Author Topic: Master cylinder rebuild kit plunger seal too large  (Read 683 times)

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Offline HammerSchlagen

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Master cylinder rebuild kit plunger seal too large
« on: August 13, 2020, 05:11:04 PM »
I got a cb550 MC rebuild kit from Niche Cycles(ebay). So I broke down the old one, did a throrough clean and installed the new parts. First time doing this so I was a little confused that the after installation the piston would not return after being pressed. So I reinstalled the old piston with the new hardware and it slides perfectly. The rubber seal that goes over the piston is larger than the stock one. I've tried greasing it but no luck. I'm not sure how one could shave down a rubber boot like that, so I think Ill just install the old piston

Has anyone else experienced this with the rebuild kits?

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Offline 69cb750

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Re: Master cylinder rebuild kit plunger seal too large
« Reply #1 on: August 13, 2020, 05:36:19 PM »
I have replaced internal parts for three cb750 this year.
Order - Spring seat, spring, loose seal,plunger with 2nd seal, ...
The spring tries to push the parts out the bore until internal c clip installed.

Offline HammerSchlagen

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Re: Master cylinder rebuild kit plunger seal too large
« Reply #2 on: August 13, 2020, 05:51:43 PM »
I have replaced internal parts for three cb750 this year.
Order - Spring seat, spring, loose seal,plunger with 2nd seal, ...
The spring tries to push the parts out the bore until internal c clip installed.
sounds like you've never experienced this?. I know the order, I'm saying on the niche cycle rebuild kit, the rubber seal around the plunger is too wide.

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« Last Edit: August 13, 2020, 06:03:58 PM by HammerSchlagen »

Offline HammerSchlagen

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Re: Master cylinder rebuild kit plunger seal too large
« Reply #3 on: August 13, 2020, 06:06:40 PM »
I ordered a cheaper kit, lesson learned. Will be ordering a genuine Honda rebuild kit off 4into1

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Offline Johnie

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Re: Master cylinder rebuild kit plunger seal too large
« Reply #4 on: August 13, 2020, 06:47:37 PM »
OEM - superior to the aftermarket stuff. Correct...live and learn as many here have. Good luck with it.
1970 CB750K0 - Candy Ruby Red
1973 CB750K3 - Candy Bacchus Olive or Sunflake Orange
1970 Chevy Chevelle SS396 - Cortez Silver
1976 GL1000 Sulphur Yellow

Oshkosh, WI  USA

Offline Maraakate

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Re: Master cylinder rebuild kit plunger seal too large
« Reply #5 on: August 13, 2020, 08:18:07 PM »
OEM - superior to the aftermarket stuff. Correct...live and learn as many here have. Good luck with it.

Long time ago my old man was helping me fix my car, way before I ever knew anything about mechanics.  We had to fix a power steering leak and got new hoses from the autozone, went to compare the sizes when we got back and of course the aftermarket was just a touch too short to be useful.  He said: "That's what I hate about aftermarket.  It's always close, but no #$%*ing cigar!".  (As he threw the hose across the room).  I'll never forget it.  I try to use OEM whenever I can.
1977 CB550K
1979 CM400A