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PostPosted: Tue Mar 25, 2014 1:45 pm 
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Racing ECU (!!)
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Location: Parksville, BC, Canada
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Hi Folks!

About a year ago, shortly after I got the bike, I decided to flush the brake fluid front and rear. This was a really good idea as the fluid was old but was still clean so there was no debris or corrosion.

So I grabbed my trusty can of DOT3 that I buy in large quantities and flushed the brake fluid thoroughly. When you do this you should keep your bike near the garden hose so that you can rinse off the fluid that gets released as it will rot your bike if you leave it in place.

What did I find when I had nice clean fluid? Dramatically improved brake performance! The pedal and lever were solid and the brakes were very noticeably better in firmness and in grab.

Interesting thing happened though. During the heat of the summer at some point, about a month later, I noticed the lever/pedal were getting spongy again. It behaved very much as if air was in the system. So, I flushed the fluid again and sure enough, once more, the levers and brake action were dramatically improved.

Once more, about a month later, the brake performance dropped off again. As you can probably guess this was becoming a cycle. It took some time for me to figure out what was going on - the can of brake fluid I was using had some moisture in it. It was not a new container. It was clear and it was clean but it had been sitting around for a while.

So what was happening was that under hard breaking the fluid would boil and aerate the line.

To make a long story short, the second I bought a small and new container of DOT 4 brake fluid and flushed the lines once more, I managed to get what I was looking for, which is long lasting and excellent brake performance.

So here's the thing, I strongly recommend flushing your brake fluid every year with a small, new container of DOT4 fluid. It will not cost much at all but you will notice the improved brake performance. If i's been a few years since you flushed, you're going to notice a HUGE difference in brake performance.

Coming from the automotive trade, fresh fluid is less important. You don't tend to notice it as you do on a motorcycle. This is a great, nearly free, tip. It takes almost no time and pays big dividends. Go for it!

BTW, if you're considering buying stainless steel braided brake lines in an effort to improve your brake performance, do yourself a favor and try this first. I'm pretty sure you'll be very pleasantly surprised.

Anytime I consider buying stainless brake lines I always come to the fact that with properly flushed and fresh DOT 4 the brakes on this bike really are exceptional.

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Marvin Miller
cbr125world Store

...because every day is MotoGP day when you own a CBR 125r...


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PostPosted: Tue Mar 25, 2014 5:34 pm 
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Clutch Springs

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Location: Caledonia, Ontario, Canada
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Thanks for posting, good discussion.

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PostPosted: Tue Mar 25, 2014 5:34 pm 
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Performance Pack

Joined: Tue Mar 25, 2014 3:21 pm
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Do not use Dot 5 brake fluid without first changing ALL lines, pistons and seals to materials suited to it - AFAIK Dot 5 is silicone-based and will therefore eat up the seals intended for use with mineral oil-based fluids.

Brake fluid is hygroscopic - it readily absorbs moisture from the atmosphere; the oil doesn't mix with the (oil-based) fluid, but it does boil at a much lower temperature (100 deg C); Dot 4 boils at (from memory) about 130 and Dot 5 boils at about 160.
The brake fluid absorbs a lot of the heat generated during braking - and when those droplets of water vapourise is when you lose braking pressure - remember from High School physics that a liquid connot be compressed but vapour (in this case, steam) can be.

Stainless lines: I habitually replace all the hydralic lines on bikes we intend keeping with braided/stainless - and will soon do so for the CBR125.
Assuming that only the lines were changed on the crashed grey-import and no changes were made to master-cylinder or caliper sizes, the whole and sole cause of the crash was operator error: the brake lines are only pipes and cannot alter the ratio between pressure applied at the brake lever and subsequently transmitted to the caliper/pads.

Years ago, I replaced the OEM rubber brake lines on my wife's Moto Guzzi 850 Le Mans - and found that I was doing wheelies a LOT; fuel consumption also improved - as did braking immediacy.
What I found was that when the brakes were applied, the original rubber lines (which had apparently delaminated inside) were absorbing pressure (instead of transmitting it), swelling up - and gradually resuming their normal shape over several minutes - thereby effectively still applying pressure to the calipers all the while.
Changing the lines gave infinitely more positive brakes - when I wanted them! - hence the sudden "extra" power and improved fuel-burn.

