Bleeding of a motorcycle braking system

[MV Owner]

Dear All,

Firstly, I am a newbie here so a big hello and please be gentle!!

My inquiry needs expertise from someone who could help a motorcycle enthusiast on the art of brake system bleeding on a motorcycle.

The motorcycle is an italian MV Agusta F4 and is fitted with a radial type master cylinder with one single braided line from the master cylinder down to a rigid metal line with splitter mounted above the front mudguard that feeds two six piston calipers on stainless discs. There is no bleed nipple on the master cylinder and each caliper has only one bleed nipple.

I have purchased some 'speedbleeder' one way bleed nipples. These weren't cheap and cheerful items, but are a very tightly fitting nipple in the caliper body thread so I would suggest there is no scope for air getting drawn up the bleed nipple threads on the brake lever release stroke (if this is in fact possible or maybe I'm talking nonsense).

My usual method of bleeding is not to 'reverse bleed' the system from the bottom up (like some others do) but to apply a soft rubber hose to the bleed nipples and open the nipple and pump the master cylinder slowly and rely on the ball bearing arrangement in the speedbleeder to flush the fluid through the system until I see no bubbles. I use around 1 litre of fluid for a system which I would suggest is around 250ml in capacity.

I would appreciate your expertise on a number of issues please:-

1. Some MV Agusta owners remove the calipers prior to bleeding and push the pistons back into the caliper body so when the system is being bled there is less fluid in the system. They then top up the reservoir as the fluid drains in the first 'piston movement' application. I would appreciate your thoughts on the validity of such a suggestion.

2. Should I bleed the caliper 'furthest away' from the master cylinder or does it not matter?

3. Should the bleed nipples be opened the 'standard' 90 degree turn or open the nipple the slightest amount so the fluid is forced out of the bleed nipple under a 'harder' pressure from a slightly stiffer brake lever.

4. What are your thoughts on whether a 'Mity Vac' vacum pump applied to the nipple produces a better end result of whether it is in fact just a tool that aids the process.

5. Should I ever slightly open the banjo where the brake line connects to the master cylinder to remove any in the master cylinder? If this is suggested, should I perform this at the beginning or end of the bleeding process.

6. The bleed nipple on the MV brake calipers is mounted quite high up on the caliper body. Therefore some would suggest that the oil below the nipple (all six pistons) would never be bled from the system as the new oil will simply pass down the brake line and out through the nipple (as opposed to mixing behind the piston then out through the nipple). Does this seem a reasonable concern? If so how is this fluid below the nipple best removed

7 Should the squeezing of the lever be slow or fast during the bleeding process. Does fast squeezing promote the temporary compression of bubbles in the liquid?

8. Is there any value in gently holding the brake lever back to the bar overnight? If so should the reservoir cap be removed or would this promote the contamination of fluid with air.

I would be very thankful for your assistance.

Kind Regards





MV Owner

[mzivtins]

Hi MV Owner,

what a very special bike you have, could you please post some pictures of your bike? For all the members who aren't familiar with the MV Agusta f series of bikes, the exhausts and nose make draws drop!

1: This is the best thing to do, clean the exposed pistons with the relevant cleaner before re-seating the pistons as far back as they will go. This helps bleed calipers as, like you said, less oil in the system = less air to remove = firmer brakes.

2: The order shouldn't matter too much, but you must not only bleed the caliper, you also need to bleed the master cylinder too as this is the highest point in the system and where most air bubbles will collect.

3: So long as fluid is coming out of the nipple, you are doing it correctly, the less of an opening, the better.

4: see below

5: Yes you should also bleed the banjo connectors of the hoses, this is the only way to bleed the master cylinder connection. Bleeding nipple and banjo lines will give you one -finger brakes.

6: see below

7: see below

8: Leave the cap off will allow water ingestion. there is no need to pull the lever back, this was more of an old trick for crap master cylinders and calipers. Normally the next day, any air bubbles that failed to move would have collected in place where a quick bleeding will rid these.

The Mighty-Vac is the best tool for the job, with this you can achieve perfect brakes.

Pump the lever slowly using the full range of motion possible. Be sure to watch the reservoir to make sure it doesn't become empty and suck in loads of air!

The benefit of these brembo's is in the design, the bleed nipple being at the highest point possible is a PRO rather than CON.

The internal pathway of the fluid travels behind the pistons prior to the reaching the bleed nipple, pushing fluid through (bleeding) will push the air all the way to the bleed nipple. Most other designs, like cheaper Tokiko calipers are much more difficult to bleed due to their bleed nipples.

