GT550 - The curse of a leaking brake bleed nipple

[PaulD738]

For once I'm in agreement with Paul on tbat one.

Who are you and what have you done with my mate Alan?

[Syd]

Well, finally sorted out the front caliper brake nipple sealing problem, however after bleeding the brake system over 8 times over the last month or so, the front brake lever is still spongy and not right. The entire front brake system is new and every time you bleed it with no fine bubbles in the oil and leave it over night with a zip tie on the level to help bleed out any tiny bubbles it still its not 100% right. Is there a trick to bleeding GT550 front brakes? Should the bike be on the side stand to ensure the actual oil level in the reservoir is at the highest point so no air can get trapped between the reservoir and the rest of the fittings? Are you best to use a vacuum brake bleeder at the caliper rather than the traditional method? Any helpful tips would be greatly appreciated.

[yeadon_m]

Syd,
I'll start by saying 'I don't know', so all that follows is speculative.
But observations from my various GTs over the years:
1 - even new brake lines flex a little. Do you have someone else's GT brake lever to compare your 550 to? if you're comparing it with a modern bike, it may be you're expecting a really solid lever. I'll assume it actually is soft, and that this isn't it! I will say that my GT750 and 550 have new Suzuki lines and there's a little squishiness but my GT380 has stainless lines and its as solid a feel as my modern.
2 - unless the brake disc and caliper and its pads are all 100.00% aligned, actual metal parts will flex when the lever is pulled. Inspect ultra closely and use finger tips on two components for feel for movement (when you pull the lever) as guides. If its something here, no amount of bleeding will help you! A favourite is non-parallel pads when new, especially if the fixed pad isn't totally flat against the caliper half. This will improve rapidly if you go out and do a series of steady stops from speed. Another is those wretched sliding pins one which the caliper is meant to move. Often, one will slide and the other binds, resulting is a minor change in the orientation of the caliper when the lever is pulled (you will be able to feel this even if you cannot see it).
3 - there is still some air in it (ducks).
Cheers,
Mike

[BATTS]

What DOT type of fluid are you using? DOT 5 silicon based fluids always give a spongier feel than glycol based fluids eg DOT 4 and 5.1.

[BAZ]

Feel is the same with all but .5 wont effect paint so use it !

[Syd]

Thanks for the info - I don't have another GT550 to compare my brake with, just my Kawasaki H1 & H2. My H1 front brake is really good, however when I fitted the second front disc option to my H2, I used a hose set from cruzinimage and its a bit soft as well. I also fitted a hose set from cruzinimage for the GT550 so maybe the hoses are part of the problem? I am using DOT 4 oil.

I'll check out the caliper movement as up unit now, the front wheel has been clamped on the bike lift and I have not rotated the front wheel at all when using the front brake which may help center the travel of the caliper and pads etc - maybe worth a crack?

[Alan H]

If you have twin discs and only a single disc type master cylinder, the brakes will be poor. Dual disc master cylinders have a larger diameter piston.Fit a Bandit 1200 master cylinder, or a GT750 m/s with a D underneath it (for 'dual') if you want it a bit more original. Braided hoses are better too. Sod originality when it's your life on the line.

[Syd]

Thanks Alan, I forget to mention that on the H2, I did replace the oil reservoir as well with a larger type to allow for the second disc - cheers