FWIW, fitting stainless lines is pretty-much the first 'modification' made to CBR125 and 150 race-bikes here.


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PostPosted: Tue Mar 25, 2014 5:36 pm 
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Racing ECU (!!)
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Location: Parksville, BC, Canada
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Precis wrote:
Do not use Dot 5 brake fluid without first changing ALL lines, pistons and seals to materials suited to it - AFAIK Dot 5 is silicone-based and will therefore eat up the seals intended for use with mineral oil-based fluids.


Exactly. When I looked into the DOT 5 issue more closely I came to the conclusion that it's just not worth it.

Precis wrote:
Brake fluid is hygroscopic - it readily absorbs moisture from the atmosphere; the oil doesn't mix with the (oil-based) fluid, but it does boil at a much lower temperature (100 deg C); Dot 4 boils at (from memory) about 130 and Dot  5 boils at about 160.
The brake fluid absorbs a lot of the heat generated during braking - and when those droplets of water vapourise is when you lose braking pressure - remember from High School physics that a liquid connot be compressed but vapour (in this case, steam) can be.


Exactly. This describes what happened to me when I was installing 'new' DOT3 that had actually been around for a while and absorbed some moisture. The brakes were great until I really nailed them repeatedly and then, clearly, the moisture boiled and brake performance went downhill. I used to do some exotic MVAC work (automotive air conditioning) and it's nice to see someone who understands hygroscopic :top:

Precis wrote:
Stainless lines: I habitually replace all the hydralic lines on bikes we intend keeping with braided/stainless - and will soon do so for the CBR125.
Assuming that only the lines were changed on the crashed grey-import and no changes were made to master-cylinder or caliper sizes, the whole and sole cause of the crash was operator error: the brake lines are only pipes and cannot alter the ratio between pressure applied at the brake lever and subsequently transmitted to the caliper/pads.


I'd have to try this to be sure. One thing that comes to mind though, wouldn't the difference in break performance be increased pressure at the piston, made more rapidly, due to the fact that the rubber lines are not swelling and eating some of that loss? I would expect that breaking with steel lines would be sharper and faster as compared to rubber lines.

Precis wrote:
What I found was that when the brakes were applied, the original rubber lines (which had apparently delaminated inside) were absorbing pressure (instead of transmitting it), swelling up - and gradually resuming their normal shape over several minutes - thereby effectively still applying pressure to the calipers all the while.


This is something that comes up in the automotive industry a fair bit. The liner inside the hose tears in one spot and creates a 'flap'. When the brake fluid is pushed down past the 'flap' it's not an issue. When the pressure is released and the fluid tries to rise back up past the tear it opens and creates the 'flap'. At that point it becomes an obstruction and pressure is held at the caliper creating brake drag - as you mentioned.


Precis wrote:
FWIW, fitting stainless lines is pretty-much the first 'modification' made to CBR125 and 150 race-bikes here.


It's worth a lot! On the track I would certainly go stainless. But I'd have to try it up here to get real-world experience with it to see if your experience proves out. I'm still thinking that because there is no swelling of the rubber lines the brakes would apply faster and harder because there is much less pressure loss due to swelling.

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cbr125world Store

...because every day is MotoGP day when you own a CBR 125r...


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PostPosted: Thu Apr 24, 2014 10:20 pm 
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Clutch Springs
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Over the winter, as part of a larger maintenance and modification list that I did to my bike, I also flushed the brakes (front and rear) with DOT 4 Brake Fluid.

A couple of days ago, after having done all the winter work on her, I brought my bike out and put about an hour "in the seat" for the first time this season and the braking on my bike was WAY better! Overall clamping by the brakes as well as responsiveness was WAY improved over what I was having for braking last year!

The old brake fluid was very dirty ...to say the least!! It wasn't a nice clear colour, or even lightly tinted... It had the look of tea (colour wise).

My next general maintenance on the brake system will be to replace both the front and rear brake lines. I've used HEL brake lines in the past and have found them to be of VERY good quality. One of the nicer things about their products is that you can order the out sleeve in different colours as well as the Banjo's.

