Bleeding Front Brakes on a GT750

pikeslayer · Post by **pikeslayer** » Fri Jan 22, 2010 1:11 pm

Well, there goes another $50. I'll get a rebuild kit ordered. Also need to get one one of those petcock screens. I'll let ya know what happens after the rebuild.

Post by **oldjapanesebikes** » Fri Jan 22, 2010 2:03 pm

tz375 wrote:Allan is right, and I'd just add that if you can't get a firm brake feel, then it is highly likely that the M/C is "bad".

Or 'soft' hoses .....

Post by **Suzsmokeyallan** » Fri Jan 22, 2010 2:19 pm

Look at it this way, at least you can still get the parts. Try doing that with some more modern bikes and it may surprise you,,,,sorry that part is NLA...

tz375 · Post by **tz375** » Fri Jan 22, 2010 2:57 pm

If the bike isn't on the road this week, pull the M/C and take time to strip and clean it and then you can decided whether it needs new rubber or if it's all scored and pitted.

I wouldn't spend the cash until I had it stripped and know what's up. But I'm that way.

pikeslayer · Post by **pikeslayer** » Fri Jan 22, 2010 3:30 pm

tz375 wrote:If the bike isn't on the road this week, pull the M/C and take time to strip and clean it and then you can decided whether it needs new rubber or if it's all scored and pitted.

I wouldn't spend the cash until I had it stripped and know what's up. But I'm that way.

I think I will do that. I'm that way too. Thanks TZ.

Post by **Suzsmokeyallan** » Fri Jan 22, 2010 5:44 pm

I know what you two are thinking and it makes sense to pull it down and verify the inner condition of the unit.
So suppose its not pitted in the bore, then you need a kit, and suppose it is pitted and you cant use it but you can locate a good second hand one, then you still need a kit to put in that one anyways.
Its the nature of the beast, what you dont have at that time, is what you will always need,,LOLOL

pikeslayer · Post by **pikeslayer** » Fri Jan 22, 2010 10:31 pm

So if it's not pitted, I need a kit? If I take it apart and its fine, I need a kit? Is something destroyed when I take it apart?

Post by **Suzsmokeyallan** » Sat Jan 23, 2010 5:59 am

The main issues that require a kit is the condition of the rubber seals. They are made with a 'sealing flare' so they can grip against the walls of the bore and only push the fluid forward. Over time this 'flare' gets weakened, worn and scored if the bore is compromised, causing the fluid to weep past or leak past them badly.
Basically, in a master cylinder such as on the GT,if the front one leaks you get no outflow pressure, if the back one leaks you get fluid on your hand, literally.
You rebuilt the calipers and no doubt saw the two square section circular rings that you put in by the boots that seal the fluid in the caliper.
Well they also have a 'sealing flare' design but its not in the ring itself its designed into the groove of the caliper body.
Looking down into the caliper,the portion of the groove at the back is shallower at the bottom than at the top so the ring sits skewed and creates the sealing flare.
If it wasnt designed so, the brake fluid would pass right around the seal, and naturally if the piston gets pitted or the ring wears, it leaks as well.
Also, its standard shop procedure that whenever you disassemble components such as in a brake system, you never reuse any of the main rubber components such as seals.

pikeslayer · Post by **pikeslayer** » Sat Jan 23, 2010 12:11 pm

It's apart. What a bit(h! Snap ring broke. Time to order a rebuild kit.

Post by **Suzsmokeyallan** » Sat Jan 23, 2010 6:10 pm

The snap rings are a pain, usually you can pull one eye inwards till the ring is small enough to pass up through the bore.
Heres a trick for the new clip so you can fit it in easily, find a tube about four inches long (usually something like a piece of 1/2 inch copper pipe works) that can fit into the clip portion of the bore and also pass over the upper piston shaft.
Then place the cylinder into a vise holding it by one of the union bolts screwed into the outlet mounted upright and install the new piston parts lubed with fluid into the cylinder.
Now fit the clip just into the end so it just sits square inside the top of the cylinder.
Now use the tube to push it down square till it just clicks into the groove at the bottom portion where it sits.
Then you can install the rubber cover boot washer etc.
So hows the bore look inside?? is it smooth?? and what was the condition of the old piston parts.

pikeslayer · Post by **pikeslayer** » Sun Jan 24, 2010 12:09 pm

The bore is pretty smooth, might need some emery cloth taken to it. Piston is all crudded up.

tz375 · Post by **tz375** » Sun Jan 24, 2010 3:12 pm

I'd stay away from emery cloth or anything else that is rougher than the scratches in the bore. Even 1500 grit is not good, plus it leaves abrasive in the pores of the metal.

And you don't want to make it any more out of round than it is. Maybe try a brass wire brush on your Dremmel to remove any corrosion above the surface. There are small master cylinder hones which your local auto brake guy may have. That's a better way to go.

The piston needs to be clean but it really only holds the seals and springs in place. The seals are the most important things here and they should probably be replaced. They come with a replacement piston as a rule, so that makes it easy.

Some pistons have flap valves in the end, and a new piston will fix any issues there.

pikeslayer · Post by **pikeslayer** » Mon Jan 25, 2010 8:30 am

Hey guys, will this work for my bike. Part number is slightly different.

http://cgi.ebay.com/ebaymotors/suzuki-g ... ccessories

Thanks

Post by **Suzsmokeyallan** » Mon Jan 25, 2010 10:08 am

Yes it will work for your bike and shows as the updated piston/cup kit number. The complete part number is 59600-45811 in case you wish to keep it on file.

Wayne Meuir · Post by **Wayne Meuir** » Mon Jan 25, 2010 10:12 am

What TZ said!!

I put a master cylinder off a 2001 SV650 Naked bike on my Buffalo and it works beautifully. $20 off Ebay.

Wayne