It is worth bleeding the next day, ever so slightly, and maybe even a day after that, you will find you brakes get better and better this way.

hope this helps

[MV Owner]

Dear MZ,

Thanks for the post, I'd be more than happy to post some links to my bike-

http://gallery.mvagusta.net/submariner/photo/37214/

http://gallery.mvagusta.net/submariner/photo/37230/

http://gallery.mvagusta.net/submariner/photo/37234/

Thanks for all your advice MV, Im going to consider this and come back with any more questions. Thank you very much. If any others can chip in please do!!!

[MV Owner]

One more thing MZ, the master cylinder I have has no bleed nipple. I assume I can bleed the master cylinder by loosening the banjo nut, squeezing the lever then re-tightening the nut?? If I should do this, should I do it at the beginning or end of the process

[mzivtins]

One more thing MZ, the master cylinder I have has no bleed nipple. I assume I can bleed the master cylinder by loosening the banjo nut, squeezing the lever then re-tightening the nut?? If I should do this, should I do it at the beginning or end of the process

Do it last it is messy so stuff rags everywhere as you dont want that fluid over your beautiful machine!

[mzivtins]

For easy viewing, this is the picture posted:



Probably the best looking exhaust system seen on a vehicle stunning

[bdr529]

One more thing MZ, the master cylinder I have has no bleed nipple. I assume I can bleed the master cylinder by loosening the banjo nut, squeezing the lever then re-tightening the nut?? If I should do this, should I do it at the beginning or end of the process

Do it last it is messy so stuff rags everywhere as you dont want that fluid over your beautiful machine!

Good advice
break fluid will cause damage to your paint finish, even with the new clear coats that are used these days.
cover the gas tank, don't get it on your rims or tires, and don't use the gas tank as a shelve to hold the bottle,
take it from me, your just asking for trouble

[MV Owner]

Many thanks gents,

I have always been careful when it comes to the hazards of brake fluid. I use a large syringe with tube to fill the maaster cylinder to avoid any spills.

Any other tips on how the remove bubbles would of course be very greatly welcomed

[strad]

The only thing I can add would be to agree with this : """It is worth bleeding the next day, ever so slightly, and maybe even a day after that"""
There are microscopic bubbles that cling to the inside of the brake line and it can take a day or two for them to coalesce into a larger bubble . The brakes might feel fine at first but after time all those teeny tiny bubbles get pushed together.

[J.A.W.]

Rather than go to that level of hassle,
I'd suggest you try a period of pressuring the system, by pulling the brake lever on via a cable-tie, say - overnight.
The constant pressure will tend to force out any residual air.

[godlameroso]

Make sure the bleeder is pointing straight up. Then just gravity bleed. Then zip tie your break 'pedals' tight, leave it overnight. Pull the break light fuse so you don't drain the battery. Enjoy the most firm breaking you've ever had.

This technique also works with your clutch slave cylinder. You should syringe the fluid out of your reservoirs every other month, and replace it with fresh fluid. Good ol' ATE typ 200 is my fluid of choice, before that it was the ATE super blue.

[J.A.W.]

For easy viewing, this is the picture posted:

http://gallery.mvagusta.net/image_db/su ... /37230.jpg

Probably the best looking exhaust system seen on a vehicle stunning

4 boring black tubes poking out from under a tailpiece?

Nah, I don't think so.. check out an X-75 Hurricane http://www.realclassic.co.uk/bikepix/hu ... 011403.jpg

Or even more 'technical' - yet aesthetic - see an unfaired Honda NSR 500 GP bike..
http://powersports.honda.com/images/v4/ ... 500_BO.jpg

[strad]

once again we are at odds.. I personally think the X-75 kinda gross but to each his own I guess.
Your love affair with Kawasaki is showing.

[J.A.W.]

once again we are at odds.. I personally think the X-75 kinda gross but to each his own I guess.
Your love affair with Kawasaki is showing.

Strad, FYI..

The quoted reference was about appreciation of the aesthetic presentation of a technical object, viz: exhaust system.

X-75 is an original factory custom/cruiser/chopper, based on an American re-style of a BSA..
The Honda is a GP 500 race bike.
So, the contrast is between style for art's sake, & the stylistic merit of pure race-tech.

But no mention of any Kawasaki at all, so why raise your issue of a "love affair" with them, unless you have an example to present?

[strad]

You're right...jumping to conclusions.
My first thought was that it was yet another picture of you're beloved H2
+1 for J.A.W.