Bleeding linked brakes, 99 Bassa HELP! (solved!)

[Michael_A]

I think I made a bit of a mess of things and need some advise.
Went to bleed the brakes.
The front was easy; handlebar master and right caliper. No issues.
The rears... Were working OK, but fluid was very dirty.

Bled the rear caliper fairly straightforward using the pedal/open & close the bleed screw. Got old fluid out. Went to the front and tried the same. No flow using the pedal. Attempted reverse bleeding the front and can confirm fluid back into the rear reservoir. Thought all was good, pressed on the pedal and the feeling went from fairly firm suddenly to dead soft. Oh my. No leaks present.
Reverse bled front and rear calipers. Confirm fluid flow up to reservoir. Pedal maybe a touch firmer but still goes to the bottom.
Tried bleeding from the top of the rear master. Get flow on the down-stroke, close banjo, repeat. Messy, but can confirm fluid pumping out of that, so I presume the master is still able to make pressure.
Pedal a tiny bit better, but still not right.

Frustrated and feeling like I'm beating my head against the wall. Factory repair manuals are kind of worthless on this matter.
I have gear to both reverse pressure bleed and of course vacuum bleed. Tried all variations and no significant improvement.
Anybody have a decent "how to" that can be followed?  I guess I could try bleeding from the banjos at the "block" assembly - a high point sortof behind the battery, but am hesitant to make things worse.
Saw in the parts diagram some kind of "brake correction device" and am now worried I may have somehow screwed that up, though I can't even locate it on the bike at the moment!
Again, any insights, tips, or advise welcome.

[marcmorrison]

Mike..sorry to hear the brake bleed job has hit an obstacle....as you know from my worksheet, it has been about 7 years ago since I bled the brakes, so I'm not surprised you found some less than ideal colored brake fluid.  As I recall, I used the tried and true pump, open/close the bleed screw method until all was good, but seems like I may have finally resorted to just a plain, simple gravity bleed to finish the job (or maybe I'm confused with one of the other machines I worked on at about the same time??).  I noticed the hand brake was a little spongy before you picked up the bike....the brake resevoir was low on fluid, but it didn't look so low as to require bleeding the master cylinder....I added some DOT4  to get it back to the correct level.  You might investigate the possibility that the master needs to be bled before going to the calipers??  My only suggestion for now, but I'm sure others will chime in on the subject.

[guzzisteve]

Make sure the caliper is higher than the master, may get all sponginess out of front.

[Michael_A]

Hey Marc!
I think I may have gotten it. A combination of reverse pressure bleeding, the old fashioned "up/up & down down", and lots of cussing. The pedals downward stroke was limited by hitting the chrome frame trim. Removed and readjusted the pedal and it gets full travel now on the downstroke - a partial stroke may have been part of the issue. I'm not familiar enough with this bike to have a feel for what's "normal", but the pedal (and hence the linked brakes) are building and holding pressure, not "pumping up" from soft, but may be a bit longer travel than what I am used to (could be "normal). I'll take it for a ride and see. The linked brakes are kind of a weird item so that compounds trying to establish "normal"!

[marcmorrison]

Try adding in some adult beverages...can't hurt!!

[Michael_A]

Gentlemen, I have achieved VICTORY!!!
After trying almost every bleeding tool in the shop, I took a break, had a stiff drink, and remembered I have an industrial compressed air fluid evacuation system for industrial bleeding!
This thing can pull almost a complete vacuum, and suck about a gallon of brake fluid through a system in about a minute. What the heck, lets try it on the rear. Sucked about a quart through the rear and you could see the air bubbles getting entrained and sucked out. Topped up the master and was was rewarded with a rock hard peddle! About 1/2 inch slack, then nice and hard. Should have broke that tool out earlier!
Well, the good news is the bike got a massive hydraulic system flush! Both front brakes and rear linked brakes rock hard!

