Brake advice

Just looking for a bit of advice. I bought a SV650S Y model a couple of months ago. Not long after I got it the front brake seized. I stripped the calipers and replaced the piston seals etc and gave it all a good clean.

After putting everything back together and bleeding the system the brakes felt rotten. I had a mechanic look at it and he bled it again and it was a bit better. He suggested replacing the master cylinder to correct the problem.

I replaced this but it's still not much better. I'm getting him to have another look at it soon to see if he can get them feeling any better. I was thinking that it could posibly be the hoses.

Does anyone have any suggestions? Is replacing the hoses with braided ones worthwhile, I can get them done for circa £40. I know the brakes on the SV aren't going to be the best but they really do feel pretty bad at the moment.

Sorry for the long story.

[dirtydog]

If it's got the original brake hoses then i would change them as they're meant to be changed evry 5yrs.
Did you get anything on the pads?

I replaced the pads when I stripped the calipers so don't think it's anything to do with them. I don't think fluid is leaking out anywhere, the level hasn't moved anyway. I don't know if it is the original hoses or not. If I do replace them though, is it worth the extra for the braided hoses?

Braided hoses do sharpen the brakes up some on an older bike. My usual trick is to zip tie the brake lever back to the grip overnight, not too hard. This can get the last of the air bubbles out, or pop a weak seal so you know where the problem is.

Strip and rebuild the calipers, check you have not nipped a seal when rebuilding the calipers the first time. If you have they will be drawing air.

Also bleeding the brakes can be a bit awkward, the bubbles want to rise back up to the master cylender, some kind of pressure bleeding system may help. I made up on with an old bicyle inner tube cut open and one end tied off, you can put one end over the master cylender ( secured with a tiewrap) and pressurise the system with a few pumps of a pump then open the bleed nipples to allow the fluid to flow.

Thanks for the advice. I think I'll go for the braided hoses anyway and I'll let the mechanic look at it as I'm giving it to him for the MOT next week. I he can't bleed it any better then it looks like the rebuild may be reqired again.

Thanks again for the help.

[jambo]

Originally Posted by gavinsky23

After putting everything back together and bleeding the system the brakes felt rotten.

It's a little tricky to give good advice without you being a bit more specific about this.

If the dust and fluid seals are new, and were installed properly with red rubber grease, and the pistons were cleaned up properly, so that they would slide in by hand pressure only then you should be OK on the pistons themselves. A few things people often miss though:

The SV calipers are sliding ones and need to be able to move smoothly on the 2 long pins covered by the rubber boots. Were the caliper pins and recesses cleaned up, and re-greased? If not then they won't provide a smooth and even pressure to the braking surface.

Have you removed, cleaned and lubricated the brake lever? It's a 10 minute job but you'd be amazed at the difference in feel if there's old caked on dirt there. Some horrible feeling brakes have felt silky sooth after this has been done, others have thrown money at every other component before checking this.

Braided lines are not a miracle cure for duff brakes, but if all the mechanics are good and the action feels smooth, but with too much lever travel after being bled properly, it may be worth looking at new hoses. OE rubber hoses will probably cost more than braided steel items from Goodridge or HEL, so the smart thing is to buy braided if you're going to replace. That said I'm running the standard rubber hoses on my zx6r, 7 years on the brakes still feel good. I've got some braided lines to go on there, but have not bothered so far....

Jambo

[yorkie_chris]

Originally Posted by jambo

The SV calipers are sliding ones and need to be able to move smoothly on the 2 long pins covered by the rubber boots.

Sometimes the pin which is enturely encased in a rubber boot jams, the bore for the pin +boot to slide through corrodes, which squeezes it preventing proper movement.

[dirtydog]

Originally Posted by yorkie_chris

Sometimes the pin which is enturely encased in a rubber boot jams, the bore for the pin +boot to slide through corrodes, which squeezes it preventing proper movement.

Yeah i've had that problem on several SV calipers, the last one i did i had to use a hammer and punch to get the bracket off!

[yorkie_chris]

Easy enough to solve, just clean the bore and put it back with a bit of grease, I use rubber grease to be on the safe side.