'73 RD350 Master cylinder - Tiny Hole

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EEEliminator
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Joined: Tue Jun 07, 2016 2:45 am

'73 RD350 Master cylinder - Tiny Hole

#1 Post by EEEliminator » Thu Jul 28, 2016 11:14 pm

I'm rebuilding a master cylinder for a '73 RD350, brake fluid was all jelled inside the reservoir... it was bad. I got it fairly well cleaned out and I've been trying to clear this little tiny hole out that supposedly releases the pressure when you release the handle. I cannot get a sewing needle through this hole it is so small, I've tried blowing out with a rubber tipped blow gun at 130 psi and no luck.

I read you can use a guitar string, I tried this but I cannot get the string to clear the hole out. Some say you can cut the string on a 45 and spin it like a drill, not working for me. I also tried grabbing it close to the hole with some needle nose to keep it from bending and tried to push it through and tried soaking with carb cleaner.

At this point I've almost convinced myself that the hole does not go all the way through, except I can see it though the bore...

Does this hole really effect the functioning of the brakes? I know its there for a reason...

Here is what it looks like:

Image

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JonW
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Re: '73 RD350 Master cylinder - Tiny Hole

#2 Post by JonW » Fri Jul 29, 2016 12:32 am

it will have a function if its there. is it drillable with a very small drill? someone had to make it, if its blocked it needs unblocking... can you pul the guitar string in a drill and run it in there?
80 XT500 Supermoto!
81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
85 RZ350 F1 Resto
86 RZ350 F2 Resto
86 RZ350 F2 Hybrid

Like Watches? www.PloProf.com & www.DeskDivers.com

EEEliminator
Posts: 4
Joined: Tue Jun 07, 2016 2:45 am

Re: '73 RD350 Master cylinder - Tiny Hole

#3 Post by EEEliminator » Fri Jul 29, 2016 3:25 am

JonW wrote:it will have a function if its there. is it drillable with a very small drill? someone had to make it, if its blocked it needs unblocking... can you pul the guitar string in a drill and run it in there?
I think it is too small for a drill bit, I did get the guitar string into to the chuck of the drill. I had to sandwich it between a bit and the chuck since when the chuck is closed in all the way there is still a gap in the center larger than the string. This made the guitar string off center of rotation, but since it is flexible and with a little extra length I was able to hold it centered in the hole. It eventually got through!!!

So now on to cleaning up the rest of the body and repainting before re-assembly!!!

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JonW
Posts: 10599
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Location: Sydney
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Re: '73 RD350 Master cylinder - Tiny Hole

#4 Post by JonW » Fri Jul 29, 2016 11:02 am

cool, glad that worked.
80 XT500 Supermoto!
81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
85 RZ350 F1 Resto
86 RZ350 F2 Resto
86 RZ350 F2 Hybrid

Like Watches? www.PloProf.com & www.DeskDivers.com

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