Brake Master Cylinder

[nicomasala]

Hi All,

Apologies if this has been covered, i did try a search and couldn't see what i needed.

Im having some issues with the front brakes on my 1987 VMAX 1200, It all started when the brake lever would stick in when pulled. The brakes were bled to prevent the lever travelling to the point where it would stick.

I have stripped the master to rebuild it to try and sort this problem, but after replacing the parts in the order they came out, i get fluid leaking back through the rubber boot over the end of the piston.

Having gone through user manuals etc, i cannot find the correct way to install the parts, and in which direction the seals should face.

One seal had to be stretched over the first plate of the shaft, and doesn't look like it sits right now.
Does anyone have pictures etc of how the rebuild kit should be fitted up.

Im happy to post pictures for inspection if that helps.

thanks

Nick

 

[dannymax]

Haynes manual Chapter 7 http://www.besit.ru/vmax/HSRM/chap07.pdf

Page 8

Seals are cupped so they push fluid towards the banjo end of the master.

There's a clear diagram showing this.

'87? Where are you from? :ummm:

 

[Jan Bee]

Haynes manual Chapter 7 http://www.besit.ru/vmax/HSRM/chap07.pdf

Page 8

Seals are cupped so they push fluid towards the banjo end of the master.

There's a clear diagram showing this.

'87? Where are you from? :ummm:

Martock is in England.

 

[nicomasala]

Hi,

Thanks both for the replies.

I have the Haynes Manual, and fitted the seals with the open end facing the Banjo bolt as per the image (without sliding the last seal over the wide part of the shaft. When refitted and the lever pumped it would flow no fluid. i could remove the banjo and squeeze the lever and nothing would come out. Im just lost with it, as feel i have tried them in every position and option and no luck.

Martock, Somerset, South West England.

thanks

Nick

 

[nicomasala]

Heres an image if that makes it cleare.

 

[nicomasala]

That is how the old parts came out

 

[MaxMidnight]

Have you checked that the hole that goes from the reservoir to the m/c bore is clear?
Can we assume that you have checked that there isn't any scoring on the m/c bore?
Have you tried reverse bleeding or a Mitivac?

 

[nicomasala]

Hi Steve,

I forgot to mention, that when the MC was first rebuild using the parts in the same order as the picture, it would bleed with pressure and then all of a sudden release a bunch of bubbles into the MC reservoir and you would loose feeling at the lever.

Both the feed and return holes are clear. I will double check the bore for scoring, but couldn't see anything obvious.

Cheers

Nick

 

[MaxMidnight]

That would suggest that the seals are (were) in the correct way but you have an air leak elsewhere or there is still some air in the system.

Can we assume that you replaced the copper washers and that all of the mating faces are clean and free of dents and dings?

If you don't have new washers the current ones can be re-softened (annealed) by heating them to cherry red and then dropping into cold water.

If not already tried I would use the reverse bleeding method as it is easier to displace the air upwards than it is down.

 

[nicomasala]

Ok Thanks Steve.

We did replace the copper washers, and all surfaces seemed clear.

We replaced the parts correctly (As per photos) again after, and still had no luck.

I dont have the kit to reverse bleed, so may need to hand it over to the bike shop

Nick

 

[MaxMidnight]

Nick - YGM