The front master cylinder on my V50ii is enormous and I have found a smaller one which is compatible. I have never bled a linked system before - is there anything I should be aware of before taking the plunge?
TIA
Hey @Welshguzzi1 - a couple of things here. on the subject of bleeding linked brakes, generally, hopefully someone accomplished at that art will be along very soon - but it would be good to clarify what you are bleeding: you’ve (also) mentioned the front cylinder and that usually only governs the front-right of the system (the foot brake usually handles the ‘linked’ bit: front left and rear).
With regard to the ‘master cylinder’ you need to be cautious about changing these: as standard they are spec’d to handle the single front-right. if someone has, in the past, ‘de-linked’ they may have fitted a different spec m-cyl (to handle two front discs). To get the best possible help, you’d do well to more fully describe the bike’s current setup and your intent. hth!
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Hi Barry - thanks for your reply.
The front and rear brakes are still linked. The current front M/C is definitely non-standard and doesn’t work very well as there is so little movement on the lever. I managed to get a replacement from Pete Morcombe who assured me that it would be compatible. As the 2 front discs are on separate systems, I wanted to check that it was just the normal procedure to change the single disc side, but also I’m going to bleed the linked system at the same time so wanted to see if there was anything I needed to be aware of (sorry - forgot to mention this bit in the OP)
that’s good extra info - cheers. Guzzis, especially older Guzzis, can be far from ‘standard’ so it really helps to know what you are working with (o:
so: front master cylinder - Pete Morcombe knows his way around Guzzis, so you’re surely sorted there. Wonder why it was changed? Maybe just ‘failed’ and a P.O. just used what they had.
Again, hope a bleeding expert is along soon because there are various tips, from ‘pushing’ new fluid in (with a big syringe and a bit of hose attached to a bleed point), to ‘pulling’ with a vacuum pump. The simple approach is to get a third hand*, and work methodically: front to back or vice versa (some ‘splitters’ have a bleed nipple too, so check for that. Some owners swear by clamping the brake lever down overnight, others in (unbolting and) raising the calipers above the level of the (rear) m/cyl.
not an expert here - on my linked brakes T3 a mate used a vacuum pump to bleed mine. what a revelation. also what a rate the new fluid pulls through at!
*third hand? master cylinder is one side, bleed nipples are the other, so mate + tea/beer
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Of my rusty experience: I bled linked system once, and more accidentally than deliberately. I mean, I wanted to do that, but somehow new fluid didn’t want to go through, and then finally did - how, why - I can’t remember. But it wasn’t straightforward, despite splitter doesn’t seem to be anything complicated. For that reason I think a vacuum pump is worth considering. Re front m/c, this is counterintuitive really: the smaller the piston, the more effective brake, of course within certain limits. So, later models have 1/2 in piston(12.7mm) on the handlebar, while foot m/c uses 5/8in(15.8mm). And if we use anything like 14mm or 15 on the handlebar for single pot, the feel is so wooden. I went 11mm and this was revelation, comparing to previous state. Don’t forget to tell us about the outcome!
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The bike was an insurance write-off (presumably too expensive to repair), so I’m guessing was fixed with whatever bits were available - good enough to pass the MOT…
I think I’ll see if I can get hold of a vacuum pump - I had similar issues with my Ducati Bevel - it was an absolute sod to bleed particularly when starting from empty. And that didn’t even have a linked system!!
I also started using a vacuum pump recently they are not expensive and do the job quickly. It is easier if you have a second person topping up the master cylinder reservoir as you pull the fluid from the caliper end very quickly. If the reservoir empties, then you are back to the start as it will pull air into the system.
As for bleeding the front master cylinder, that is nothing to do with the link system. It just serves the front right disc.
The linked system connects the foot brake to the front left and rear disc. I start bleeding with the splitter unit, then the front and finally the rear.
The brakes often feel soft after bleeding. Pumping the pedal usually resolves that.
Be carefull with the bleed nipples, they are fine and can shear off if you are heavy handed. If they feel stiff to undo, try warming the caliper a bit.
Thanks Don, all useful info. Would this work? I usually avoid cheap tools but I’ll probably only ever use it a few times https://www.amazon.co.uk/Ambienceo-Vacuum-Bleeder-Adapter-Automotive/dp/B08ML3Q6BX/ref=asc_df_B08ML3Q6BX/?tag=googshopuk-21&linkCode=df0&hvadid=499333735334&hvpos=&hvnetw=g&hvrand=8941846181834487540&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9045371&hvtargid=pla-1131987988490&psc=1
I use exactly that and it does the job.
That looks the same as the one I use. Cheap, but actually quite effective.
What about auto bleed valves - the sprung ball bearing type. Slaken off and pump away till fresh comes out, retighten valve - all done no mates or juggling needed. You can do it with one hand and a beer in the other hand
Not sure if I am allowed to mention brands…
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Remember that the piston in the M/C needs to be fully returned to the lever with play in-between to allow fluid through the orifice and into the chamber.
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Quick update: front M/C replaced - what a difference! Haven’t had the time to bleed the linked system yet…
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