Topic: Master cylinder rebuild question for CB500K

[KentTaylor]

I'm rebuilding the master cylinder (MC) on my CB500K.  I bought a rebuild kit which came with no instructions or diagrams.  The first diagram here is the diagram in the CB500K repair manual.
My question is this; Is #8  the "Secondary cup" installed as shown between #7 and #9 or, is it installed as shown in the second diagram; onto #7?

[brooze72]

That's a fine question, my guess would be "if" the seal in question has a hole in it, I think the second diagram would apply, (eg: shaft thru hole in seal) but my own question is why do you have two different diagrams for this bike? 

Also, did you make note of how it was assembled during the tear down?  My 500 K manual is like your first diagram, soo.. I think maybe we need Dave500 or TwoTired to give a definitive answer as to what is going on here.

[KentTaylor]

Brooze72
The second diagram is one that I've generated (with the help of Photoshop) to clarify my question.  Only the first diagram came from the Honda repair manual.  As far as disassemble goes, there wasn't much to take note of; the piston, remnants of the spring and a bunch of rusty goo.  The seal (#8 secondary cup) does have a hole in it, and it does fit nicely over the piston.

[brooze72]

Well I may be wrong, and I haven't ever rebuilt mine, but I think you have fixed a flaw in the manual, IMO 

[Kevin400F]

The bottom diagram correctly depicts how it should be assembled.

Kevin

[crazypj]

You have to stretch the hell out of it and 'carefully' ( )
 fit into the 'slot' about halfway along piston rod
(I didn't look at the diagrams  )

[dave500]

bottom picture is how it should look with the red seal on,the top one sort of shows it in sequence of removal.,where that seal lives on the piston there is a ridge ring,inside the seal there is a groove for it to settle into.,part #9 the main cup has no hole and just backs up to the petal valve on the pistons end.

[brooze72]

Well Kent, I think that settles it, the "OldTimers" have spoken and your modified drawing is correct (nice job on that, by the way).

Now we have to figure out how to get the corrected drawing into our posted Honda service manual, part 3 chassis, page 70.  Is this a job for the moderators? Do we have a procedure to submit updates or corrections to the info on our site?

[KentTaylor]

Thanks to all for your input!  My gut instinct was that the second digram was correct but I did'nt want to be wrong and ruin this seal.  That would mean $36 for another rebuild kit and a couple of weeks waiting on it.
If anyone needs it, here is the revised diagram without the Secondary Cup highlighted; it will print out better this way.

[OneWheelDrive]

I know it's been a long time since the last reply, but this is valuable advice.  After having rebuilt my MC just like the actual diagram depicts, then looking closely at the crusty one I removed, I realized that I totally blew it.  I then had to struggle with that damn snap ring again in order to disassemble then reassemble it correctly.  Great job Kent with the photoshop revision of the manual!  I won't make THAT mistake again.