Cr 84 hydraulic brake drag

[Paul552]

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

[Hoony]

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.

[Paul552]

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?

[evo550]

Is the caliper floating properly ?

[kdx Geoff]

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.

[Paul552]

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?

[GMC]

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.

[Paul552]

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 ?

[kdx Geoff]

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.

[Paul552]

Alright I will check by cracking the nipple

Thanks

[Nathan S]

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.

[Paul552]

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.

[crs-and-rms]

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

[Ktm181]

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.

[Paul552]

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?