Morini 125 Front brake master cylinder?????????

[themoudie]

Assistance please

Stripped out the front brake master cylinder on Morini the Minx today. All came apart smoothly, the plunger coming out with the sealing 'O' ring slack and the 'wiper' 'O' ring looking like just an 'O' ring, whilst the return spring had broken where it attaches to the plunger!

Cleaned all the old **** out of the cylinder bore, flushed with brake cleaner, checked for scoring etc. all looks clean. Lubricated the bore with clean brake fluid, then lubricated the seals and plunger with clean fluid. Inserted the plunger spring first and gently eased the 'wiper' 'O' ring into the bore. Then the sealing ring met the top of the bore and the piston will not go in any further!!!

I have removed the piston, added more fluid for lubrication and tried again with same result. I don't wish to use 'force' to 'pop' the sealing ring into the bore if I'm tearing the 'wiper' seal inside the bore.

Am I being a woose? My thoughts at present are to line it all up, lubricate, then clamp in the vice and gently wind the piston in. Putting the lever in place to hold the whole thing together could prove a colourfull Saturday night's entertainment!

I look forward to reading a suggestion or two and if you read this SteveL, does #1 have a definitive reply?

My thanks, Bill.

[guest146]

Hi
do you have any pictures of the working of this.

Ken

[guest146]

Thinking about this,you should get some rubber grease as this will help a lot more than brake fluid. Be carefull with the lip on the seal as they are quiet fragile. If you could find something thin enough you could make a type of funnel to ease it in but it must not be Sharpe and would need to be very thin.

ken

[Jez F]

 I had the same problem on a Brembo master cylinder on my Guzzi. I got a tool made up in aluminium to the specs in the official Guzzi manual, basically a sort of hollow punch which eased the seal in. It's hiding in the depths of the chaos which masquerades as a garage at the moment, but I will try to dig it out and check the dimensions, but I think yours is a Grimeca so will probably be different diameter , but should put you onto the right track.
Cheers Jez

[themoudie]

Good evening to you kerabo and JezF,

Thank you for your contributions, my evening has not been as colourful as I feared and with a bit of 'Classic' radio on the go I'm surprisingly chilled!

Returned to contemplate the offending plunger again and then realised that the adjuster in the lever is in fact a long grub screw with a hex drive in the end and a nut over the end as a lock nut. Not centre dotted on as a cheapskate bolt!

So put the plunger in with some more fluid, then put the small rod in [having 'Armourall'd the wee bellows to keep them supple] with a touch of molyslip, backed off the adjuster, lined up the pivot hole in the lever and popped in the pivot and locked it up. So far so good. Gripped the mounting studs of the resevoir in the vice then using the adjuster grub screw on the lever applied gentle  pressure to the plunger, all appeared to go well, so having adjusted the grub screw and nut then applied pressure with the lever and eased the seal with a shaped 'Magnum' ice cream stick and in it popped! Will have to wait now until I've removed the 'toffee' from the rest of the system and have it all re-assembled on the bike to see if I've made a right Horlicks of it, or not!

Time will tell.

JezF, I like the sound of the hollow punch with a taper to ease it all in, but not sure if there is the room to fit all that round the hole and then fit the lever whilst resisting the return springs urge to fling the contents of the cylinder across the garage. I suspect you'd want to spit, violently!

My thanks again, regards to you all and have a good nights kip, Bill.