Post by new2scootn on Oct 24, 2012 1:57:26 GMT -6
A few days ago I opened a thread asking if anyone knew anything about linked brakes. Due to the limited response I got(only jct842 commented) I'm guessin' not many of you are familiar with them or their operation. Well neither was I but I had to figure out why my front brakes would hang up after applying them with the right brake lever and then would completely release after applying the left brake lever. So I removed the proportioning(?) valve from my Sunny Roadrunner trike to see if I could figure out (a) how the damn thing works! And (b) why the hell it's not workin' right!
Well I'm pretty sure I found the answer to both questions and in the process uncovered a serious and potentially dangerous lack of quality control.
So here's the contraption as it looks on the trike.
Off the trike...
With top jam nut removed revealing spring loaded brass perforated cup(proportioning?)...
A little better detail of that brass cup with it partially removed...
And here with it fully removed. If you look close, you can see the first problem I found.
Beginning to remove the brass fitting...
And wth? is that piece of garbage in the center port?
Ooohhh... it's just a glob of metal shavings from the machining process. No worries having metal shavings/filings and God knows what other kind of crap in your brake lines...(why did I buy Chinese? Oh yeah, I'm cheap AND a glutton for punishment.)
Ok, now we get to the meat of this potato--the main plunger/piston/valve or whatever you want to call it.
I think this one is self explanatory...
Oh look, another clogged port, yay!
So I removed all of this metal shaving garbage, filed off the burrs, cleaned every part thoroughly to remove any foreign material(pun intended), and put it all back together. I haven't had a chance to refill the system and bleed it yet though, but I sure think that these partially clogged ports were the source of my problems. And if I am understanding how this thing works then when the right brake lever is squeazed this will apply ONLY the front brakes. When the left brake lever is applied it will apply the rear brake primarily but depending on how aggressively you're stopping it will also start to push that piston against the spring tension which will force the fluid into the front brake lines and apply the front brakes(just not as hard as the rear brake). The part I understand the least is that spring loaded brass "cup" thing in the fitting where the right brake lever line attaches. Maybe it's a one-way valve? I don't know why but I just like to understand how AND why things work... oh yeah, that's right, it's because I'm cheap and my labor is cheap. And if I understand it I'm more likely to be able to fix it. ;D
Just spent the last four hours refilling the brake fluid in the trike and bleeding the air out only to find that getting all that garbage out of the proportioning valve did absolutely nothing toward fixing the problem with the front brakes hanging up. A bit of harsh language helped to get me refocused.
As I mentioned above I really didn't understand what that brass "cup" things purpose was but now I do... to screw up otherwise normally operating brakes! The more I got to thinking about how these brakes work the more I felt like that "cup" might be the problem. So I figured I'd just remove it and see what happened. What happened was now the brakes work perfectly. Right brake lever operates front brakes only and now releases immediately, and left brake lever applies the rear brake and then the fronts with increased pressure. So the "cup" and the spring were a type of one-way valve only needed in the head of whoever the engineer was that the Chinese copied it from!
Oh yeah, speaking of extra parts, guess what the UPS man dropped off today? My new fuel tank has finally arrived!(LOL!)
Sure glad I haven't been down for the count in the mean time! Biggest surprise is that the new fuel tank came with a cap, drain bolt, AND a brand new level sensor! Never expected that--figured if it was free it would be ONLY the part I needed. Definitely gonna bag and tag it and file it for future reference!
Well I'm pretty sure I found the answer to both questions and in the process uncovered a serious and potentially dangerous lack of quality control.
So here's the contraption as it looks on the trike.
Off the trike...
With top jam nut removed revealing spring loaded brass perforated cup(proportioning?)...
A little better detail of that brass cup with it partially removed...
And here with it fully removed. If you look close, you can see the first problem I found.
Beginning to remove the brass fitting...
And wth? is that piece of garbage in the center port?
Ooohhh... it's just a glob of metal shavings from the machining process. No worries having metal shavings/filings and God knows what other kind of crap in your brake lines...(why did I buy Chinese? Oh yeah, I'm cheap AND a glutton for punishment.)
Ok, now we get to the meat of this potato--the main plunger/piston/valve or whatever you want to call it.
I think this one is self explanatory...
Oh look, another clogged port, yay!
So I removed all of this metal shaving garbage, filed off the burrs, cleaned every part thoroughly to remove any foreign material(pun intended), and put it all back together. I haven't had a chance to refill the system and bleed it yet though, but I sure think that these partially clogged ports were the source of my problems. And if I am understanding how this thing works then when the right brake lever is squeazed this will apply ONLY the front brakes. When the left brake lever is applied it will apply the rear brake primarily but depending on how aggressively you're stopping it will also start to push that piston against the spring tension which will force the fluid into the front brake lines and apply the front brakes(just not as hard as the rear brake). The part I understand the least is that spring loaded brass "cup" thing in the fitting where the right brake lever line attaches. Maybe it's a one-way valve? I don't know why but I just like to understand how AND why things work... oh yeah, that's right, it's because I'm cheap and my labor is cheap. And if I understand it I'm more likely to be able to fix it. ;D
Just spent the last four hours refilling the brake fluid in the trike and bleeding the air out only to find that getting all that garbage out of the proportioning valve did absolutely nothing toward fixing the problem with the front brakes hanging up. A bit of harsh language helped to get me refocused.
As I mentioned above I really didn't understand what that brass "cup" things purpose was but now I do... to screw up otherwise normally operating brakes! The more I got to thinking about how these brakes work the more I felt like that "cup" might be the problem. So I figured I'd just remove it and see what happened. What happened was now the brakes work perfectly. Right brake lever operates front brakes only and now releases immediately, and left brake lever applies the rear brake and then the fronts with increased pressure. So the "cup" and the spring were a type of one-way valve only needed in the head of whoever the engineer was that the Chinese copied it from!Oh yeah, speaking of extra parts, guess what the UPS man dropped off today? My new fuel tank has finally arrived!(LOL!)
Sure glad I haven't been down for the count in the mean time! Biggest surprise is that the new fuel tank came with a cap, drain bolt, AND a brand new level sensor! Never expected that--figured if it was free it would be ONLY the part I needed. Definitely gonna bag and tag it and file it for future reference!
