Topic: CB650 Front Brake Master Cylinder Replacement Recommendations

[Adam80]

Hi All,

I'm restoring a '79 CB650 and its mostly complete except for the front brake master cylinder. To buy the assembly as an original part it will cost $953.73 AUD and that's not even including shipping.
 (https://www.cmsnl.com/honda-cb650p-1979-z-general-export_model50281/cylinder-frmas_45500425613/)
Thats right about the amount I paid for the entire bike (welcome to classic motorcycles I know

Anyway I am hoping to get something as a suitable replacement, it doesn't have to look exactly OEM but something similar that's not so expensive if anyone has any suggestions?

Thanks

[fizzlebottom]

https://4into1.com/80s-style-honda-complete-brake-master-cylinder/

I don't have many nice things to say about 4-into-1 anymore, but I bought this for my '82 CB650 several years ago and it has served me well. Hoping that you can get this or an equivalent piece for some reasonable shipping prices.

[scunny]

David Silver spares is the place to go. I got one for my CB650Z a few years ago, cost about $200 landed in NZ.

[pekingduck]

Your CB650 uses a master cylinder with a 1/2" piston, the same size as other single disc '79-'81 Hondas. Many modern single disc bikes feel much more powerful and have a lighter lever pull and better feel. This is due, in part, to a smaller master cylinder diameter, like 10mm, 11mm or 12mm, or 1/2".  The size is usually cast onto the housing body on OEM parts. These might not be suitable for dual-disc though.

Be very careful buying aftermarket brake master cylinders. The one from 4 into 1 has a 5/8" piston, too large for your single disc, resulting in much heavier lever pull and less control.

Look at a new master cylinder from Honda for a 2015 PCX150 scooter.  It uses the same 1/2" piston size and rebuild kits as the new CBR500Rs. You can order replacement parts like levers and brake switches and rebuild kits from Honda. And it retails for under $60.

Don't be concerned that it is off a scooter.  It is every bit as robust as any other one, and it is Honda OEM quality, same as the ones for their CBR500R, except with a silver lever.

[Adam80]

Excellent information thank you guys, they look like great options I'll do some research and see which one to get.

[gearsoup]

I don't have many nice things to say about 4-into-1 anymore..

Why's that? I'm just getting into the CB rebuild hobby, so curious where they've gone off the rails?

[fizzlebottom]

Why's that? I'm just getting into the CB rebuild hobby, so curious where they've gone off the rails?

They just make low quality junk for the most part. I've had their floats fail in a year, wrong fork seals sent, replacement fork seals leak immediately, plastic mirror trim crack after a few weeks, and received damaged carb gaskets.

I know they don't manufacture these parts, but they sure do seem to go for the lowest cost possible, sacrificing quality for quantity. Always prefer OEM where possible, then more reputable manufacturers/sellers like Randakk's, Dennis Kirk, David Silver Spares, Parts N More, etc.

[pekingduck]

Anybody know of new any round, screw-top master cylinders being made?

[Adam80]

Like these?

https://4into1.com/cafe-style-satin-black-master-cylinder-w-clutch-lever-set/

[pekingduck]

That looks pretty good.  It's got a 5/8" piston bore (15.8mm), so okay for dual discs, maybe a bit firm for a single disc.

Looking at more of their master cylinders, and they have a 14mm better suited to single discs.

[scunny]

From memory, but I'm old, my 650z with dual discs ha a 14m master, works well.