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Rear master cylinder source?

Posted: Tue May 16, 2017 4:59 pm
by icouldabeenav8
My '79 rear master cylinder still oozes despite rebuild attempts. Is there a source for new ones? I notice cheap Chinese ones available for other models but not for 1979.

Re: Rear master cylinder source?

Posted: Wed May 17, 2017 11:20 am
by steve murdoch icoa #5322
I was surprised to see different numbers when i looked at a parts fiche but the other years will work on your '79.
Once again i think it was Nils that looking into getting the cylinders bored.

Re: Rear master cylinder source?

Posted: Wed May 17, 2017 5:34 pm
by FalldownPhil
I believe you are correct Steve.
Best,
Phil

Re: Rear master cylinder source?

Posted: Thu May 18, 2017 4:26 pm
by icouldabeenav8
Thanks, buying a cheapo ebay master cylinder - will report back.

Re: Rear master cylinder source?

Posted: Fri Jul 07, 2017 4:44 pm
by icouldabeenav8
Well, my cheapo eBay master cylinder experiment is at an end. Theoretically it would work, but after solving one fitment issue after another I decided the work was too much effort. I took another look at my old m/c to see if I could determine why it was leaking before making the final dive into modifying the new one.

Upon disassembly, I found nothing wrong with the new rubber parts. There was nothing wrong with the cylinder bore. Hm-m-m-m. I looked at my near 40-year old original rubber parts I had removed. The old stuff had no cuts, tears, rips etc., so I decided to reinstall my original OEM rubber parts.

After 24-hours , no leaks and the master cylinder is working perfectly! It may yet leak, but at this point, the m/c is vastly better than it was with the new guts. I am sure that Zeus is laughing just waiting for me to relax. :handgestures-fingerscrossed: :handgestures-fingerscrossed: :handgestures-fingerscrossed: :handgestures-fingerscrossed: :handgestures-fingerscrossed:

Re: Rear master cylinder source?

Posted: Sat Jul 08, 2017 10:59 am
by Mouse
The new rubber parts are theoretically identical to the old rubber parts but in reality they are a few thousandths smaller hence they leak. Happens all the time for me with repairing my older pickup truck. I solved the frustration by upgrading everything I repair. :-)

Re: Rear master cylinder source?

Posted: Mon Jul 10, 2017 8:34 am
by daves79x
Rebuild kits for the original M/C s are still available from Honda.

Dave

Re: Rear master cylinder source?

Posted: Wed Jul 26, 2017 4:39 pm
by icouldabeenav8
Still holding.

Re: Rear master cylinder source?

Posted: Fri Jul 28, 2017 8:17 pm
by CopperCollar
A long shot here but in the past I was able to use the rear master cylinder off a Honda dirt bike. Close as I could tell it was the same as the CBX one but the actuation shaft was different. I was able to use the CBX actuation shaft and the master cylinder was a direct bolt on.

It's been a long time and I no longer have the part number but I think it was to one of the dual purpose bikes.

I am thinking the master cylinder may be the same across the product line with only the actuator rod dictating the part number difference?

Re: Rear master cylinder source?

Posted: Sat Aug 05, 2017 2:12 pm
by NobleHops
Re this resleeving topic, I did have my front MC re-sleeved several years ago by a place called Apple Hydraulics in New York. It worked perfectly, and has ever since, was $100 or so as I recall. They were exceedingly careless with it though, nicks and gouges were all over it when I got it back. Would not use them again.

Re: Rear master cylinder source?

Posted: Sat Dec 30, 2017 5:44 pm
by icouldabeenav8
Still holding. Success declared.

Re: Rear master cylinder source?

Posted: Mon Jan 29, 2018 2:49 pm
by Caley-Thistle
I had the same problem and bought a new rear master cylinder from Aliexpress for £10. All I had to do was drill the master cylinder top mounting hole to 8mm and tap the bottom one to 8mm. Works a treat.

Re: Rear master cylinder source?

Posted: Wed Feb 28, 2018 2:59 pm
by hondaman160mph
I came across this information in the 2018 March/April issue of Motorcycle Classics magazine.
Brake and Equipment Warehouse (brakeandequipment.com) in Minneapolis Minnesota will bore out your pitted front or rear master cylinder
and press in a stainless sleeve and hone the inner diameter to OEM dimensions.