77 cb750f2 Master cylinder questions and great deal on braided lines.

[Matt Story]

First the great deal.  There is a outfit on Ebay from Ontario Making custom braided steel brake lines to order.  You can spec exactly what you want for ends, bent or straight banjos threaded... fitting rotation and color.  They want $23US plus shipping per line which after looking around for a considerable while was the cheapest I could find.  I bought a full set of 4 for my 77 cb750f for $106 including shipping.  The Ebay sale looks as if its for a specific bike, but once you buy it you can specify exactly how you want them made regardless of the sales advertising.

The link for the ebay seller is: http://stores.ebay.com/coastguard1975?_trksid=p4340.l2563

Now for the technical...

I am currently redoing a brake system that was clogged in a garage for who knows how long.  My front M/C was fairly corroded.  It cleaned up nicely, but I'm not sure how big the tiny hole on the bottom of the reservoir is supposed to be.  The bigger (2mm?) hole is wide open, but can just barely see light thru the small hole.  Can someone help me with a reference for how big the hole is supposed to be?

On the rear M/C I also bought a rebuild kit.  I opted to buy the one made for 75' & 76' bikes because it looked identical to the  '77 version plus a ball stud for the linkage and a check valve.  There are pics of the differences here here  All the other parts are the same.

I am not sure to use the check valve or not.  There wasn't one in my M/C when I took it apart.  The check valve comes with the 75'-76' kit and not with the 77' kit.  Did they take it out by design or just stop supplying it in the rebuild kit?  Depending on which exploded view you look at some show a valve some don't.  None of the pictures I have match my later split reservoir - M/C.  Further, all the draiwngs I have for the front M/C include a check valve - this, although there was not one included in the rebuild (77' version) or one in my M/C when I took it apart.  Makes me wonder about the front too.

Are the check valves necessary, or a benefit?Maybe I'd be better off without them??  Any advice?

Thanks,
 Matt

[Matt Story]

I did a lot of searching and I have the small hole in the master cylinder worked out.  Going to open it up with a guitar string or 1/64" drill bit.

I still don't know what to do about the check valves in the MC's.  See my debacle above.  Anybody have some advice there?

Thanks

Matt

[Matt Story]

Yesterday morning I went down to the local repair shop and asked my questions.  The owner/mechanic looked up my assemblies on his micro-fiche and to;d me that I didn't ,need the check valves on my machine.

Also talked to him about the relief hole in the master cylinder.  Didn't learn much there.  I solved this one by some trial and error.  First I got a small piece of copper wire strand to go thru the hole.  I then chased the hole with a 1/64" drill bit and pinvise.  I didn't see any aluminum shavings, and the hole is clean thru now.  I searched high and low for a dimensional spec for this small hole, and didn't find anything.  I am going to go out on a limb here and state 1/64".  If anything, I think that is a hair smaller than the actual hole so it should be safe.

Matt

[shinyribs]

I'm trying to figure out the check valve thing. What is it checking,can you tell? I know the rear m/c on the earlier bikes had an integrated fluid reservoir . Do the later model have a remote reservoir? Maybe that is the difference. Just a thought...

Rear master off my 76F

[Matt Story]

I am still not certain I have it right.  Yes, my '77 has a separate reservoir connected with a hose.  The pictures I have specific to my model don't show a check valve, and one didn't come with the rebuild kits.  I went to the local shop to see what their mechanic thought.  He brought the same pictures up that I had and came to the conclusion that I did not need them.  I have them re-assembled, and am waiting for some caliper parts to finish the project.  I'm going to try them w/o the check valves.  I will report how it turns out.  Should be no problem

By the way, my braided lines came in just as I had specified (very slightly longer than requested) and look like they will fit perfectly.  They are bolted up waiting for the caliper parts.

Matt

[Piute]

       
                                       SURE IS  like my ugly pic.

[shinyribs]

The only time I have ever known a check valve to be in a brake system is if the fluid reservoir is mounted at a point in the frame where it could become lower than the caliper. e.g.- going up or down hills. Reason for it is that it keeps the fluid from draining back into the reservoir from the caliper,creating a need to pump-pump-pump to get a pressured pedal.