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22-06-18, 02:30 PM | #21 |
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Re: Bleedin' Brakes
yup lever 'rattling' helps getting stubborn systems started. what you do is flick the end of the lever about 10mm very fast (like a jack hammer), this dislodges the air in the MC.
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25-06-18, 07:13 AM | #22 |
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Re: Bleedin' Brakes
ok so the mystery deepens......
The good condition MC arrived, i fitted it and bleed the brakes every which way again....lever still not firm. Tried the fast flicking (missus got jealous ) but it didn't help. Had i just regretted buying a "good condition" MC cylinder and should i have just bitten the bullet and spent £150 on a new nissin MC? Now here is the odd thing, whilst i was here this time it thought i would install the new discs i had lying around. Well, as soon as i installed, a quick bleed again and the lever was a lot firmer now and less travel?! WTF? It still wasn't right though and as it was getting late i just clamped the lever back to the bar overnight. When i went to have a look in the morning once i released the lever it was still slightly firm (although still slightly better than before) but i now had a pool of brake fluid on the floor from the NS caliper. Took the caliper off and it seems the pressure overnight had forced it way past the new piston seal on one of the pots. So it look like i may have pinched the seal when i rebuilt the caliper, but not sure why it didn't do this before, i'm assuming because it wasn't building up any pressure in the system. So fingers crossed, if i remove the faulty piston, check the seals, re-grease and put it back together i am hoping this will resolve the issue. So it would appear the a mix between new discs and a leaky seal (which didn't show up until the discs went on) was the solution |
25-06-18, 08:17 AM | #23 |
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Re: Bleedin' Brakes
Glad you are getting somewhere.Always the same with older systems that have not been regularly serviced.Starts off as a 10 min job etc.....
Then something else goes once things are disturbed
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25-06-18, 08:39 AM | #24 |
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Re: Bleedin' Brakes
yes very much tested my sanity!
Piston bores were clean and unscored. I deliberately made sure all was good as i was putting in new OEM pistons and seals and given the price of these i didn't want to be pulling these apart so soon or risk marking them when doing so. still no idea why new discs seemed to have resolved the problem though |
25-06-18, 09:54 AM | #25 |
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Re: Bleedin' Brakes
Were the bobbins seized on the old discs?
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25-06-18, 10:08 AM | #26 |
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Re: Bleedin' Brakes
nope they all freely turned by hand
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25-06-18, 08:46 PM | #27 |
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Re: Bleedin' Brakes
Be aware that when you rebuild calipers (and do a really good job) the pistons almost move to easily. This means when you try to bleed the system they move back fractionally when you release the lever (the suction part), giving excessive travel on the lever just as you describe. Once there is enough pressure to push them properly onto the pads and discs they usually say put and the lever firms up. I usually get round this by pumping the lever back and forth really quickly once the system is full and bled, this seems to get the fluid past the master cylinder before the pads have a chance to retract.
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