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Discussion Starter · #1 ·
There was an old post on this subject, but it tailed off without a conclusion. I've fitted a Harrison 4 pot in place of the banana and it's rock hard at the lever. My research tells me that in order to retain the OE MC and get a better "feel" I need to sleeve it down to 9/16. Only thing is - which seal kit to use?

I checked the W&W site and they do a 9/16 for 82 up, but it does not include a retainer clip, so I'm wondering if anyone has successfully sleeved down an MC and which kit was used?

Would appreciate any advice.

Cheers.
 

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My wild ass guess, that maybe would work. Use a stock 3/4 rebuild kit. delete and replace the cup with a 9/16 cup, the spring will also be a delete and replace with a smaller diameter. Sleeve should be .001 press and end with enough room for install of the 3/4 retainer and washer from the 3/4 kit. A tool sized to fit for pressing the sleeve will be needed. Bleed holes get drilled after sleeve install and after sleeve bore should get honed to clean up the bore. Machine the 3/4 piston down to minus .002 of your sleeve bore, and cut a rear oring groove and use a smaller oring. Look for the cup only at old time auto parts stores that has been in business for more then 45 years, those old guys used to sell them separate, back when people didn't throw things that worked away.
 

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Discussion Starter · #4 ·
Thanks for the replies. I have found a company in the Uk that specialise in re-sleeving. They use stainless press fit and drill the holes as standard.

I can get a piston made for a few quid, but I've noticed that the OE piston has either holes at the front or, a serrated edge. That flummoxed me until I discovered that their purpose is to increase the vacuum when disengaging the brake. This sucks back the fluid and releases the force on the caliper piston. Here's the OE 3/4. Note serrated edge.

Font Camera accessory Auto part Metal Circle


Later kits do not have this feature - wonder why?

Here's the 9/16 kit from W&W.

Automotive tire Rim Font Bicycle part Auto part


So, I can get the sleeving done and as Joe says, retain the circlip, or cut a new groove and source a new clip. But, what about the serrated edge? Is it necessary and why did Harley not use it for later kits?

Maybe I'm overthinking this!
 

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Slots replaced the older holes with reed style valve type piston. Your 9/16 kit is likely a smaller diameter at the cup end to allow the same pressure release of the other types.
 

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Discussion Starter · #6 ·
Man, I've been mulling that over and over. Thanks for the insight - makes sense. Probably cheaper to manufacture too. I'm going to get a 9/16 kit and use the spring and cup for starters. If the piston lines up with plunger and holes I'll use that, or get one made up/modified. I'll keep you posted.
 

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Made or modified is what you will have to do. Match factory length, and depth of the pocket for the rod.
Here is the early style piston with a reed valve in this kit.
 

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Discussion Starter · #8 ·
Thanks again Joe. Interesting how they designed that early kit. They also made a plastic version of the piston with holes at the front. I've done quite a bit of generic research and there's not many that use that system today. Maybe they were trying to get the banana caliper to behave, instead of mounting it properly in the first place. I'll have to dig out my Donny Peterson books to see if he has anything to say on the matter.
 

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The master kit I showed pre-dates the banana by 14 years only change was the removal of the residual pressure valve in 1973. I had assumed you where doing the rear master. Is that correct or are you doing the front. 9/16 fronts are easy to get.
 

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Harrison are expensive but the only nice looking bolt on. might be good time to look for later model controls and sell the originals to offset cost or go for Jap mc
 

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Discussion Starter · #13 ·
The master kit I showed pre-dates the banana by 14 years only change was the removal of the residual pressure valve in 1973. I had assumed you where doing the rear master. Is that correct or are you doing the front. 9/16 fronts are easy to get.
It's the front and the idea is to retain the OE style whilst improving the braking and feel. Yes, that's my bike in the picture. I am aware that the later 9/16 are available, but the style and switchgear look odd on the older bike IMHO. Although, if it starts to get too complicated and expensive I'll have to think about a compromise and use a later MC. Here's a shot of the bike. This was taken before fitting a pogo seat and the Harrison

Wheel Tire Fuel tank Automotive fuel system Motor vehicle
 
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