Clutch master cylinder nightmare

[Gsxjohn]

Gents,  I've changed the brake and clutch hoses on my bike. The front brake was a nightmare to bleed. I'm doing the clutch now and the sod won't bleed. I've fitted new seals etc in master cylinder but now noticed that when I pull the lever the piston in the master cylinder doesnt return leaving play on the brake lever, I've stripped it a couple of times now and checked for obstructions in the cylinder, all seems ok. If I push the piston manually before fitting it works ok.
Any pearls of wisdom would be great🤞👍

[Hooli]

The clutch slave won't return when it's not fitted. There is a spring in there that holds the piston out, so it is always pressed against the pushrod. Have you refitted & tried?

I've never had a problem bleeding the clutch, indeed I've stripped, cleaned & refitted mine within 45mins when it decided to leak one morning before work.

The front brakes however are an utter twat when dry, I always fill them from the bleed nipple with a syringe of brake fluid. It makes a four hour job into a 30min one.

[Gsxjohn]

Hooli, it might be my description. It's the master cylinder piston that's not returning. With the reservoir cap off you can see the piston through the feed hole in the reservoir. The slave cylinder is fitted on the bike so is pushed in.

Know what you mean, the front were sods, ended up taking the banjos off the calipers and getting the lines filled that was.

[Hooli]

Ahh I get you now.

No idea sorry, never had my master cylinders apart. Never needed too.

[Andre]

I had a buildup of some solid hard crud where the seals go. Would have caused the seals to stick out a bit more than they should. Did you check for that? Only other thing I can think of are the seals themselves: are they the correct ones (i.e. "bad" brand).

[KiwiCol]

Have a look in the GSX1400 Manual - Part 1, Section 6, page 55.  (Download section, under Manuals) Shows the striped down master, might want to check that spring.

[Gsxjohn]

Cheers guys, I'll  have another strip down and double check in the morning. 👍👍

[Gsxjohn]

Well I stripped the master cylinder again today. Made sure everything was smooth in the bore of the cylinder, re-assembled and the flaming thing works....nothing different done from before.  Only issue  now is the clutch is dragging so I'll  bleed it again.
Can't complain really, the bikes been sitting  for 2yrs.

[Eric GSX1400K3]

Heres a tip re bleeding thats always worked for me: when nearly done, i.e new fluid coming out of the lowest point, crack the nipple open so you get flow, but before the lever touches the bar, close the nipple by hand, and with the other hand on the lever you should feel resistance.  Let the lever out again and repeat, this forces air to the lower nipple.  If you close the lower nipple  AFTER  releasing the lever, the vaccum created by the master cylinder sucks air in via the thread at the lower nipple, undoing what youve just tried to do.  If you leave the system for 10-20 min after refilling, this can make it easier too.  Keep an eye on the resevoir, you can also get air trapped in behind the master cylinder and bore that takes a while to pump out.

[Gsxjohn]

Cheers Eric, I'll  give that a try👍

[GSXKING]

I borrowed a mates vacuum operated brake bleeder and it sucks the old fluid through. Then you put the new fluid in and draw it thru until it comes out the bottom nipple. No air bubbles what so ever and really good feel through the lever. 

[Dusty ST]

I borrowed a mates vacuum operated brake bleeder and it sucks the old fluid through. Then you put the new fluid in and draw it thru until it comes out the bottom nipple. No air bubbles what so ever and really good feel through the lever. 

I did the same at the weekend with my new clutch slave cylinder, I'd also renewed the hose, so also filling an empty system.
I find the vacuum bleeder gets the fluid through, but I still need to manually pump fluid through as I can never be sure the bubbles I'm seeing with the vacuum are the bleed nipple connection sucking air in.

[Hooli]

I borrowed a mates vacuum operated brake bleeder and it sucks the old fluid through. Then you put the new fluid in and draw it thru until it comes out the bottom nipple. No air bubbles what so ever and really good feel through the lever. 

For those of us without toys you can do the same with a syringe.

I still prefer to fill from the bottom though, after all air floats so it pushes it the way it wants to go.

[VladTepes]

Jeez Hooli, why are you so anti gravity ?   

[Notty]

Jeez Hooli, why are you so anti gravity ?   

Gravity is there other way up here clearly