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Replacing piston set in caliper GS450L

  • Thread starter Thread starter Lil_Red
  • Start date Start date
L

Lil_Red

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I've looked at the pics of how to do this in my Clymer's and it seems like it's something I can do myself. Are there any little tricks that might make this easier or would I be better off having the shop do it?
 
Replacing caliper piston boots and seals is a fairly easy job. I used to be wary of brakes, but now after getting three bikes, it is a piece of cake. And it is an important job to do even if the brakes seem fine. Brake fluid tends to absorb water from the air over time and gets contaminated. This causes all kinds of gook in your calipers and lines. If you have an air compressor you can do the job. That is needed to pop the piston out of the bore. Once out, clean everything meticulously and coat all internal parts with clean brake fluid before assembly. Make sure the bleeder valve is open and clean. Putting the rubber boot seal back on the piston and seating in the groove in the bore can be tricky at times, but have patience. Then follow the book and bleed the brakes.(sometimes this is easier to do with 2 people).
 
One trick is using compressed air in the inlet fitting to pop the piston out. Clean every thing and inspect the piston for nicks and pits - replace if not perfectly smooth in the sealing area. Don't use anything other than clean brake fluid to lube the parts when assembling. Use DOT 3/4 brake fluid, not the silicone DOT 5 stuff since it has drawbacks (do a search if you want to learn more). Good luck.
 
relic-rider said:
Replacing caliper piston boots and seals is a fairly easy job. I used to be wary of brakes, but now after getting three bikes, it is a piece of cake. And it is an important job to do even if the brakes seem fine. Brake fluid tends to absorb water from the air over time and gets contaminated. This causes all kinds of gook in your calipers and lines. If you have an air compressor you can do the job. That is needed to pop the piston out of the bore. Once out, clean everything meticulously and coat all internal parts with clean brake fluid before assembly. Make sure the bleeder valve is open and clean. Putting the rubber boot seal back on the piston and seating in the groove in the bore can be tricky at times, but have patience. Then follow the book and bleed the brakes.(sometimes this is easier to do with 2 people).
Click to expand...

Thanks. Bleeding brakes is definitely a two person job for me since I can't squeeze the brake and reach the bleeder bolt at the same time :).
 
Nessism said:
One trick is using compressed air in the inlet fitting to pop the piston out. Clean every thing and inspect the piston for nicks and pits - replace if not perfectly smooth in the sealing area. Don't use anything other than clean brake fluid to lube the parts when assembling. Use DOT 3/4 brake fluid, not the silicone DOT 5 stuff since it has drawbacks (do a search if you want to learn more). Good luck.
Click to expand...

Thanks. I have DOT3 fluid. I'm off to do a search on DOT5.

I'm sure I'll be back with more questions when the parts arrive and I start taking things apart. I'm also replacing the brake hose with a stainless hose at the same time. I figure if I do it all at once then I only need to bleed the system once.
 
Don't forget to use new crush washers when you change the brake line. And bleeding the brakes is easy by yourself. Prop up your bleed bottle on a box, pump the master with the right hand and crack the bleeder fitting with the left. Repeat until no more air.

Good luck.
 
Nessism said:
Don't forget to use new crush washers when you change the brake line. And bleeding the brakes is easy by yourself. Prop up your bleed bottle on a box, pump the master with the right hand and crack the bleeder fitting with the left. Repeat until no more air.

Good luck.
Click to expand...

Thanks for the washer tip. I've tried that bleeding method in the past but I seem to lack some crucial bit of coordination plus it's more fun to drag my husband out of our AC'd house to help :).
 
I use one of those hand vacuum pumps to do the job myself. No need to pump the master cylinder. I think mine is Mity Vac brand. A real handy tool. Costs like $30.
 
relic-rider said:
I use one of those hand vacuum pumps to do the job myself. No need to pump the master cylinder. I think mine is Mity Vac brand. A real handy tool. Costs like $30.
Click to expand...

So you top off the fluid, close up the reservoir and then use the vacuum pump to suck the air out?
 
You don't have to close up the reservoir. Just keep it topped up. Put the hose from the pump on the bleeder, pump it up by hand, then crack the bleeder, and close it before the vacuum goes low. Do this until the fluid comes out without air. The pump comes with a little reservoir that the brake fluid goes into after being bled out.
This model 7000 is like what I have:

http://www.mityvac.com/pages/products_hvpk.asp#07000
 
relic-rider said:
You don't have to close up the reservoir. Just keep it topped up. Put the hose from the pump on the bleeder, pump it up by hand, then crack the bleeder, and close it before the vacuum goes low. Do this until the fluid comes out without air. The pump comes with a little reservoir that the brake fluid goes into after being bled out.
This model 7000 is like what I have:

http://www.mityvac.com/pages/products_hvpk.asp#07000
Click to expand...

Thanks! I'm going to check it out. Sounds like a handy little device :).
 
Lil_Red said:
Thanks. I have DOT3 fluid. I'm off to do a search on DOT5.
Click to expand...

Feel free to to some research on DOT5, but be aware that mere street bikes will not be able to make use of its advantages. And, the cost and effort of the changeover is not fun. Better to stick with DOT3 or DOT4, which has a higher boiling point.

To use a MityVac to bleed the brakes, it still helps to have two people, but the job is so much easier. As mentioned before, connect the vacuum hose to the bleed nipple, pump up a bit of vacuum, it does not have to be much. Open the bleed nipple, watch the fluid (and the bubbles) coming out of the caliper. The second person can keep the master cylinder topped off. As fluid is drawn through the system, the vacuum will decrease, so just give it a couple of pumps every so often to maintain fluid flow. When no more bubbles appear, close the bleed nipple. One more thing before it's ready to ride. Find some rope or wire. Squeeze the brake lever, tie it in place with the rope or wire, rotate the handlebars so the master cylinder is the highest point in the brake system and leave it overnight. Even with careful bleeding, there are invariably very small bubbles still in the system. This allows them to migrate up the hose and into the master cylinder where it does not matter.


.
 
Steve said:
Feel free to to some research on DOT5, but be aware that mere street bikes will not be able to make use of its advantages. And, the cost and effort of the changeover is not fun. Better to stick with DOT3 or DOT4, which has a higher boiling point.

To use a MityVac to bleed the brakes, it still helps to have two people, but the job is so much easier. As mentioned before, connect the vacuum hose to the bleed nipple, pump up a bit of vacuum, it does not have to be much. Open the bleed nipple, watch the fluid (and the bubbles) coming out of the caliper. The second person can keep the master cylinder topped off. As fluid is drawn through the system, the vacuum will decrease, so just give it a couple of pumps every so often to maintain fluid flow. When no more bubbles appear, close the bleed nipple. One more thing before it's ready to ride. Find some rope or wire. Squeeze the brake lever, tie it in place with the rope or wire, rotate the handlebars so the master cylinder is the highest point in the brake system and leave it overnight. Even with careful bleeding, there are invariably very small bubbles still in the system. This allows them to migrate up the hose and into the master cylinder where it does not matter.


.
Click to expand...

I've read about the DOT5 and I think I'm going to avoid it and stick with the tried and true :).

Thanks for the additional tips on bleeding. I'll do that. Now, if only the parts would get here so I can get started.
 
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