On my SR50 I have a set of HEL lines with a translucent red outer covering (this allows the Stainless Steel braid to show) and in the Banjo's are also in Stainless Steel. I had thought about getting them in Titanium, but decided on S.S.

Cheers!!


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PostPosted: Thu Apr 24, 2014 10:44 pm 
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Racing ECU (!!)
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Location: Parksville, BC, Canada
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grenadiers wrote:
A couple of days ago, after having done all the winter work on her, I brought my bike out and put about an hour "in the seat" for the first time this season and the braking on my bike was WAY better! Overall clamping by the brakes as well as responsiveness was WAY improved over what I was having for braking last year!


Yup, it's a big improvement and it's nearly free and, let's face it, it's important maintenance that must be done.

I ordered up a set of stainless lines the other day (one will probably arrive tomorrow) as I wanted to test out some of what precis was saying. I know they are pretty much a requirement for racing but in short order I'll find out if they are suitable for street use on our bikes (with new riders in mind). I also contacted HEL about distributing them because I felt they would make a nice addition to the site but unfortunately we couldn't come to terms on pricing etc.

But, right now my desk is covered again and that also means the bike is off-road for a short period :ohmy: Nice to hear that you got out for a much-needed ride though :top:

You won't believe what I've learned from pulling the engine apart. Turns out, it was a very good thing to do....in fact, if I had left it any longer things would not be good for me. As it turned out, I needed to pull the flywheel and you're supposed to have a proper flywheel puller. Believe it or not, I had a generic puller in my toolbox that worked :cool: I needed another set of hands though so I took the engine up to my buddy's shop and got him to do the pullin' while I held the puller on the flywheel. As part of that his mechanic came over and couldn't believe how small the engine is. I mentioned to him that it wasn't just the engine - that's also a 6-speed transmission! They were pretty shocked.

To that end, as you can see in the pics, my remote control for my Media Center is larger then the transmission... :laugh:


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Marvin Miller
cbr125world Store

...because every day is MotoGP day when you own a CBR 125r...
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PostPosted: Thu Apr 24, 2014 10:45 pm 
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So....there goes my desk again.... :blink:

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cbr125world Store

...because every day is MotoGP day when you own a CBR 125r...


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PostPosted: Thu Apr 24, 2014 11:53 pm 
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Clutch Springs
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Just a thought... Since you have the case apart, have you ever thought about painting it?

My SR50 engine is Aluminum and when I did the PFI conversion to it, I did the case in a flat black wrinkle finish. Looks REAL cool!!!


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PostPosted: Thu Apr 24, 2014 11:54 pm 
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Clutch Springs
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mmiller wrote:
So....there goes my desk again.... :blink:


LOL!! That's the way it goes sometimes...

After getting my bike out of my office, I now have some space!!


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PostPosted: Thu May 08, 2014 11:53 am 
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Racing ECU (!!)
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Location: Parksville, BC, Canada
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grenadiers wrote:
Over the winter, as part of a larger maintenance and modification list that I did to my bike, I also flushed the brakes (front and rear) with DOT 4 Brake Fluid.

A couple of days ago, after having done all the winter work on her, I brought my bike out and put about an hour "in the seat" for the first time this season and the braking on my bike was WAY better! Overall clamping by the brakes as well as responsiveness was WAY improved over what I was having for braking last year!

The old brake fluid was very dirty ...to say the least!! It wasn't a nice clear colour, or even lightly tinted... It had the look of tea (colour wise).

My next general maintenance on the brake system will be to replace both the front and rear brake lines. I've used HEL brake lines in the past and have found them to be of VERY good quality. One of the nicer things about their products is that you can order the out sleeve in different colours as well as the Banjo's.

On my SR50 I have a set of HEL lines with a translucent red outer covering (this allows the Stainless Steel braid to show) and in the Banjo's are also in Stainless Steel. I had thought about getting them in Titanium, but decided on S.S.

Cheers!!


Yeah, I can't wait to test them out. I installed them the other day and just went back and changed the front line around a bit for better routing. It's pretty easy to do (now) given the bike is all apart. Hopefully it's going to be something like this.... :cool:


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Marvin Miller
cbr125world Store

...because every day is MotoGP day when you own a CBR 125r...
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