RD with Ninja Master Cylinder

[SmokeAddicted]

I installed a EBay Special Ninja 250 front brake master, and it feels sloppy.  Maybe I'm comparing this to modern bikes and shouldn't.

I'm estimating a 1/2" of throw before the pads apply stopping pressure to the rotor.

I've have bled, reverse bled, wasted a bottle of brake fluid, zip tie overnight, bled again, and absolutely no change. It's consistently mediocre. I can pull the lever to the bar, and it becomes progressively hard, BUT I can pull it to the bar (easier than I think I should). 

Is this common with the EX/Ninja master swap?

I have the repop Economy Cycle caliper. Stock rotor. No leaks as far as I can tell over the last 3 days. I'm fairly sure there is no air.

Am I missing something?

[Simmons1]

When you say eBay special do you mean a used one or a cheap Chinesium one?

Off the top of my head. If you are sure bleeding isn't the problem, maybe you got a bad one, or maybe the one you bought doesn't have the right piston size.

I am using a $13 11mm piston Chinesium master cylinder on my TDR 250 with a gold dot caliper and the lever is hard as a brick.

[1976RD400C]

Sounds like you did everything you could. Does it have an oem rubber brake hose? That may cause it to have some mush. You shouldn't be able to pull it back all the way to the handlebar.

[Dvsrd]

I had big problems when trying to use some "anti squeal" shims that came with a set of new pads. Binned them, and all was good.
My setup is an alloy repop caliper from EC, one piece steel braided teflon hose, 13 mm Brembo master cylinder, coffin style reservoir. Works great!

[Dvsrd]

I also suspect that using the stock brake light switch may increase lever travel a bit, and also make bleeding more difficult by potentially trapping air bubbles.

[1976RD400C]

You could test the master cylinder plugging where the hose mounts on it with the bolt and a stack of extra copper washers. Then see if the lever gets rock hard with little travel. If so, the problem is downstream from the master, probably still air in there.

[SmokeAddicted]

You could test the master cylinder plugging where the hose mounts on it with the bolt and a stack of extra copper washers. Then see if the lever gets rock hard with little travel. If so, the problem is downstream from the master, probably still air in there.

That's actually a really good idea. I'll give that shot

[SmokeAddicted]

I also suspect that using the stock brake light switch may increase lever travel a bit, and also make bleeding more difficult by potentially trapping air bubbles.

That's also something I have considered. I'm not sure what is stock, but it is a new pressure sensor. There is a switch built into the new master myself. I'll have spent a small fortune on brake fluid by the time this is over 

[SmokeAddicted]

I had big problems when trying to use some "anti squeal" shims that came with a set of new pads. Binned them, and all was good.
My setup is an alloy repop caliper from EC, one piece steel braided teflon hose, 13 mm Brembo master cylinder, coffin style reservoir. Works great!

You didn't use the shims that are included with the repop caliper? Starting to wonder if I can shim my way out of this or try a different set of . I've bled and reverse bled for 2 hours now and absolutely no different.

Only other thought is the master cylinder piston is too small and chalk it up to Chinese junk

[m in sc]

depends on the volume displacement per pull. its that simple. ive used a load of master's off ebay, usualy the 14mm ones work well w a stock rd350 caliper. stock is 16mm .

on the 72 r5 i used a round one from 'marti' i think, off ebay.

IF the piston throw is long enough, a smaller diameter you can get away w 11, 12mm etc masters

[SmokeAddicted]

depends on the volume displacement per pull. its that simple. ive used a load of master's off ebay, usualy the 14mm ones work well w a stock rd350 caliper. stock is 16mm .

on the 72 r5 i used a round one from 'marti' i think, off ebay.

IF the piston throw is long enough, a smaller diameter you can get away w 11, 12mm etc masters

The Ninja piston size is 12.7mm. It builds pressure to a point, and pressure increases as the lever travels, but gets stopped by the throttle tube. Same result over the last 4 times I've drained the whole system. That's gotta be the issue. I can't fathom the same amount of air getting trapped for the grand total of 4 times over 2 days.

[m in sc]

yeah, you need a 14mm master

[SmokeAddicted]

M in SC, because you're the guru, and I've endlessly searched eBay, can you recommend a remote reservoir (or dirt bike style) master that will mate to a repop EC caliper with the stock banjo bolt sizes? I have a stock master, but real estate is the problem. One that might not kill me if I sneeze nearby.

I have the line and crush washers, etc.

At this point, I'm borderline desperate.  Trying to get the bike "finished" for Deals Gap, and it fights me every step of the way.

[m in sc]

this is the last one i bought fir use with an rd caliper. m10x1 25 thread, i use a pressure switch banjo bolt brake swith.

https://www.ebay.com/itm/203195849495

i bought this for the tzr,its perfect for that.it has a blue dot fz caliper i think its a 14 master.

https://www.ebay.com/itm/144916691931

[SmokeAddicted]

I'm glad you listed out the second master. That's the next project and makes things a bit easier. Appreciate your help!