Rear Master cylinder problems

[charlesd89]

Ok, it's me again. Sorry I'm taking up space, but I have a serious problem with my rear master cylinder. I've figured out what the issue is, but I don't have a solid solution. The piston that I got in the kit is too long (about 1 1/4"), so it goes beyond the hole that the fluid passes into when it enters the cylinder. The hole is about 1" from the bottom of the cylinder. So my options are: get a shorter piston (can't find one), get a whole new cylinder body (can't find one), or drill a hole farther up the cylinder so that the fluid can be pumped into the brake line. Here are some pics to illustrate. I hope this makes sense. Thanks


The hole below the entry hole goes no where. Can I drill through it? That would allow the fluid to be pumped. (piston is upside down... noobie move. You get the idea though)


Again, piston is upside down.

[charlesd89]

I meant "cylinder body is upside down" not "piston." My bad...

[TOOLS1]

I would try to find the right kit, or get another master cylinder. What year, and model bike is it?
TOOLS

[Hoosier Daddy]

Sorry, but your statements about "cant find one" are hard to believe. The aftermarket for a CB750 is about the best sellection you'll find. What is the year and model? Being rear disk I bet it's a F, but please let us know for sure.
I do not recommend drilling another port or enlarging one in you m/c. The factory engineers knew their shit. You have the wrong piston. The tiny hole is the fluid return to releave pressure after the brake is released. Common to plug up with debris so you can clean it, but don't change it.

[charlesd89]

It's an 81 750f. The master cylinder kit I bought was for an 81 750f.

[charlesd89]

Here's a link to the kit I bought:

http://www.ebay.com/itm/81-82-HONDA-CB900F-NEW-K-L-REAR-BRAKE-MASTER-CYLINDER-REBUILD-KIT-32-1075-/370772811025?pt=Motorcycles_Parts_Accessories&fits=Model%3ACB&hash=item5653c81d11&vxp=mtr

[shinyribs]

That link says 900F vs 750F. I dont know if there is a difference or not,just something I noticed.

Do you still have your old piston? Maybe use the original piston with the new seals?

[Hoosier Daddy]

Sorry if I came off short before, I was typing on my phone and trying to keep it ... well... short. 
It is kinda interesting, according to the K&L catalog, the 32-1075 you bought fits both the 81-82 CB750F and the CB900F... but it does show an 80 using a differeent kit, 32-1458.
Do you still have your original pieces? Granted most of the time the pictures of parts on e-bay are generic and for referance only, but did the original look more like this one?



The factory microfisch shows it looking much different than what you bought (but similar to K&L's '80 version). It is showing as still available OEM and to me, that would be the best way to go...http://www.servicehondapsn.com/fiche_section_detail

See group #10 below...

MASTER CYLINDER SET
43520-461-771 - $42.26


 

[charlesd89]

Unfortunately I didn't keep the original piston... major mistake. Thanks, Hoosier Daddy. I put in the order for that kit. I appreciate the help! I'll keep you posted on the results.

[Piute]

   
                           I find K-L parts to be confusing for the seller,
                On E-Bay ask all the thoughts and Questions you have before buying ,
                             THEN you will get a return for Right part ,
                      I know we hate the wait and search at time but DO IT.

                       Even with 750 sellers such as Vin. CB750,Dime guy's,
                     all sell the K-L after market parts that fit multiple bikes.
                           
                                     Electronics gets even funner

[Hoosier Daddy]

Good luck to you, hope it all works out... I think that was the best route.

[charlesd89]

So I followed the link you sent me Hoosier Daddy and ordered the master cylinder set from Service Honda (http://www.servicehondapsn.com/fiche_section_detail) but it's the same set as the original one I bought. The piston is exactly the same as the one that I already have...
I'm wondering if this kit will work: http://www.ebay.com/itm/Honda-CBX-CB750F-CB900C-Master-Cylinder-Rebuild-Kit-/160997439043?pt=Motorcycles_Parts_Accessories&hash=item257c31f643&vxp=mtr
The details say it fits 79-80 750f super sport. Can it fit an 81?

[hondacb750f]

are you sure it is the original master cylinder?,


   The reason I am asking is I received the same kit and it fit just fine. It did not fix my problem thou. I am here searching the threads for a answer. Good luck and Honda speed with you.