Spongy front brake

[swarrans]

Before I ever ride my GT750A again I really need to sort out the front brake to avoid scaring myself too much!

The front brake is sort of OK but I have never been able to stop the spongy feel and the need to "pump it up" to get decent stopping power. I assumed it was/is air in the system but I've tried bleeding it in every way known to man and still can't get a firm lever feel. This might be down to my own incompetence, but if the master cylinder seals are a bit knackered can this also feel like air in the system?

If I need to buy new MC seals is it genuine Suzuki parts only (gulp!) or are some of the aftermarket parts any good?

Thanks in advance

Simon

[senicoli]

Before I ever ride my GT750A again I really need to sort out the front brake to avoid scaring myself too much!

The front brake is sort of OK but I have never been able to stop the spongy feel and the need to "pump it up" to get decent stopping power. I assumed it was/is air in the system but I've tried bleeding it in every way known to man and still can't get a firm lever feel. This might be down to my own incompetence, but if the master cylinder seals are a bit knackered can this also feel like air in the system?

If I need to buy new MC seals is it genuine Suzuki parts only (gulp!) or are some of the aftermarket parts any good?

Thanks in advance

Simon

I went for the aftermarket M/C seal kit what a waste of time and money half of did not fit the rest of it let more air in than when I started bite the bullet fit the correct parts this is brakes we are talking how much do you value your life colin

[RobMc]

I had a KZ1000 and I`d refurbished the brake reservoir and refilled the system,the brake seemed spongy and I was given a tip which did work.Get a cable tie,apply the front brake and tighten the cable tie on the brake lever/handle grip so the brake is being applied,leave it like this overnight and if there`s any air in the system it will find it`s way into the reservoir-the brake was great after that..This may not be the answer to your problem but those twin disc setups can be very difficult to bleed properly as I found out..

[PaulD738]

First of all bite the bullet and buy genuine Suzuki, as said above pattern seal kits can be variable in quality and fit. Clean everything SCRUPULOUSLY use fresh fluid and check the breather hole (the small one) in the bottom of the reservoir is clear. If your still having problems getting rid of all the air buy a big syringe from your local vets and try “reverse bleeding” from the brake nipple upwards. Another trick I found while racing TZ Yamaha’s was to remove the calipers and hold them above the master cylinder while bleeding them, put a piece of wood or similar between the brake pads while doing this. Good luck and let us know how you get on.

[swarrans]

Yep as I said in the intro I have tried "every way to bleed it known to man" including all the ones suggested and many others but still have the problem - but thanks for the comments anyway.

Back to the actual question - can a problem with the seals or anything related to the master cylinder cause the same spongy feel symptoms? The central reason for asking is I don't want to start replacing seals etc if there is no chance they could be the problem.

Having read Waterbuffalo's thread on changing the master cylinder and lever to a more modern set up I might even consider going that route if it could give a bit more braking performance over stock. (I have a cbx and it is a common mod replacing the master cylinder assembly for a more modern type with a different bore to get more brake pressure)

[PaulD738]

Do make sure the breather hole in the bottom of the reservoir is clear, it’s a very small hole and is easily blocked up and will give the exact symptoms you’ve described.

[mizzytheman]

Do make sure the breather hole in the bottom of the reservoir is clear, it’s a very small hole and is easily blocked up and will give the exact symptoms you’ve described.

If all else fails try putting viagra in the master cylinder. It doesn’t last very long and you’ll have to repeat the process evertime you go for a ride.

[senicoli]

the answer to your question is yes the reason its spongy is because there is air inside it process of elimination start at one end clean everything replace every seal I did this on the GT750L it is now firmer than than the front brake on my 16 plate GSX 1000 colin

[JNNNGS]

Simon,

It may be the brake hoses "flexing" under pressure. New hoses / stainless braided hoses may be the answer.

Paul.

[senicoli]

the answer to your question is yes the reason its spongy is because there is air inside it process of elimination start at one end clean everything replace every seal I did this on the GT750L it is now firmer than than the front brake on my 16 plate GSX 1000 colin

sorry forgot to mention fitted stainless hoses as well colin