Two Stroke Motocross
Two Stroke Motocross Forum => Technical => Topic started by: Braap257 on August 13, 2010, 07:49:15 AM
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Okay so last night after i finally got that old oil drain plug out i decided to check on the brakes. The rear is solid. The front however feels quite spongey and the fluid is old. so i changed the fluid and rebled the brakes with my brother the problem is they dont seem to get firm like i want them.... and every time he fills the reservoir there is a bubble on the 1st squeeze of the lever. What does that mean??? I guess what I'm really asking is how to get the front brake nice and firm???
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Sounds like your master cylinder needs to be rebuilt aswell as the caliper. A factory shop manual will show you how to do this. You are only replacing seals and cleaning out old gummy fluid. Remember to polish the pucks in the caliper unless they are teflon then leave them alone.
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First things first. Be 100% positive you bled them thoroughly and got all the air out. Then check the screw on the lever and be sure it is adjusted so it's pushing the plunger in far enough.
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Is it possible to back bleed them? On my KTM, I have a hydraulic clutch. When I changed the fluid, I cracked open the bleeder, then with a syringe and a small piece of tubing from the local farm and feed store, I pushed fluid back through the system.
Just a thought.
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Unbolt your caliper and take out your slide pins and pads.Clean the anchor where the pads slide and put a little grease there as well.Clean your pins a put some grease on them as well(silicone type brake grease).A slightly binding slide will give you a spongy brake.A slightly bent rotor will as well but the brake firmness will increase with your second pump when sitting still if that's the case.
Once its done and all put back together,put your thumbs against the caliper while grabbing the anchor with your fingers and push hard so your caliper piston goes all the way in(I do this after every ride as well front and rear-especially if I've been upside down)This will force the fluid back up in to your master cylinder along with any air.That little bubble you see is normal.If you see many-it's not and it's rebuild time.Normal bleed procedure is to pump your lever and while holding it in,crack your bleeder until the lever goes to the bar then tighten the bleeder.repeat.Bike systems typically trap air when disassembled.Tapping the joints and leaving it sit overnight then rebleeding helps.
The first time you push the piston back with your thumbs,take the cover off so the fluid will overflow then repump the lever while refilling.
When you do it after a ride with the covers on,the rear will push back much easier and farther than the front due to the extra space in the reservoir.
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So when bleeding you should pump the lever then while pressed crack the bleeder screw open and let the lever hit the bars? Idk how long you are supposed to keep the bleeder cracked open, how hard the lever should be pressed.. ect..
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Yep,pump it a couple times then hold it firmly and open the bleeder until the lever hits the bar then while holding it there,tighten the bleeder and repeat.As soon as you open the bleeder the lever will hit the bar so you just end up holding it a second or so.
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Okay thanks Ford I will try that.
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I got them! They feel perfect. No sponginess whatsoever!!! I just bled and bled and bled and finally the lever smoothly goes back and is nice and responsive. ;)
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Thanks for posting the cure and results. Glad you got her fixed....
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Thanks for posting the cure and results. Glad you got her fixed....
:)
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Call me naiive but... why do brakes even need fluid anyway? Is it that completely impossible to make a mechanical system that uses leverage to put pressure on the disks? Maybe I'm underestimating how much power those calipers lay down, but I've seen what kind of balls a clutch spring has and I imagine that crushing down five of those with the traditional system of levers and cables takes a lot of force, yet the traditional cable-and-lever system works quite well and is practically zero-maintenance. So do the brakes require that much more force than a clutch, or is there another reason (Maico and KTM clutches notwithstanding)?
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The reason is progress Jetz, not to mention hydraulics take a lot less effort for the same stopping power and/or clutch activation
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Is it really that important that you have to deal with threads like this? Sounds like this issue would've been a real bastard in pre-internet days. And, although it's easy to say "oh yes, add hydraulics" it seems like these smart people could come up with something simpler that provides a mechanical advantage. Simplicity is an end in itself; who wants to keep track of thirty different little fluid changes that need to be made, the failure of which can send the bike careening into oblivion? If there's something fundamental about disk brakes that require that much force, then I can't really complain. But, if they're just throwing on hydraulic this's and that's for marketing purposes, so they can brag about pulling stoppies when a fly lands on the lever, I can't see myself getting behind it.
And by the way, just to make it clear, I am not arguing in favor of ye olde drum brakes here, in case someone thought I was implying that.
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Hydraulic systems, jetz are one of the simplest systems going.
The Romans used hydraulic systems 1000 years ago. Using water.
Machanical systems are not practically maintenance free.
They are just a pain in the arse.
Hydraulics are not all voodoo and incense.
Have a ride on a modern euro bike with hydraulic clutch. Go for a 4 hour ride in some of the shittiest tracks you can find and i guarantee you will not want a cable clutch again.
Yes cable works fine , but once you have used hydraulic you will wonder why every bike does not have one.
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I can imagine that would be a big help. I once spent five minutes on a 440 Maico and that damn thing required a hand of forged titanium in order to use the clutch (although who in the hell uses the clutch on a 440 Maico, anyway?) However, I have never encountered a brake, front or back, that really required much force to pull in whatsoever. It's just been a non-issue, and the effectiveness of the brake hasn't seemed to have any effect on this. So that's why it seems peculiar to me that so few bikes have hydraulic clutches, and so many have hydraulic brake calipers. I would be curious to see a comparison on just how much force is required to disengage a clutch, versus how much force is required to clamp on the brake disks. Especially on the rear brake, I mean, the amount of power you can put down on a brake lever like that is practically endless. That's what makes me think that maybe there's something inherent to disk brakes that requires they be set up with fluids and hydraulics, rather than rods, cables and levers. Don't read too much into this, I'm not implying that one is better than the other, I'm just wondering why it be. If nothing else, it's got to cost a bit more, right?
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Magura makes a hydrolic clutch cable that allows for about 20% extra pull. I've seen them on 1981 Maicos before but I've been trying to contemplate seeing if I can find one that would work on my 1983 Maico, it's quite hard to pull. So is the 82, but I think the 83 is even worse. It requires a long cable though, so need to see if I can get a magura with a longer cable.
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Hydraulic systems, jetz are one of the simplest systems going.
The Romans used hydraulic systems 1000 years ago. Using water.
Machanical systems are not practically maintenance free.
They are just a pain in the arse.
Hydraulics are not all voodoo and incense.
Have a ride on a modern euro bike with hydraulic clutch. Go for a 4 hour ride in some of the shittiest tracks you can find and i guarantee you will not want a cable clutch again.
Yes cable works fine , but once you have used hydraulic you will wonder why every bike does not have one.
My 550 Berg clutch pull was similar,if not easier than a 125 cable type.There's really no comparison.
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Not to mention, self adjusting. I love the hydraulic clutch on my katoom
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How does the hydraulic clutch compare to the cabled?
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The pull is lighter / easier. With the cable you need to adjust the cable from time to time. The hydro is self adjusting.
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A tip on bleeding front brakes, unbolt the caliper and bleed it while the brake line is straight.
Air rises in the fluid, with the arch around the fork air has 2 way to go up. If you straighten it out and bleed its muuuch easier. :)
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Sometimes I crack the bango fitting next to the master cylinder if I am having problems bleeding a brake.
As stated in earlier posts, the beauty of hydraulic brakes and clutches is that they are self adjusting.