Tip of the day series- RD400 rear brake

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Tip of the day...
RD400 rear brake caliper and master cylinder tips.
When rebuilding the caliper, clean the seal grooves really good to remove rust build up under the seals which causes the pistons to not move freely.

ANYTIME when using compressed air to remove pistons always wrap in heavy towels... and point down or as Mark suggested to do it in a bucket to be safe!
Other tips from Mark here:  http://www.2strokeworld.net/forum/index.php?topic=1619.0

Most RD riders are not needing the wiper seals in the pistons like Yamaha used, Yamaha made them to ride off road and all servere road weather conditions, I would rather not use the wiper seals and just rebuild it every 5-6 years to make it work very well.
Just assemble with the single thick seal. Polish caliper pistons with fine semi chrome polish to clean well if not severely pitted.

Use the OEM Yamaha rebuild kit to use the special red grease that comes in the kit to pack in the groove before you put the seal in.
This will prevent rusting under the seal for long life of the caliper pistons sticking.

If using a stock rear RD400 master cylinder you must take out the brake fluid supply line fitting out of the master cylinder and make sure the tiny hole is clean. There is 2 under there going into the piston bore.
That tiny hole will cause the brake caliper not to retract all the way, then drag and build heat, then seize.







Layout of order of the piston internals.



Always use new pads and throw the anti-rattle shims in the trash and don't use them!
EBC for stock bikes and SBS pads are great, I prefer the SBS for a more aggressive pad set.
Check disk for runout anything over .015 in. is not good.

I should add this also...due to the OEM RD400 master cylinder rebuild kit no longer available from Yamaha (part # 1A1-20000-50-00)
When needing to rebuild the RD400 rear master cylinder, use a OEM Yamaha FJ 1100-1200 kit but re-use the stock RD shaft/piston and not the FJ shaft.
All your using is the rubber parts from this kit.
Yamaha Part # 2YK-W0042-50-00 about $50.

If not a track roadracing bike... use a Dot 5 silicone brake fluid and will stay corrosion free and not remove paint when getting on refinished parts.
This works well...



Fancier ones...

https://www.amazon.com/slp/dot-5-brake-fluid/mpx3dwz7eggh64b

For roadracer use Castrol racing dot 4 LMA



Chuck

[Hawaii-Mike]

Excellent info Chuck!

[RDFL]

Great write up. The grease is red rubber or o-ring grease is safe for rubber parts, won't swell or dissolve rubber.

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I'm going to do more of these "Tip of the Day" series to help you lost souls.... (sorry, due to lost info from the old site....)
Chuck

[Czakky]

 

[1976RD400C]

A small brass wire wheel in a Dremel tool works good to clean the seal grooves in the caliper.

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I have a 90* pick that I ground on the bench grinder to make a scraper with.
I also cheat as I have a bead blaster.... 8)
C