Honda CBX Master Cylinder Repair

| 12/6/2017 12:00:00 AM

Keith's Garage


Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Q:  I’m working on a restoration and need to repair the master cylinder on this bike. The problem is the bike has been sitting since 2002, and the brake fluid is likely original. The bores are corroded and will probably not seal properly. Do you know anyone that can “bore” the plunger holes and fit an oversize plunger and seals? Any information will be helpful, thanks.
John Montes/via email

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A:   If you have the cylinder bored, you’ll want to have it sleeved back to the original size. Increasing the bore size of the master cylinder will reduce the effectiveness of the hydraulic brake. There are sleeve kits available for several British bikes that reduce the bore size to increase the braking, but I don’t know of any companies offering this service for Hondas.


11/17/2017 10:39:49 AM

Master Cylinders and Brake Cylinders aren’t so much like engine Cylinders . Often you can clean them up enough with a brake cylinder hone, and maybe need to replace the caliper piston if it is really pitted. As mentioned in there is no "oversize piston" but usually the new rubbers fit snugly in the honed out cylinder. I suggest you try honing the bore(s) first and see if they will clean up... Also consider buying a new master cylinder if available, many different "clone" Honda master cylinders are available on eBay.

11/12/2017 3:30:27 PM

Thanks to our helpful readers, we now have two options for metric master cylinder re-sleeving, and I'm sure there are more. Floyd Webb wrote to recommend White Post Restorations at and Earl Johnson recommends Brake & Equipment Warehouse at 455 Harrison St NE, Minneapolis, MN 55413 1-612-375-3141 Thanks to both of them for helping to fill the gaps in my knowledge.