OzVMX Forum
Marque Remarks => Honda => Topic started by: Paul552 on January 01, 2014, 05:23:13 pm
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Front brakes are dragging on my 84 cr.
I have cleaned pistons
New brake line
New fluid
Re bleed is done and not leaking etc.
Anyone have experience with this before? Any causes???
Thank in advance for the help
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did you pop the pistons right out to clean them?
i do this and them give them a clean with fine steel wool soaked in brake fluid then clean. check for any pitting on the piston bores, install new seals and dust seals.
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did you pop the pistons right out to clean them?
i do this and them give them a clean with fine steel wool soaked in brake fluid then clean. check for any pitting on the piston bores, install new seals and dust seals.
Yep poped them out and cleaned the right up?
I can't work it out?
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Is the caliper floating properly ?
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so, if the brakes are dragging and you crack the bleed nipple, the dragging stops ? if it does it must be hydraulic, if it doesn't then it must be mechanical.....
Applying car mechanics to bikes. A cars disc pads come away from the rotor for 2 reasons, one is the deflection of the piston seal pulls the piston back after the pressure is released and a few thou run out of the rotor moves the pads back in conjunction with the seal.
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so, if the brakes are dragging and you crack the bleed nipple, the dragging stops ? if it does it must be hydraulic, if it doesn't then it must be mechanical.....
Applying car mechanics to bikes. A cars disc pads come away from the rotor for 2 reasons, one is the deflection of the piston seal pulls the piston back after the pressure is released and a few thou run out of the rotor moves the pads back in conjunction with the seal.
I will check if it releases after cracking the nipple?
If this releases the brake what does that mean?
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I remember having trouble once because I didn't leave any space in the reservoir so when the fluid got hot and expanded it had nowhere to go but to expand the pads, once I drained a bit of fluid out it was fine.
Otherwise it sounds like you have a sticky piston or as mentioned the caliper may not be floating smoothly.
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Thanks Geoff
Unfortunately it does it with cap removed :-[
How does the fluid return to reservoir ? It seems like the pressure builds up but and is not released ?
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If the brakes are staying on it may be hydraulic, if for some reason there is still pressure in the system keeping the pads in contact with the rotor and you open the bleeder (as long as its not blocked) and the brakes free up then for some reason the fluid is not getting back to the reservoir, there may be a problem at the master cylinder. Check that there is some clearance between the lever and the master cylinder piston too.
If opening the bleeder changes nothing the its reasonable to conclude its not hydraulic and the pads are being held against the rotor for another reason, pads jamming/seized on the slides, some sort of mechanical issue.
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Alright I will check by cracking the nipple
Thanks
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Check that the lever adjuster hasn't been adjusted up too far. It is possible for it to hold the piston in far enough to block off the bleed hole back to the reservoir.
Honda calipers seem to be quite prone to sticky pistons. Simply cleaning them isn't always enough. I've tried a smear of moly grease on the pistons/seals which worked about half the time.
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Check that the lever adjuster hasn't been adjusted up too far. It is possible for it to hold the piston in far enough to block off the bleed hole back to the reservoir.
Honda calipers seem to be quite prone to sticky pistons. Simply cleaning them isn't always enough. I've tried a smear of moly grease on the pistons/seals which worked about half the time.
Thanks again for the tip.
I recleaned and put some grease on the piston seals.
Same result?
It must be mechanical because once it has pressure ( brake applied) it still drags even after the hose is removed.
If you pump it with pads removed you can see the pistons backing off.
Maybe a bent pin ? It seems to float ok though???
If any one has a caliper surplus to there needs please drop me a pm.
