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Discussion Starter #1
Hello everyone,

When taking my SV650 03 out after 6 months of winter storage, I found to my surprise that the rear brake no longer works. The brake pedal pushes all the way to the bottom without any resistance and the brake doesn't take at all. It worked fine when I put the bike in storage. There has been no leaks and the rear reservoir is still full. The brake is of the single disc type.

Has something happened to the master cylinder? If so, will I need to replace it or is it repairable?

Any help will be much appreciated!

Roger
 
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Rear Master Cylinder

Afternoon RogerDahl and welcome to the forum.

Sounds like to me there might of been some moisture present in the Brake Fluid (especially true of Dot 3 and 4 which easily absorbs moisture compared to Silicone-based Dot 5) and it got into the Rear Master Cylinder's Piston / Plunger Ring - possibly seizing it into the grove so it no longer is able to provide a seal between it and the cylinder. So when you depress the brake pedal, poof - no resistance... the fluid just goes past the Piston in the Brake cylinder. You can either replace (safest bet) the Master Cylinder or rebuild it, your choice. Then flush out the system with completely fresh Brake Fluid. Assuming I'm correct on this I'd say IF there was so much moisture in the rear cylinder then odds are good the front is just as bad. For peace of mind either do it or have it done, change the front Brake Fluid as well.

LRG :cool:
 

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Discussion Starter #3
Hello LowRiderGhost,

Thank you for both the welcome and for taking the time to reply. What you're saying sounds very likely as I have been negligent in replacing the brake fluid. I will attempt to rebuild the master cylinder. Found a how-to online and it doesn't look too hard. I also found a few recommendations for a piece of equipment called the "Mighty Vac" for flushing the brake fluid so I'll get one of those as well and do both the front and rear brakes. I'll post a followup message on this thread once I've attempted the repair.

Thanks again for your help!

Roger
 
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Dot 3/4 is a pain BUT.....

Hey Partner, definitely DON'T beat yourself up over this, ok?! :D Who the heck of us out in the 'real world' would be checking this?! Mind you when I get a used anything it's among the first things I check. Again Harleys are not such a problem because they've been using DOT 5 (Silicone) since I'm guessing the 70's. But the Victory I got last year is using Dot 4.... was there a bit of rust in it? You betca'! :rolleyes: I don't know if your (?) Susie is using Dot 5 or (most likely) Dot 3-4. If the later is true I'd recommend starting with a fresh (sealed) can. Afterwards putting the can in a zipper baggie and squeeze the air out of it, then keep in house (not garage). This will cut down even the fresh stuff from getting contaminated (absorbing moisture from the air) quickly!

LRG :cool:
 
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