Hello.

Any tips for re-fitting calliper pistons without wrecking the seals? (first attempt at this has ended up with one calliper leaking from the seal [under brake pressure] - pretty sure it was the brutal manner of re-fitting the piston that has done for the seal(s) - 25+yr old rubber style piston seems awfully tight compared to the alloy ones I've worked on before - wonder - do they swell with age?].

Thanks in advance.

SR

You need to clean the callipers , clean the seals , beter to use new ones . Lube the seals with red rubber grease and light smear on the piston . It will push in with thumb pressure . Make sure you are pushing them square .

You have to make sure it is wet before you put it in

The seals may well swell with age, but also the recesses that the seals sit in get crap deposited in them so the seals stick out more than they should. This makes the fit too tight and stops the pistons going back in.

You need to clean out those recesses, and really get new seals, for the sake of a few quid it's madness to not replace them whilst you've got the calipers apart.

Also, give the pistons a good rub with fine wet/dry or wire-wool to get rid of any deposits/corrosion.

Do this and they will work like new.

Good luck.

Al.
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Cheers....

Al

Bikes:
GPZ900
NC30
NSR250SE
RGV250 vj22

Thanks lads - the seals I wrecked were new! Used rubber grease too. Everything was scrupulously clean. Pistons certainly wouldn't push in with MY thumb pressure - had to use a G-clamp! As said, the pistons are not alloy - but rubber - Something I've not seen before (it's an MC16). Was wondering if the pistons swell with age - making refitting more troublesome than I'm used to?

I thought they should be steel ?

Iv'e seen some pistons made of a hard black material, that resembles something that looks like plastic or bakerlite, ( if anyones old enough to remember bakerlite ), not that iv'e specificly seen it on NSR's, but certainly on varios bikes over the years, so would imagine thats what they are. Still dont help you though!!!.
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Proud Father of , 05 ktm 400exc supermoto 2018 honda crf rx supermoto

Just so's you don't think I've gone mental.................

i have never worked on mc16 brakes so i am not sure if those are standard . Now that it has been mentioned , i too have seen those black brake pistons . I thought they were a fibre composite . Sorry but thats all i know .

Can you push the pistons into the callipers without the seals in place ?

Neal - got 2 MC16's - both with same pistons - so guess they are prolly OEM. Good point about checking how tight hey are without seals - I'll give that a go - any meaningful resistance prolly means I aught to be looking at new ones

Anyone know if there's alloy / steel pistons that'll fit the MC16 standard calliper?

ta in advance

SR

As far as I know, they are the same as VFR400 (NC21), CBR400 (NC19 and 23), and many other small capacity Hondas of that era, and I believe all have plastic pistons.

I find it hard to believe they would swell, and more likely that, as Al says, it's muck and/or corrosion in behind the seal (in the goove).

If you have used aftermarket seals, there is a (small) possibility you have been supplied the incorrect ones, or that maybe they are not quite the same size as OEM.

As Neal says, the pistons should press in easily by hand.
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Andy.
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Did you have any luck yet ? Do the pistons push in with out the seals ?

Get's worse - on removing the calliper - one of the pad-hanger pins is totally seized-in. Tried an impact gun - shagged the 5mm allen (hex) socket in the process. It's recessed into the calliper - so couldn't think of any other way of removing other than drilling - it seems to be some sort of chrome-molly. Bloody hard. 20mins of drilling for an inch of progress. Be lucky to get it out without knackering the threads on the calliper - thought about using a (reverse-threaded) stud-extractor - but last time I used one on an an alloy calliper - it split the calliper in two! Looks like I might be after a new calliper in a day or two - anyone got one for sale (RHS)? know which other models it was used on (searching for honda mc16 on 3bay doesn't yield much you see!)

Thanks in advance.

grrrrrrrrr

SR