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Discussion Starter #1
Ok, way back when I bought a used radial master cylinder off a wrecked 636 from a guy on here. I bought the 636 Galfer SS lines and did the conversion this past weekend. Without having the slightest clue as to what I was doing I figured it couldn't be that damn hard to remove lines and fluid, replace lines and fluid, and get the air out. After spending about an eternity trying to bleed the lines at the calipers and master cylinder nipple I discovered that the master cylinder nipple wasn't getting a good seat and was sucking air while I used the mightyvac hand pump.:BangHead: A couple wraps of teflon tape later (not blocking the flow hole) I got a good seal out of the nipple. I got pressure at the lever and decided to take her out for a spin. Initial bite wasn't overly impressive but anything after that was good. Rode it home and back over to a friends house the next day with no problems. We decided to take a ride and after getting about two miles from his house we got on a straight away. We had to slow behind a truck and I used the front brakes minimally until we could pass. Once we got around him I opened it up to about 120. As I let off I could tell the front was dipping. Long story short, my calipers locked up on my rotors so tight I couldn't roll the bike in neutral. :suicide: WHAT HAPPENED?! I let the bike sit on the side of the road for about 15 minutes to cool off and when I got back on it the bike could roll in neutral. I rode it home using only the back brake. What do you guys think could be the problem? Is the master cylinder malfunctioning or is there something else I'm overlooking?:dontknow: Keep in mind the master cylinder came off a wrecked 636 that caused the brake lever to bend. I replaced the lever with a new one but could there be something internal in the master cylinder that is binding not allowing the pressure to relieve in the lines? Any help would be greatly appreciated! I got a race school coming up August 20th and would like to have all this sorted out well in advance.:thumbsup:
 

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Discussion Starter #2
:pale: Wow! 24 hours later and no one on here has taken a shot at this one. If it's that bad I must be facked!
 

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Possible that the teflon got to the internals somehow and blocked the flow of hydro fluid. Or in the wreck the cylinder/plunger that is connected to the lever may have been damaged. Does the lever move freely when it's not on the bike? How clean are the pistons in the caliper? If they're dirty they could bind up in their bores- take the calipers off and remove the pistons, clean em up, check the piston seals for debris or extreme wear, gently clean seals/or replace, reinstall cylinders. There's only a few moving parts in the front brake system- the piston in the master,and the pistons in the calipers. Each of them has replaceable seals/ rubber parts that can wear out. Did your system work fine before the upgrade? Make absolutely sure there is no teflon tape obstructing the vale openings!!
 

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Possible that the teflon got to the internals somehow and blocked the flow of hydro fluid. Or in the wreck the cylinder/plunger that is connected to the lever may have been damaged. Does the lever move freely when it's not on the bike? How clean are the pistons in the caliper? If they're dirty they could bind up in their bores- take the calipers off and remove the pistons, clean em up, check the piston seals for debris or extreme wear, gently clean seals/or replace, reinstall cylinders. There's only a few moving parts in the front brake system- the piston in the master,and the pistons in the calipers. Each of them has replaceable seals/ rubber parts that can wear out. Did your system work fine before the upgrade? Make absolutely sure there is no teflon tape obstructing the vale openings!!

:+1: Sounds like a problem down at the pad where the heat is produced. Obviously if it cooled off and worked something that is effected by heat caused the lock up. Glad it didn't lock up at speed!!!!
 

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Possible that the teflon got to the internals somehow and blocked the flow of hydro fluid. Or in the wreck the cylinder/plunger that is connected to the lever may have been damaged. Does the lever move freely when it's not on the bike? How clean are the pistons in the caliper? If they're dirty they could bind up in their bores- take the calipers off and remove the pistons, clean em up, check the piston seals for debris or extreme wear, gently clean seals/or replace, reinstall cylinders. There's only a few moving parts in the front brake system- the piston in the master,and the pistons in the calipers. Each of them has replaceable seals/ rubber parts that can wear out. Did your system work fine before the upgrade? Make absolutely sure there is no teflon tape obstructing the vale openings!!
i would suspect the caliper pistons, dirt, debris, crud around them & seals not allowing the pistons to retract properly.
Another member here had seeping fluid issues from the bleed nipple on the 6r MC and wanted to use teflon tape but everyone that replied suggested not to(including myself) as the threads are not the seal but rather the tapered end of the bleed nipple when it seats into the MC as they are machined to do exactly that, seal. Oh and yes bits of teflon can get into the system and create havoc so please remove it.

BD
 

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This Happened to my dad on his 96 Royal Star also only at around 80mph!
I rebuilt the m/c and bled all the old fluid out,reassembled,and they work great now. After inspecting,i found that the Vale hole in the return was clogged with a shaving of sum sort.But this bike also had sit for a long time when we bought it.
 

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Look for twisted lines, they can act as a one way valve if they are pinched, you can squeeze pressure past them but it wont return,locking up your calipers.

Teflon tape shouldnt be used on brake bleeders as stated above, the taper on the bleeder nipple should be the seal in the dish at the bottom of the threaded hole.
 

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Discussion Starter #8
Thanks a ton on the info guys! I'll check and execute all of your recommendations. On a side note, the entire brake system worked like a champ before I started this (what was supposed to be little) project.
 
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