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you need to remove the seals in the caliper and clean behind them then install new seals and dust seals had the same problem with my 84 250 some years ago the old brake fluid can crystalise and push the seal out that little bit
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you need to remove the seals in the caliper and clean behind them then install new seals and dust seals had the same problem with my 84 250 some years ago the old brake fluid can crystalise and push the seal out that little bit
ONe of the main causes of gunk in behind the caliper piston seals is RUBBER GREASE, use either brake fluid or buy correct lube from your brake service etc, I think the lube "we" now use is a silicon. The other think to confirm with hydraulics, although maybe not in this case, is the ports in the master cylinder, they can block or/and partially block and restrict the piston ( in the mcyl) returning slightly. One example I saw recently on a modern bike ride was a Kato rider stopping and cracking the caliper nipple and the off he'd go again, lunch stop 70k later and old mate has had one get-off due to ...you guesed it dragging caliper, and now has a bent caliper! quick question over lunch confirmed he fitted new pads "last night", he has also been topping up his master cylinder when ever he thought it was low, didn't remove the added fluid when replacing his pads, you would not believe how far his caliper expanded with the resultant drag (530 kato, chewing twice as much fuel, young blokes with strong right hand.LOL)
kT.
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you need to remove the seals in the caliper and clean behind them then install new seals and dust seals had the same problem with my 84 250 some years ago the old brake fluid can crystalise and push the seal out that little bit
Ok I will go for some new seals.
I guessed they would be ok as they don't leak?
Where did you order the seal kit? Can you get them from Honda?
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There's new seal kits on ebay
http://m.ebay.com.au/itm/150913639199?nav=WATCHING&sbk=1
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id try your local honda dealer first
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There's new seal kits on ebay
http://m.ebay.com.au/itm/150913639199?nav=WATCHING&sbk=1
Man you are quicker on eBay than me(http://)
I also saw a kit with the pistons. That would be the go!
Can you get them in oz? I was thinking maybe ballards ?
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There's new seal kits on ebay
http://m.ebay.com.au/itm/150913639199?nav=WATCHING&sbk=1
Man you are quicker on eBay than me(http://)
That's why my credit card account is in the state it is.
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Thanks for the help gents. Ordered seal kit from Honda today.
Hope to fit it Monday
Thanks again
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when you do the caliper seal make sure you have a very close look inside the groove in the caliper, you'd be amazed how much hidden crap gets in and stays in there and deforms the seal causing drag. AND don't use rubber grease.
Kt
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(http://)
when you do the caliper seal make sure you have a very close look inside the groove in the caliper, you'd be amazed how much hidden crap gets in and stays in there and deforms the seal causing drag. AND don't use rubber grease.
Kt
Thanks for the tip. I appreciate it.
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It won't be the seals in the caliper it will be more likely a warped disc. I have only had 2 instances when the brakes have dragged on my 84 CR's and one was the piston kit in the master cylinder (this will stop the piston from retracting and is a common cause) and if you say you have removed the master cylinder and they are still dragging it will be most likely a warped disc (they turn themselves inside out and curve one way with age, specially if worn) take the disc off and lay it flat on a desk to check this, flip it over and measure the distance of both to the desk to check this. It is hard to pick by eye on the bike and as it is not bend it will not drag as such (like a tight spot) but will be firm as you spin the wheel all round.
The seals in the caliper themselves are pretty bullet proof (I have found anyway) they have a very basic function and are only really a problem if they are leaking.
As usual Only my 2 bobs worth and I have been wrong before but have had several of these bikes as vintage bikes and this is the problems I have incurred.
Shane
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It's Shane's old bike isn't it Paul?
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No Ted it is the 125 I have.
I will double check the disk when I do the seals.
I will be sure to let everyone know.
Thanks also to Shane for the input.
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Thought I recognised the name. Paul all the parts from the 250 fit the 125 so just swap things out till you find the problem.
Sorry Paul which bike did you get off me was it W6?? if so that had the best front disc of all the bikes.
Shane
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Sure was W6 :)
Great bike!!!
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Just a side note to this, we lined up a drag a couple of years back between this bike, my 89 250 and Geoff Mc Mullin's 07 CR 250 and there was only a bike length between all of them up to 5 gear!! them 84 250's (and in particular that bike) go very hard.
Let me know how you get on with the brake issue Paul.
Shane
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So, no excuses now Pauly ;D
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Ok Gents.
I am very pleased to report problem fixed!!!!!
To all those that had input thanks very much.
All those who had money on the seals were correct.
Although the seals didn't leak and did retract, after changing the seals the problem is fixed!!!!
I am pretty sure the trailing piston seal was not as good as the leading one. After removing both they looked different. The trailing one didn't look "tapered" like the new ones.
Thanks to all for the help and offers of assistance!!!