Pressurising brake fluid

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Pressurising brake fluid

Postby Janovich » Sat Feb 15, 2020 8:03 am

Hey

Reinstalled the front brakes with a new brake caliper.
I don't have a brake fluid vacuum, what is the best practice to pressurize the frontal brake system without one?
Right now when I pull the brake lever it brakes but way too weakly
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Re: Pressurising brake fluid

Postby ExTex77 » Sat Feb 15, 2020 10:29 am

You can bleed the brakes without a vacuum.
(and with less hassle). Easiest with 2 people

get the appropriate soft hose to fit over the bleed nipple on the caliper.
get a container for the waste fluid.
I use a peanut butter jar with a lid & drill a close-fit hole in the lid for the soft tubing entry.
Also a smaller vent hole)

Open the master cylinder (MC) cover and remove diaphragm.
Use a turkey baster or syringe (from Wal Mart) to remove most of the old fluid
Fill MC with clean, fresh, new fluid. Dot 3 or 4 as specified on the MC cover.

Use the brake lever to apply pressure to the MC (pump the lever if necessary)
After/while applying pressure to the MC, crack open the bleeder nipple (use small wrench to turn nipple)
and allow fluid to drain into jar.
BE SURE to CLOSE the vent valve before the pressure is totally gone from the MC.

Repeat until fluid is low in the MC.
Add fresh fluid to the MC.

Repeat process until clean fluid is exiting the caliper.
Then adjust the fluid level in the MC and recover the MC.

All of the actions are done slowly to insure that the fluid does not splash on any painted surfaces.
Check the brake lever for firmness.

You probably can find a You-Tube video on the procedure.
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1989 Honda VTR250 & 1988 Honda NT650
Wife rides a Burgman 200 scooter and I enjoy riding it also
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Re: Pressurising brake fluid

Postby squirrelman jerry » Sat Feb 15, 2020 7:10 pm

lettus no if the above works4 u.
At 20 years old i wanted to be an architect; at 50, i wanted to be Harvey Weinstein's penis.
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Re: Pressurising brake fluid

Postby Janovich » Sun Feb 16, 2020 3:02 am

Thank you. It worked.
I'm glad my dad came in and told me the bleeder nipple itself should be rotated. I never looked at it like a moving part so it didn't occur to me I was doing it wrong.
When I opened and closed the bleeder nipple with a wrench while pumping the brake everything was fixed really quickly.
Thanks
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Re: Pressurising brake fluid

Postby Barbie & Skipper » Tue Feb 18, 2020 2:02 pm

One other trick that I've used for years: After bleeding the brakes, with the bike back on the sidestand, and the bars turned to the left, so the master cylinder is at its highest elevation, I strap *rubber bands/velcro straps/whatever) the brake lever tight to the handlebar to keep the system pressurized for a time. At least overnight, but sometimes several nights in a row. The extra pressure in the system seems to force any remaining micro-airbubbles up through the lines and into the master cylinder. It probably makes only a very small difference, but it does seem to take the last bit of squishyness out of the system.
Barbie - 89 VTR250 - 7k+, back on the road after 3 1/2 year vacation
Skipper - 90 VTR250 - 39k+, black & white, back on the road 22 years after first parked
Parts bike - 90 VTR250 - 20k+, "maintained" by idiots
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Re: Pressurising brake fluid

Postby Janovich » Sun Feb 23, 2020 9:09 am

Alright. Pressurizing the brakes wasn't so hard once I figured out the bleeding nipple thing, but I've been tackling another problem too which I already fixed but thought worthwhile sharing.

As we know, the brake disk of the VTR is unlike most brakedisks.
It is locked to the wheel at three points, making it prone to wiggle and misalign when installing. When you bolt down the circular rim cap it tightens the brake in place and aligns it flat with the wheel.
What was happening was that I pressurized the brakes before I bolted down the three rim cap screws. The pressure from the brake calipher had offset the brake disk slightly on the wheel, which meant that when the wheel rotated, it would run extremely 'tight' on the brake disk, hardly being able to move the wheel at all as the brake disk wiggled between the brake pads.
I fixed this by bolting down the protective ring first, so that the brake disk was completely locked in place and not being able to offset by the pressure of the brake caliper. Now the wheel runs freely again.

Hope that was comprehensible.
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Re: Pressurising brake fluid

Postby ExTex77 » Sun Feb 23, 2020 9:43 am

Thanks for this technique.

The "enclosed" brakes on the early VTR250s are different but I find that mine works well enough for my riding style.
I did install a braided hose for it, and that helped.

Ride safely
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1989 Honda VTR250 & 1988 Honda NT650
Wife rides a Burgman 200 scooter and I enjoy riding it also
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Re: Pressurising brake fluid

Postby Janovich » Sun Feb 23, 2020 10:02 am

Yeh the braking system itself is actually very decent. There are some advantages to the vtr250 brake disk as it won't overheat, won't bend, can be revised by sanding and likely never ever requires replacement; It's an unbreakable solid piece of metal (with heat vents) like those seen in cars.
The downside is that for most maintenance you have to take the front wheel off completely. Not very hard in itself but the VTR250 doesn't come with a rearstand meaning you have to find some other way to lift the frontwheel off the ground (I lift it up and put wooden blocks under the oil pan), which makes cleaning the brake disk is a hassle. Assembling everything back together is a bit of work but I've done so a dozen times in the last couple of weeks already as I replaced the front-tire and it can be done fairly quickly fortunately.

I enjoy the rear drum brakes too but I've had the rear wheel lock up several times (which makes the rear slide) on me already, its a very powerful brake for the weight of the bike which can be good but also dangerous as when braking the weight of the bike is transfered to the front wheel which allows the rear wheel to lock up.
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Re: Pressurising brake fluid

Postby Barbie & Skipper » Fri Feb 28, 2020 10:54 pm

Over the years, I've picked up some habits, good or bad, when riding w/o ABS.
On the VTR's, I seldom use the back brake, for 2 major reasons. 1) It's almost impossible to find a replacement rear wheel if you wear out the rear brake 2) I don't like locking up the rear.
I lower the rear brake (and shifter, for that matter) lever on most of my bikes to reduce the chance of lockup. It's more comfortable for me, almost all of the necessary stopping force comes from the front brakes anyway, and it's still easy enough to use the rear brake for corner entry and parking lot maneuvers when needed.

IMHO, it's far better to become comfortable with using the power of the front brake, and to use the rear brake sparingly.
Barbie - 89 VTR250 - 7k+, back on the road after 3 1/2 year vacation
Skipper - 90 VTR250 - 39k+, black & white, back on the road 22 years after first parked
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