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jon0881

Beta evo front brake

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Hi,

I was hoping someone can help me with what i need to fix here. The front brake on my beta evo is playing up. They work fine but there is a load of empty slack on the first part of the lever. The adjusters are all the way in. Its like there is a load of empty slack not in the lever as the piston moves in. I pulled off the front wheel and im pretty sure the pads are good. A while back i stripped and cleaned down and it was better but its back to crap again

 

/Jon

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you may find it easier ( and in my experience, a better result) if you bleed in the normal way to get the majority of the air from the system, adjust the levers to give the correct free play and travel, then tie the lever back to the bars with the reservoir cap removed or at least loose and leave for a few days... the system will (or should) self bleed....from time to time, I also leave the front and rear brakes tied in between rides, just to keep them pumped up.   

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Brake fluid is very hygroscopic, so it will absorb moisture from the air. Moisture may affect brake feel and will corrode parts inside. This is why you're supposed to only use brake fluid  from sealed containers. I wouldn't leave master cylinder open.

Investment in "Hand Held Vacuum Brake Pump" is not a big expense (15pounds ebay). It will make job easy and will leave perfectly bled brakes. I am using one like that and bleeding is 5 min. job and done.

 

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If there is load of free play with the adjuster right in, it may be the the master cylinder piston is not fully returning out, so limiting the stroke of the piston.

Remove the brake lever and the rubber boot and you should see that the hollow end of the piston (with the small spring stuck in it) should stick out beyond the washer and circlip.  If not push in and out a few times and see if it returns fully. If not you need to strip and clean the master cylinder and maybe fit a seal kit. 

Main cause of the problem is a failed rubber boot allowing water/muck into the outer space round the piston end. If you also need a Jitsie or similar rubber boot kit make sure you get one for a Grimeca master cylinder, as others will not fit properly. 

Hope this helps!

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3 hours ago, overdale said:

If there is load of free play with the adjuster right in, it may be the the master cylinder piston is not fully returning out, so limiting the stroke of the piston.

Remove the brake lever and the rubber boot and you should see that the hollow end of the piston (with the small spring stuck in it) should stick out beyond the washer and circlip.  If not push in and out a few times and see if it returns fully. If not you need to strip and clean the master cylinder and maybe fit a seal kit. 

Main cause of the problem is a failed rubber boot allowing water/muck into the outer space round the piston end. If you also need a Jitsie or similar rubber boot kit make sure you get one for a Grimeca master cylinder, as others will not fit properly. 

Hope this helps!

Hi,

i took a look yesterday again. Pads and calliper are good. Levers are adjusted all the way in. I took it off and could see the spring but couldn’t see where the cup and pin is pushing against. I cleaned and lubed it but it’s still stuck inside. The boot is knackered so I think your right. Is it a service and seal kit I need then?

 

cheers

 

jon

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Yes best to buy a seal kit, it comes complete with plunger. You need an 11mm spanner to disconnect the hydraulic hose, fix the hose upright so air doesn't get in, then strip the master cylinder on the bench. 

Before removing the circlip,  clean any crud round that area, then After removing the circling and washer, if the plunger is stuck it can be pushed out with a small screwdriver from the oil outlet end.

Then just clean everything before assembly!

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5 hours ago, overdale said:

Yes best to buy a seal kit, it comes complete with plunger. You need an 11mm spanner to disconnect the hydraulic hose, fix the hose upright so air doesn't get in, then strip the master cylinder on the bench. 

Before removing the circlip,  clean any crud round that area, then After removing the circling and washer, if the plunger is stuck it can be pushed out with a small screwdriver from the oil outlet end.

Then just clean everything before assembly!

Well i need a seal kit anyway as the cone boot is knackered. From what i can see on the UK shops the seal kit is just the rubber boot and the rubber seal in the cap. Since ive got about a week or so, i might drain the fluid, remove the master cylinder and follow those steps before ordering anything. Hopefully i will see something trapped or worn

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10 hours ago, madmostin said:

Is the disk bent at all? 

Na its straight. When i pull the slack out the lever the brakes work just fine. Its like the piston is pushed in and wont return. The spring is still there so the lever comes back and with it all the slack.

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