identifying master part

[2t Fan]

trying to identify the part on the left. Removed from a ASCO 5/8 master mounted on a RD350. The part on the right is from the master repair kit for RD350, but it is not the same as the old one !

[2t Fan]

more pics

[1976RD400C]

Two different manufacturers and they are using different piston designs. OEM Yamaha rebuild kit is not going to work on a aftermarket master cylinder.

[motodreams]

2nd that comment.  RD350 rebuild kit is for the RD350 OEM brake system.

[m in sc]

whos that 'master kit' from?  fwiw the master rebuild kit for an rd is the same as an xs of the same era. you can clean that plunger and just replace the seals. or fit a new master. if that's the old one, it must be pretty crusty inside.

[2t Fan]

The master repair kit is from Niche Cycle and I believe it's for the OE master

[2t Fan]

This is the master cylinder on the bike. Is this an OE master or taken from another model ?

[m in sc]

looks like the right one to me, the master.

the rebuild kits.. your 1st pic left a few parts out. this is from the niche page, i rearranged the parts in the order they should go in.. it should work just fine. the back disc takes place of the rear seal. the plunger shaft is just a different configuration but works the same. I have used similar in the past.

[2t Fan]

thanks a lot , will do so

[2t Fan]

fixed as suggested, but fluid is not flowing , what else to look 

[m in sc]

clean the holes in the master cylinder body, especially the small one, fill master with fluid off bike from banjo fitting side, then reservoir, and bench bleed.  also, what condition are the lines in? ive seen them rusted solid inside with gunk before.

[2t Fan]

lines are clear, will the master work with the new parts ? OE old master kit parts looks different.

[m in sc]

it should. but, if i were you, id just get a new master cylinder start from scratch. 

[2t Fan]

Rebuild kit  what Niche Cycle sell is different from the 1A0-W0041-00-00 kit ? Will that be a reason ?