is probably the issue. There are others who have done this mod since to fix the problem too. Just do a search.

Jason

[katoranger]

Thanks. That is where I will look next. I suspected it after the first time it happen and I was able to adjust the pedal stop and release it. I have the "proper" tools described to fix it.

Also I am going to check the steering nut to make sure it is tight.

Thanks, Allen

[katoranger]

This is from fatboy. I am just adding a picture.

For Roketa Models:

Ok, Dad and I have figured out the deal on this. If you look at the bottom of your rear break master cylinder (not the slave at the wheel) you will see where the armature pushing in has two linkages with a bolt and two nuts for adjustment. Well, even with the nuts in the lowest setting where the linkages are both resting on the top nut, the master cylinder armature is still being pushed into the master cylinder creating some pressure. So, you will need to permanantly remove the nut between the two linkages and shorten the bolt (a grinding wheel may work well) so that the two linkages are touching. This will allow the master cylinder armature to release all the way out. We believe it's not necessarily a design flaw, but more of where the weld ended up for the bracket that holds both the rear foot peg bracket and the master cylinder. If this bracket weld had been about 1/2" higher the master cylinder armature would be allowed to extend all the way out with the stock bolt and nuts adjustment.

Here is a picture of the master cylinder on my bike.

http://www.chinariders.net/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=5385&g2_serialNumber

Now the linkage you are talking about is the actuater rod for the master right. Gold colored part. I didn't have any more problems today so I haven't touched it yet.

I did find out that one of the caliper bolts was contacting the rotor and left a nice gouge in it.

http://www.chinariders.net/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=5390&g2_serialNumber

Allen

[fatboy250]

Yeah here is the picture of mine after the nut was removed. http://www.chinariders.net/gallery2/main.php?g2_itemId=3385

Jason

[katoranger]

Okay. I think I understand it now. I think your master is slightly different.

What kind of tire is that?

Dunlap?

Allen

[pumpkin]

katoranger,

after i adjusted my pedal just like yours mine still hung up so i allso had to adjust linkage on the master cyl. there isn't much adjustment ,but for my bike it was just engh.

[jkomp316]

on my GY-5 I had to adjust the stop nut and that was it. if you go up far enough or take the nut out, the pedal just hits on the kick starter. i have the stop bolt stopping it just before that. havent had any problems yet.

[katoranger]

Thanks, so far I haven't had anymore problems. I won't ride tonight due to an impending storm approaching from Alabama, but I hopefully again on Wednesday. Starting to accumulate miles finally. Bike keeps running better with time too.

Allen

[fatboy250]

What kind of tire is that?
Dunlap?
Allen

Linked in the Cross Reference thread -- Cheng Shin Barracuda

[katoranger]

Thanks, it may end up with street tires after these wear out.

Allen

[katoranger]

Okay it stuck again today twice. I will be making some adjustment tomorrow. I pulled off the road to fix the brake and I notice the kickstand wouldn't go down. Found the bolt almost backed out and the spring was catching on it. Will have to safety wire it.

Also found out the hard way how far it will go on a tank a gas and that the reserve is only good for 2 kilometers.

I had to push it 1/4mile to the gas station. It worked out to 76mpg.

Allen

[AZ200cc]

Could have been worse.. A 1/4 mile is not that bad, but it still had to suck.

[TheOtherRide]

Do you add your pushing into the mpg calculation? :P

[fatboy250]

Also found out the hard way how far it will go on a tank a gas and that the reserve is only good for 2 kilometers.

I had to push it 1/4mile to the gas station. It worked out to 76mpg.

Allen

At least you know exactly how many miles you can go now. That's a good thing if you ever have to stretch a tank.

Jason

[katoranger]

Ok, I think I have the master adjuster so it releases all the way. I was able to use the adjustment point on the pedal/master connection. I seems to be working fine now.

My push was in 95 degree heat while wearing a leather riding jacket. I did look at the odo when it quit and use it for the mpg calculation. It is not exact as I first convert the km to miles then divide by the number of gallons.

I sorta of intentionally ran out of gas to find out the limits. I know now to fill up by 200km.

Allen

[erod]

I am having the same lock up problem with my almost new um bike. It does it at really strange times.

Has anyone thought of just replacing the brake with an old fashioned manual brake and getting rid of the hydrolic mess?

Does anyone know what bike the um dsf 200 is a model of so I could get a good matching manual brake?

Thanks for any help.

[katoranger]

Adjusting the master cylinder so that the plunger comes all the way back has seem to solve the problem on my bike. I have donw about 200 miles with no repeat problems now.

I may be possible to sway over a drum wheel and brake assembly, but try adjusting the master first.

Allen

[katoranger]

Having brake problems again. Been a few months, but its back.

I will see if there is more adjustment.

Allen

[katoranger]

Well, I think it was as simple as too low on brake fluid. Was just barely covering the hole in bottom.

Added fluid and bled system and then took it for a ride with no problems.

[katoranger]

Update again. I had adjusted it some more, but it was still dragging this morning.

I have it adjusted as far as is can currently go. I will have to remove the master and cut the plunger bolt off to adjust it further.

Allen