Master cylinder Question

So I'm thinking about replacing my seized mc with this one i found online. http://cgi.ebay.com/ebaymotors/Front-Brake-Master-Cylinder-Honda-CB400-92-98-/160635516915?pt=Motorcycles_Parts_Accessories&hash=item25669f77f3#ht_5683wt_948
It says it's for a 92-98 cb400, I have a 74 cb360. I just want to make sure I'm not throwing my money away if I get it. It's not much more than the cost of a rebuild kit so if this will work I think it's worth my money yea? Any way I'm a total newbie to this so please help me out. I have read on here that it's the piston size that matters, but I can't seem to find the piston size on this model, but I am guessing if it's for a cb400, there is a good shot this would work. Help me out, what do you guys think?

i can't find that model so i can't check the bore. it may be a u.s. model so perhaps someone else will chime in with what the bore is on that. the stock bore is 14mm so any master with that bore should work. a smaller bore master *may* not move enough fluid to properly actuate the caliper and a larger bore may not have much 'feel' to it, but i'm not sure it's as sensitive as some people say. if the bore on that was 12.7 or 15 i bet it would still work. i used a 12.7 with my CB360 front end and it seems perfect:


this vendor has other cheap masters as well http://cgi.ebay.com/ebaymotors/FRONT-BRAKE-MASTER-CYLINDER-XS400-XJ600-SECA-SRX600-/120770490445?pt=Motorcycles_Parts_Accessories&hash=item1c1e7b704d

things to think of when getting a replacement master that you tend to forget about are the orientation of the hole for the banjo bolt, whether you need a brake light switch, a hole for the mirror, and just the overall size. if you're running stock bars you've probably got some room to play with. some of us with clipons need a more compact unit. but yah, i've heard horror stories about rebuilding masters and if it's seized, the bore will probably need to be honed before you rebuild it... unless you have a hone already adding that to the price of the rebuild kit is gonna get you more than the cost of one of these masters like you're looking at so i'd say go for it. like i said, i'm totally happy with my 12.7mm bore with the CB360 caliper.

Dude thanks that's great. I will shoot them an email and ask for the bore size. I am running clipons and hoping to use my stock switches. I'll see what they say. Thanks again dude I appreciate it

alright so i dont know if i did a good thing or a bad thing here but, my stock MC was totally seized, so i poured some CLR onto the piston and let it sit. after about 20 minutes i checked it again, and it was working great i put the lever back on it has full motion and springs back. my only concern is now i probably have to rebuild it right? or at least take it all apart and clean it with brake cleaner before i try and use it? or can i just bolt it back on and run some brake fluid and see if it works?

Yes it must be stripped and rebuilt. You would still be better of with a new replacement if you find one the correct bore

K good to know

well i am just gonna get the same one you got thats 12.7, since i know yours works, its really gonna be the cheapest option for me. did you use the brake light switch on the lever or did you run it through the same stock cb360 tree mount switch? i have clipons so i am probably going to get the braided line set. anything else special you had to do to get this MC on your cb360?

For size comparisons check the caliper piston diameter and cruise on over to Vintage Brake

http://www.vintagebrake.com/mastercylinder.htm

Michael (Mercury) Morse pulled together a nice little chart that tells you where you are. It doesn't include every variable but it's a great place to start.

teazer said:

http://www.vintagebrake.com/mastercylinder.htm

Click to expand...

I see this chart a lot, however the front brake on a CB350G/CB360/CB450, etc... is a single 38mm piston with a 14mm master. This would yield a ratio of 7.37:1 according to the chart, but in the writeup it says 'single piston calipers are much happier in the 14:1 to 12:1 range'. The suggestion that the stock brake setup is way outside what's acceptable has made me take this chart with a grain of salt...

jonwright said:

well i am just gonna get the same one you got thats 12.7, since i know yours works, its really gonna be the cheapest option for me. did you use the brake light switch on the lever or did you run it through the same stock cb360 tree mount switch? i have clipons so i am probably going to get the braided line set. anything else special you had to do to get this MC on your cb360?

Click to expand...

Just bolted it on... easy! I got s/s lines as well. I'm gonna use the switch that came on it.

rock on, thats great info, thanks a lot buddy. im looking forward to getting it. was your caliper piston siezed when you did your brakes? what was the easiest way to get it all working?

Overdraft, Good point but he's right on with RD350 and teh way they work nicely with smaller M/C. We tried 11mm, 12mm, 1/2", 13mm, 14mm, 5/8" and ended up with 12mm as the best balance between power and feeling. It's still a poor brake but it's much better than stock.

Fitted an 11mm to another RD and that barley applied the brakes. Point of the story, is that the chart is a good place to start. We also know that none of the manufacturers made very good brakes back in the day so it's worth experimenting a little.