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The 2-Stroke Garage => Turning Wrenches => Topic started by: ElFuegoBlanco on October 25, 2020, 02:37:27 PM

Title: Direct swap front master cylinder for 76 RD400?
Post by: ElFuegoBlanco on October 25, 2020, 02:37:27 PM
I rebuilt my front master cylinder a few months back. It took quite a long time to build up pressure in the brake and finally bleed them. All was (apparently) good. Fast forward to today when I pulled the front brake lever and had no pressure. The MC reservoir was bone dry. The bike has been on a lift since I rebuilt the MC and I don't see any evidence of a leak. I'm baffled.

At any rate, I'd feel more comfortable just replacing the MC. I was skeptical it could be rebuilt based on the condition it was in when I got it.

What is a decently priced replacement with a LH mirror? I've seen plenty of reproduction units, but they all have RH mirror threads. I normally wouldn't care, but I just bought mirrors. I'm not looking for anything 100% period. Just something that would bolt up and help me stop.

Thanks, Rob
Title: Re: Direct swap front master cylinder for 76 RD400?
Post by: Dvsrd on October 25, 2020, 03:09:03 PM
On my 350A, I have a 13 mm Brembo MC, with a rectangular integrated reservoir
It has RH thread, but a commonly available LH/RH adapter fixes that issue. And a matching RH/RH adapter for the other mirror keep things symmetrical.
A smaller MC also improves the brake feel and effort a lot. And the integrated micro switch.allows you to remove the stock unit and use a single line instead.
Title: Re: Direct swap front master cylinder for 76 RD400?
Post by: pidjones on October 25, 2020, 04:21:47 PM
Brake fluid doesn't evaporate in a couple months. You have a leak that you need to find and fix before changing out anything.
Title: Re: Direct swap front master cylinder for 76 RD400?
Post by: Organicjedi on October 25, 2020, 05:05:07 PM
A guru on the forum here (Chuck) has said that a new 14mm SR400 front master bolts right on and has a better feel than the 15mm stock setup.

The mirror and brake light switch are compatible as well.
Title: Re: Direct swap front master cylinder for 76 RD400?
Post by: ElFuegoBlanco on October 25, 2020, 05:56:39 PM
Quote from: pidjones on October 25, 2020, 04:21:47 PM
Brake fluid doesn't evaporate in a couple months. You have a leak that you need to find and fix before changing out anything.

Absolutely. The fluid certainly went somewhere and I need to figure out where.

Quote from: Organicjedi on October 25, 2020, 05:05:07 PM
A guru on the forum here (Chuck) has said that a new 14mm SR400 front master bolts right on and has a better feel than the 15mm stock setup.

The mirror and brake light switch are compatible as well.

Excellent. Thanks for the advice.
Title: Re: Direct swap front master cylinder for 76 RD400?
Post by: Seizer on October 27, 2020, 09:42:09 AM
MikesXS "Slimline" 14mm works well and affordable.
Title: Re: Direct swap front master cylinder for 76 RD400?
Post by: paul1478 on October 27, 2020, 12:33:38 PM
Quote from: Organicjedi on October 25, 2020, 05:05:07 PM
A guru on the forum here (Chuck) has said that a new 14mm SR400 front master bolts right on and has a better feel than the 15mm stock setup.

The mirror and brake light switch are compatible as well.
this is what I have on my 400. looks and works perfect.