Can't stop a front brake piston from leaking

Hi, I've recently overhauled the brakes on my '99 SV (s). Back brake is fine (new seals, cleaned calipers, new pads, new rotor). Front left is good as well (new pads, rotor and seals), but for front right I needed to replace seals and one of the pistons. I got it from WeMoto (Worlds end motorcycles?). The piston went in too easily first go, then I realised that the seals that came with the piston were different to the originals. I tried the new seals with the new piston - much better but it is still leaking when I apply the brake.
Has anyone else had problems with pattern parts for brake pistons - Should I go get Suzuki low quality, hight cost, but proper spec parts?
Any help or advice greatly appreciated.

[yorkie_chris]

Is the piston installed correctly? It's kinda possible to nip the seal as you install the piston.
You need to pull it to bits and see what's going on. Sounds like you have the wrong seal tbh. I've found wemoto's returns dept. to be pretty good though.

[Dave20046]

out of interest what does the brake lever feel like with a leaky piston?
Mine still isn't perfect and I'm starting to suspect a leaky piston

[yorkie_chris]

Creeps back to the bar if you hold it on. Depends how bad the leak is.

The big question... can you see fluid appearing around the pistons.

[TSM]

take it all apart, check that all the seals are in good condition

are you sure its leaking from the pistons or is it possable that the bleed nipple is closed properly or the main banjo is leaking?

[Dave20046]

Originally Posted by yorkie_chris

Creeps back to the bar if you hold it on. Depends how bad the leak is.

The big question... can you see fluid appearing around the pistons.

I can see it protruding then looking to disappear when i squeeze and release the lever, thought that might have just been excess/moisture being drawn around by the piston movement - but it doesn't creep back to the bar.
Just a tiny bit spongey but it won't bleed up.

[yorkie_chris]

So there's fluid around the pistons? Did you put it there when installing pistons (as recommended by haynes, but actually a really daft idea...)

Your brakes are leaking elsewhere though aren't they? This would explain sponginess.

[Dave20046]

Originally Posted by yorkie_chris

So there's fluid around the pistons? Did you put it there when installing pistons (as recommended by haynes, but actually a really daft idea...)

Your brakes are leaking elsewhere though aren't they? This would explain sponginess.

Yeah I did dip them in brakefluid if I remember (oops), with a lack of rubber grease I assumed it was better than nothing.
New mastercylinder, new lines. Could it just be air, still...somehow

<grin> not sure whose thread this is anymore ... but still ... Yes, I'm sure it is leaking from the pistons - I checked the bleed nipple and banjo and they are dry as a bone.
My brake feels normal as I pull the lever back. but after holding it for a few seconds it gives a little, and there is brake fluid on the back of the pads nearest the pistons (and some dripping off the bottom of the caliper.
I used a very small amount of brake fluid to lubricate the pistons, far less than has leaked out (enough to drip off the pads!).
I checked the seals - all looks good, no nicks or twists.
I do seem to have had a lot of trouble with Wemoto -both the front and rear rotor bolts they sent were the wrong ones! Has anyone out there ever used the Wemoto pattern pistons?
thanks for the useful suggstions so far!

[TSM]

Originally Posted by Dave20046

Yeah I did dip them in brakefluid if I remember (oops), with a lack of rubber grease I assumed it was better than nothing.
New mastercylinder, new lines. Could it just be air, still...somehow

you know the white cristaline stuff thats around the seals when you service them, thats what happens to brakefluid when its in contact with the air

use red rubber grease