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Discussion Starter · #1 ·
So I purchased the stated bike which had been sitting for +20 yrs (put up running and fine with no tinkering done since). It's in great shape and I've replaced some things to get the engine running but I've still got a lingering problem I'm hoping y'all can help me with.
The front brake lever when engaged has ZERO pressure. When I opened the Master Cylinder it was bone dry with a white'ish residue. I wiped it out with some water and towels and cleaned it up. Filled it with a DOT 3 and 4 combination fluid. When attempting to bleed the brakes I am not getting any pressure build up nor am I seeing air bubbles.
I'm sure I'm doing something wrong as this is my first true bike I'm working on. Any advice?

Also can someone post a location to the "banjo bolts" I've read you can bleed the lines through? (there was a topic link but access was denied).

Thank you all for your advice so far
 

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1995 VT1100C2
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Sounds like you need to properly bleed as any air will cause a loss of pressure . Not sure why you combine Dot 3 and 4 so explain that. I am not familiar enough with pre-90 but help will arrive shortly and/or swiftly
 

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Discussion Starter · #3 ·
Sounds like you need to properly bleed as any air will cause a loss of pressure . Not sure why you combine Dot 3 and 4 so explain that. I am not familiar enough with pre-90 but help will arrive shortly and/or swiftly
The DOT 3/4 was a purchase option, bought it from Advance Autos as the rep suggested. Should I drain it and replace with a non combination version?
 

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'83 VT750C; ‘21 SV650A
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The system was bone dry, or close to… So I would imagine the lever was brought right back to the bar when pulled, right? Or the previous owner could have done. In any case, if you are getting ZERO pressure, it’s likely the little plunger, just inside of where the banjo bolt goes into the master cylinder, was overextended and it’s seal inverted. Or worse. I was lucky with mine, where I was able to reach in and tweak the seal mostly back into place, and then seated it by covering the hole with my thumb and pumping the lever to create a vacuum. Try it a few times, but you might have to disassemble it… maybe go so far as using a rebuild kit.
 

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Discussion Starter · #6 ·
The system was bone dry, or close to… So I would imagine the lever was brought right back to the bar when pulled, right? Or the previous owner could have done. In any case, if you are getting ZERO pressure, it’s likely the little plunger, just inside of where the banjo bolt goes into the master cylinder, was overextended and it’s seal inverted. Or worse. I was lucky with mine, where I was able to reach in and tweak the seal mostly back into place, and then seated it by covering the hole with my thumb and pumping the lever to create a vacuum. Try it a few times, but you might have to disassemble it… maybe go so far as using a rebuild kit.
Thanks I'll give that a shot this week and let ya know how it goes.
 

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Repair kit shows still available, Item #14:


You would have to verify the bore is clean with no corrosion/oxidation before ordering. If the bore is bad, look for another master cylinder. Any roughness or pits in the bore will either chew up the new seal or leak by.

Three critical things for a replacement would be bore size the same, handlebar size the same and can you get the banjo bolt holding the hose on connected? (there are universal brake lines available,,,) Integral mirror mount would also be good.
 

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No guarantees on quality, but there are options on ebay:



Edit: the bore size should be stamped in. My 750 Ace has 11 on the side for 11mm bore, My 1100 has 1/2 (12.7mm) bore.
 

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And it might be prudent to open the bleeders down on the calipers, let them drain until clean fluid runs out. button it up and try again. I've had stubborn ones where it took a LOT of messing with it to get pressure. I've had to unmount the caliper and tilt it just right to get the last little air bubble to come out....
 

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1995 VT1100C2
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The DOT 3/4 was a purchase option, bought it from Advance Autos as the rep suggested. Should I drain it and replace with a non combination version?
No need to drain the fluid as 3 and 4 are compatible. I misread your post and thought you were combining the two however I see some suppliers sell a combined 3/4 but not sure why. As of at least 1995 Honda has recommended Dot 4.
 

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1983 Honda vt750 Shadow
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Not a good idea to have water anywhere around brake fluid, but if you get it flushed with new fluid it should be fine. Here is a bleeding trick if you have problems.

 
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No need to drain the fluid as 3 and 4 are compatible. I misread your post and thought you were combining the two however I see some suppliers sell a combined 3/4 but not sure why. As of at least 1995 Honda has recommended Dot 4.
I've never seen dot 3/4 either. It must mean that it's compatible with either so must be dot 4. Dot 4 can be used instead of dot 3 but not vice versa. For a bike that say 20 years i would definitely disassemble and clean master cylinder and the wheel cylinder. Then clean and flush both. If you use water i would thoughly clean and dry all parts before reasonably. Then flush and bench bleed the master cylinder. Make sure to clean all the little holes and passageways. There is probably a little hole in the bottom of the reservoir that must be clear. I learned a lot about this and post it. Check my post from about 2 years ago. Good luck and let us know how it goes.
 

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1983 vt750c in black 25k miles exported to the uk in 2000 non runner since 2009 now resurrected
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Good on ya 👏 I just brought an 83 back from the dead, both clutch and brake reservoir were empty.
I cracked the bleed nipple a tiny amount and had a small length of transparent pipe on the nipple going into a small pot of brake fluid then I just pumped the lever and made sure I didnt run the reservoir dry keeping an eye on that transparent pipe looking for the clean fluid to push the dirty out.

If want to try sucking it through you could use the a carb vacuum stub and run the bike and use the engine to suck it through (old miata trick) using some see transparent pipe just get ready to use the kill switch before it sucks it in the engine.

Mixing brake fluid is normally not a good idea, it oxidises like crazy and we are taught over this side of the pond to only fill from a sealed container, once opened it doesn't last long on the shelf and goes dark quick I think it's dot 5 that is silicone based and doesn't blend well with others and turns into sludge.

Good luck
 

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The original DOT5 is definitely not compatible with DOT 3 or 4. Newer stuff is DOT 5.1 or something. Not sure if its compatible or what the difference is. The DOT5 silicone base works great, but you must dis-assemble all components and remove all traces of the DOT 3/4. Just flushing was not good enough, over the next year I had to replace all 4 wheel cylinders and the master cylinder. then my buggy would roll again. all the components froze up one at a time and I'd have a brake dragging...then m/c not returning...
 
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