re-re-building front master cyl 1980 GS550L

[gfk328]

I was hoping someone would have experience or point me to an exploded view of the front Master Cyl inner workings. My dad tried rebuilding the front MC with a kit but I think he may have put it back together incorrectly since there is no lever tension or fluid flow when bleeding....

I purchased a different OEM piston and Cup set wich includes everything that lives in the bore, to give it a go myself, it includes something that I'm not sure of though, a thin metal disc that I wanted to check where it was in the order of things as I did not tear down the original system I want to make sure I am replacing everything in the correct order... I cant find a detailed breakout of the order of the innards anywhere however.

Anybody have a picture or exploded drawing I can use?

Has anyone used a different aftermarket replacement for their bike? this model has a two sided caliper. I'd love to just find a bolt on solution...

Thanks

[mike_of_bbg]

I JUST installed this one last night:

http://cgi.ebay.com/ebaymotors/F-BRAKE-MASTER-CYLINDER-EX250-EX500-KLR600-WR500-KLR650-_W0QQcmdZViewItemQQhashZitem20bb3b9b77QQitemZ140580199287QQptZMotorcyclesQ5fPartsQ5fAccessories#ht_13303wt_1158

(I got it on auction not BiN so it was cheaper)

Not even finished yet. Just went for my first test drive and it did pretty well. I need to get the brake light hooked up and the mirror on. Although it seems to work OK, I'm kind of wishing I'd bought my first choice, the 13mm available at cb750supply.com (08-0262). AFAIK there's no rebuild kit for the one I just bought.

Of course my 82 550L has a single front caliper - IIRC the 80 550L has dual front calipers so you're likely to want a 16mm master instead of a 14mm. You might check out a few of the options at Mike's XS:

http://www.mikesxs.net/products-71.html#products

I have the guts from my old MC still on the shelf. Camera just broke but I'll see if I can take a phone pic.

When you're trying to get the MC started it really helps to have a vacuum pump. Or get a long tube to suck on:

http://members.dslextreme.com/users/bikecliff/images/brakes_odds-n-ends.html#A04

[mike_of_bbg]

BTW, I believe the metal disc you're talking about goes between the return spring and cup, and the piston.

[mike_of_bbg]

Attaching pic of how I think they go. Try some forum searches on "prime master cylinder" or "bleed master cylinder". Getting it to start is a frequent source of frustration.

[gfk328]

Thanks a million! That was it... My Dad, for some reason, put the copper disc in the bottom of the bore in front of the outlet LOL therefore no fluid flow...

I placed it where you picture it and it works like a champ, my guess is it works like some kind of check valve.

Thanks for the quick response, now on to the next issue to work on ;-)