front brake system

[aragami]

Hi guys,

After I put my new kit on my RVF and did all my repairs I kept losing pressure in my front brake system, causing me to have to bleed it every 2 days or so. I took the whole system apart tonight and checked everything out and all the lines and connections seemed fine. Put it back together and tried to bleed but I can't get any fluid to come down through the lines... Checked all the alignments of the banjo's and it's definately getting through the master cylinder.

There is defiantely some fluid getting through the lines, because I was getting some out of the clutch side lines, but I couldn't get any through the brake lever side... I know I'm probably missing something small here but for the life of me I can't think what it is!

And on a side note, has anyone fit a koso guage to an RVF? if so do you need custom mounts etc. and how hard is it to do?

Cheers guys.

[GregEason_NC30]

Hi aragami, it sounds like the master cylinder us passing, are you actually losing fluid or is it just pressure under braking. If it's just pressure, I would change the internals of the master cylinder. I think they're about £40-£60 for the kit from David silvers. Not a difficult job at all (famous last words...)

[amorti]

Hi aragami, it sounds like the master cylinder us passing, are you actually losing fluid or is it just pressure under braking. If it's just pressure, I would change the internals of the master cylinder. I think they're about £40-£60 for the kit from David silvers. Not a difficult job at all (famous last words...)

The rebuild kit is much less that that, though, ball-park is about £30.

Also worth replacing any copper washers which you have disturbed but not replaced. They will sometimes leak air in but not fluid, and you will never find the fault if that happens.

[aragami]

It's not losing fluid, just leaking in air... I think the more pressing issue is why can't I bleed the system!? haha, thanks guys.

[amaechizzle]

...Leak in air but not fluid. Sounds a little iffy to me.

Have ya tried gravity bleeding the system?

Pump the brake level 3 or 4 times, then on your 4th pump, hold it down.
Get a mate to work the brake lever, while you very quickly open and close the brake nipple.

Do this about 5 times, then try the lever.

[Cammo]

There is defiantely some fluid getting through the lines, because I was getting some out of the clutch side lines, but I couldn't get any through the brake lever side... I know I'm probably missing something small here but for the life of me I can't think what it is!

These master cylinders have a reputation for being a PITA to bleed sometimes.

Make sure you've removed all the air form the master cylinder - it's the highest part of the system and air can easily be trapped here stopping pressure from building. This is a common issue.

You can remove any air by pumping the level to create pressure, hold it in and crack the master cylinder bolt a fraction. You'll see fluid and bubbles come out if there was air in the m/c. Best to wrap a rag around the lines to mop up any fluid. Keep doing this until just fluid comes out (no bubbles). Then move on to bleeding the calipers.

For less mess buy one of these bolts that has a bleed nipple http://www.ebay.com.au/itm/HRC-DOUBLE-B ... 1277wt_905

When you've got it all bled to a decent pressure, tie the lever back to the handlebar (cable tie or rubber band) and leave it overnight. Bleed each caliper again in the morning. This will often help remove any residual air.

[amorti]

Still the most likely is from the first post. There are two seals in the master cylinder. If the first seal goes, you will get no pressure in the system, but you also won't get any leaks.

I assumed you would already have bled the top banjo bolt by now, if you haven't and if that doesn't solve it, you probably need a master cylinder rebuild kit. Now while you're there you might as well spend 50p on a full set of copper washers and replace them all. It probably isn't your issue, but it doesn't hurt to change them and they are very cheap.

[lizard821000]

as said already, its a pretty simple design and not much can go wrong, main culprit would be master, so rebuild that. the rest of the system are just lines and washers.

[aragami]

I've been at work all day so I haven't had a chance to give any of these ideas a crack... I'll give it a go tomorrow afternoon and report back with results.

[aragami]

Tried bleeding the master cylinder and that was a no go, still no pressure through the lines. I've ordered a re-build kit from DS' so hopefully that will solve my issues. While I'm at it, anyone know where I can get a new brake line kit? I may as well just replace the lines while i'm at it, to cover all my bases.