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I have that problem now. I use a 4.5 inch tube to push and hold the brake pedal down. When I start the ride, the brake is much improved, but after 50 miles it goes down down down.
 
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I have that problem now. I use a 4.5 inch tube to push and hold the brake pedal down. When I start the ride, the brake is much improved, but after 50 miles it goes down down down.
I believe the Rune has a linked braking system which requires you to bleed the front brakes as well as the back. The front calipers have 3 pistons the center piston activated when applying the back brake. I believe the order to bleed them in is front L front Rt then rear see attachment
 

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Thank you RUNE517!! This procedure has always alluded me until your last post. They say a picture is worth a thousand words and now I know the high point you鈥檙e referring to. Totally doable.
-Ollie
 
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Hi.
What I am about to say may not be all that helpful but perhaps give an insight into what may be a source of the problem. I purchased my Rune earlier this year. It was courier delivered to my home.
I found the back brake did not work at all !!
Having found there to be no brake fluid in the reservoir I removed the master cylinder off the from the bike and stripped it down. It was internally bone dry, not even damp, no evidence of brake fluid in there at all.
So at this point I'm thinking the back brake has never been operational. Hmmm.
It is a strange affair internally and to me this complexity will lend itself to blead back and possible air ingress. I didn't take a pisture of this assembly and now realise it would have been helpful. In appearance it is not unlike the the hydraulic flutings found in a hydraulic steering rack. Here is where I think the gremlin may be. Unlike a hydraulic sterering rack there is no preloaded fluid pressure created by a pump. A clue here is that a steering rack is designed to self purge and does so with because the hydraulic fluid is pressurised, I'm sure most of us have bled a steering rack so I won't get into this. It is this very aspect of the master cylinder design I believe may be the underlying problem; No fuid preload at rest. I have yet to reassess the brake and re-bleed the system to appraise the situation but the fluid level is, as filled by me. I believe the master cylinder is allowing a certain amount of leak back internally and since the seals are at their most effective when under pressure and since the system is pulled back by spring force a certain amount of negative pressure will theoretically be created internally. This theoretical internal vacuum may be enough to draw air past unstressed ( technically loose ) seals and into the master cylinder - just a thought and not impossible since a remedy written in this forum, having some pedal preload at rest supports the theory.
I will say though if my imaginative theory is correct then Honda need to issue a recall.
Regarding assembly, there appears to be an adjustable threaded rod linking the foot pedal to the master cylinder. Except it doesnt adjust, or it didnt appear to be designed to be adjusted with efforts to do so by myself leading me to conclude this. I have to say at this point I didnt have the workshop manual so did this job without reference.
In summary to the master cylinder all seals appeared in good nick but there was a small amount of dry and dusty residue of something inside the master cylinder. I cleaned everything, reassembled it and bled it. The system is the same as for a VTX ( I got one of these and have experience of doing this particular job ). It is, in my opinion very straight forward to bleed it. I got a firm brake pedal with sharp brake actuation and authority.
Roll on a month or so and it doesn't seem quite so firm, though I am bearing in mind I haven't ridden the bike on the road owing to needing a new front tyre yet.
I'm not particularly concerned about the brake pedal unless braking efficiency deteriorates then I will look for a permanent solution.

All the best
Howard
 

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I have pretty definitive evidence that the rear master cylinder is NOT the problem, and that the problem is as 517 states: The high point of the linked brakes trapping air. Here's why I say this: The chopper that I built uses all of the same OEM components for the rear brake as the stock Rune. The pedal is always firm, and has never had the spongy issue. The difference: My chopper does NOT have linked brakes.
 

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What I find interesting about this scenario is. I can bleed the rear system from the rear reservoir through to the rear caliper only, and get a sharp responsive pedal. Much better than my VTX in fact. Then after a month or so the travel has increased with a slightly softer pedal being felt under foot (I've noticed it does raise and firm slightly with a single pump).
I'm wondering how this situation exists, if air already existed in the high point ( identified in your photo ) and the brake pedal, master cylinder and rear reservoir part of the system is linked as one with the front then the good pedal would never exist having bled the rear only, surely ?
I'm thinking along the lines of brake pressure control regulators on other vehicles when a full brake pipe replacement situation has been performed. You can push fluid through the system all day long, until the PCR is bled. Once bled the brake pedal becomes authoritative and remains so unless a failure in the system occurs. This I fully understand as all wheels are operated in what is essentially a combined system ( for the purposes of this discussion ). So if air is bled out of the system thoroughly, the brake pedal should not falter as it does unless air is somehow getting in to the system. If it is fully combined then bleeding the rear only should not give me a good pedal. This forms the basis of my thinking.
Are you saying that once this identified area of the system is bled then integrity will remain thereafter ?
I wish I could get Allen Millyard (a remarkable chap) to cast an eye on the issue. Sadly he's rather elusive.

Kind regards
Howard
 

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As 517 points out; the high point of the system for the rear brake is the junction block just in front of the fuel tank, on the frame neck.
I believe that once that trapped air is removed, the system integrity will be maintained IF: you install the float that is present in the handlebar master cylinder. As Rune517 postulates, that float stops air from mixing into the fluid from acceleration/deceleration forces, and should have been installed from the factory.
 

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I didn't know there was not a float in there. That's pretty grim, I see exactly where 517 is coming from on this point. Assuming I don't have said float where and how or from what other bike has a chance of fitting it ?
Thanks
Howard
 

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Hi Howard,
I鈥檓 not too sure of what you鈥檙e asking in your last question, but 517 outlines the procedure fully in the #1 post and shows the part number of the float you鈥檒l need to purchase and place into the rear master cylinder. Hope that helps.
-Ollie
 
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Hi Dr Dave, do you know how to turn thr DRLs off at the front I seem to recall something about using the dipped beam switch with something else?
I'm still working on the floats for the resrvoirs, my job has got in the way these past few days but hopefully I can do the work you guys have recommended amnd give you some feedback.
Thank you for bearing with me on my imaginitive theories.

Howard
 
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