Handle bar master cylinder sizing..

Does anyone out there know what would happen if I put the larger master cylinder on my front brake system?
I am supposed to have a 9/16" bore unit but I put on a 11/16" bore unit on, what ill affect, if any, should I expect??
Will the front brakes lock-up or just be grabby or what?

There is a formula for determining the m/c bore size in relation to the number of calipers, number and size of pistons in the caliper and fluid volume of the braking system....I don't know it but you could potentially have a high volume/low pressure condition which could cause poor braking(dangerous)...I leave that math to the people that designed the various braking systems and just put on the m/c bore size that the system calls for....in your case with a single disc a 9/16 m/c....Why you wanna change it anyway??

Yes...let us know how it turns out....do some tests with it before you head out into traffic... make sure you have full braking power under hard braking conditions and lever travel isn't increased too much.

I ask b/c I am converting my old 1970 Wide glide to new 1996 model hand controls. The old controls had a 3/4" bore and the new one has 11/16" bore. I just wanna make sure I don't kill myself thats all. I guess you could say I am doing some experimenting.
I put a 9/16" on the bike and the lever seems to travel its full distance and the brakes feel like they are not working properly. I think it's needs the 11/16" bore M/C. I'm put on the larger M/C and seems what happens. I will keep you guys posted as to what the results are. Thanks for your help guys!!

Replacing the 3/4" with the 11/16" should be good to go... you could also replace a 5/8" bore with 9/16".
I initially thought you had a single disc Evo and you wanted to replace the 9/16 with 11/16, which is why I didn't think it was a great idea

I'm thinking about doing the same conversion on a single disc '78 FLH
Is the WG single or dual disc?? I thought single disc shovels had a 5/8" and dual disc's had 3/4" bore which changed to 9/16 for single and 11/16 for dual on Evo's
keep us posted .....Good Luck

My WG is dual disk with a 3/4" bore. I am converting to a 11/16" bore 1996 year model controls. You can always find them in black on ebay. People change the black for chrome very often. I did the conversion on both my old shovels. You can have the black switch housings chromed for about $100 or just leave them black. The are 1000% better than the 1970's and 1980's style controls in looks and function.
I reccomend buying OEM HD handlebar control hardware ONLY and not the cheap chinese made imported junk.
The HD stuff is a lot better quality in terms of look, fit and finsh!
STOP BUYING CHINESE IMPORTS PEOPLE (if you can). We are slowing killing our country by buying from the chincs. Everyone wonders why there's no jobs available?? Our jobs are being sent overseas to the chinese bastages, that's why.
I know most of the HD parts are not made in the USA anyway but at least you will be supporting a US company in some way shape or form.
Thanks for listening, I'm done now.

Do you see what I mean now????
The slow decline of North America - Andres Oppenheimer - MiamiHerald.com