[marcmorrison]

Hooray...now get out and ride it

[Michael_A]

Definitely looking forward to getting it back on the road! Almost all the recommissioning service is done. Your maintenance over the years (and records) certainly paid off! Dropped the sump to change the filter and the bottom end was spotless. No grit, metal shavings, or anything. The worst part was scraping off the old pan gasket. Valves were (surprisingly) very loose (better than tight). Only real squaks found are some engine breather hoses (crankcase to frame and frame to airbox) that have cracked with age, kind of a pain to get to but everything is stripped down so now is the time and quite a few "mud dobber" insect nests, the kind that make mud "homes" in things. Big ones on the throttle body plate, top of engine, and under the bike on the hydraulic compensating valve (actually jammed it up, cleaned and freed up the mechanism, working fine now). Dumped out all the old gas and replace the tank to pump hose. That one looked original so it was due. The remaining high pressure hoses look recent and fine. All in all, very sound and I can't thank you enough for the conscientious record keeping and saving all the take-offs. The one bag marked "I have no idea" actually contained all the hardware and plastic plugs needed for removing the highway pegs off the lower crash bar attach point. Need to clean up my shop and lift, give the bike a good detail, and hopefully take it for a shake-down ride this weekend, BTW, title and registration stuff done at DMV yesterday. Thanks again, Marc!

[guzzisteve]

I use one hooked to air compressor, new calipers on the CARC's & even yours have smaller holes than older Tonti's. Well done. At least you can stop.

[chuck peterson]

Mark E at Moto Uzzi Classics did a video on this

His technique includes taking the mcylinder off the frame and rocking it clockwise and anti clockwise while pumping

Air bubbles get stuck inside

Video via his fbook feed

Glad you got it! A gallon of brake fluid?!?!

[Michael_A]

Maybe closer to a quart or so.. Maybe a bit more. Earlier failed attempts expended a lot of that. The final big vacuum bleed went through maybe 150cc's before I got the air out and the peddle back (the big vacuum bleeder is pretty high performing, and COULD suck a gallon in about a minute, but I didn't go through that much! Did have to monitor the fluid levels closely during the operation and continually top-up). It had been a while since the brake fluid was really flushed out, so this exercise pretty much took care of that - a bit of a silver lining I suppose. Problem was it made a mess on my lift so I need to pause and do a big clean up!

[chuck peterson]

You should be getting a little 1/2” of fluid popping up like a fountain out of the mc’s when it’s right

[Michael_A]

Now that I got the system working I did some investigation as to where things went off-track that I thought I'd share for the "next guy"...

Front brake (right side): bleed as normal, no real issues at all. On the Cali EV with the pull back handlebars the M/C rests at a pretty acute angle. You almost have to "overfill" slightly so the level doesn't "unport" and thus suck air when turning the bars. Other than that observation, the right front is pretty straightforward.

Left front: Your NOT going to be able to bleed it using the peddle! There is a pressure relief/regulating valve that send fluid to the front brakes only under certain pressure levels that are not going to be reached during bleeding. Normal for the linked system. It is best to reverse bleed the left front, as the return is not restricted by this valve. You are on your own as far as making sure your reverse bleed rig doesn't introduce air or make a mess during this procedure. Lots of advice out there (teflon tape the bleed screws, etc...).

Rear Master: Here is where things went south for me initially... The RESERVOIR'S supply hole at the bottom is slightly LOWER than the inlet for the rear M/C! They are connected by a hose, hence the "elevation difference". I completely drained mine to clean out some muck in the bottom. This likely caused the rear M/C to "back drain" and introduce air into the system, unbeknownst to me at the time. Reverse bleeding pushed SOME of the air out, but it's a pretty convoluted brake line routing that holds air bubbles easily. A "Mighty Vac" or syringe reverse bleed only jiggles the bubbles back and forth. Using my high capacity vacuum extractor suck so much fluid through so fast it entrained the air and got it finally out of the system.