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GS 450 spongy front brake

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My sons 81 GS 450 had a slightly spongy front brake. I took the caliper off and sure enough the pads are very low so I installed new pads. It's still spongy and now it drags. There are no leaks and the piston moves freely in and out. I Put a known good master cylinder on it - same thing.I have not taken the caliper piston out, but I'm guessing there is corrosion in the bore and a bad seal?? I have a spare caliper apart on the bench but the piston is pitted. Thoughts??
 
Not to state the obvious but I assume that you bled all the air out. When we rebuilt the master cylinder on mine a couple months ago, it took forever to bleed the sponginess out of the brake.
 
When I did the front brake on my 450 I replaced the line with DIY stainless lines and fittings and a Suzuki caliper rebuild kit. Made a world of difference.

It did take for-ev-er to bleed all of the air out of the line.

This was two years ago and its still doing fine. Probably due for a overhaul, for piece of mind rather than mechanical failure, but its still solid.
 
If you still have the rubber front line on there, get rid of it in favour of a braided line, there is no comparison with 30+ year old rubber.

I ended up strapping my lever to the 'bar over night and the next morning it was nice and firm.
 
I concur with replacing the rubber line. I put the braided on a few years ago and I won't go back now.
 
The caliper is dragging a little bit. I am absolutely positive I have all the air out. I see Zuzuki still offers a piston/seal kit for just under 30 bucks. I am going to my dealer to order that. Where can I get ready to bolt on stainless hoses??
 
Go onto eBay and search for suzuki GS stainless steel lines. You'll eventually run across a seller from Canada called Rennsport Auto. I recommend them. Good quality lines, quick turnaround, and _very_ reasonable prices.
 
Big +1 on Rennsport for the line.

And yes, get the piston set from Suzuki, quite inexpensive for a critical item like the front brake.
 
OK, I found Rennsport. It looks like they custom make each line to order. It asks for what size banjo bolt/fitting. What size is the GS 450? Also, looking at my GS 550 ( 1980 E ) the caliper looks like it may bolt on? If have spares for the 550!
 
I can't seem to find the information but I know Nessism has recommended an online store that allows you to purchase the individual parts, banjo bolts, compression fittings, stainless line, rather than a pre-made kit. I'm not sure how much the pre-made kits run, but I think for the individual parts it was around $30-$40.

It's incredibly simple to put together with basic tools, and the company had several how-to videos.
 
Rennsport has a toll-free number, or you can message them through eBay. It might be worth asking them if they have the measurements for your bike already. If not, they will certainly be able to tell you how to measure them. I've also seen people just mail in their old brake lines and let Rennsport clone them.

EDIT: I went the make-your-own-lines route for my front brakes since I'm a DIY person and was trying to save a few bucks. While some people have had good luck building theirs from hose and fittings, I personally wouldn't recommend it. In the end, I didn't really save anything compared to just buying the lines outright. Plus, I'm much less confident in my abilities to build a correct brake line compared to the people who've already done hundreds or perhaps thousands of lines.
 
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I called them and they are making what I need to match the lower bars my son has on the bike so the hose will fit perfectly an not be scrunched up near the bars. Also we went with red. As soon as I put new bars on my 550 I will be doing that bike too!!!
 
you are going to be very pleased with new SS brake lines. Just did the swap the other day. it's a MASSIVE improvement over the stock lines. you get way more feel and more bite on the disc when stopping hard.

i'm looking forward to hearing how it pans out.
 
Well, after trying everything I could think of I FINALLY found the problem and it left me scratching my head! I happen to have a brand new brake lever and compared it to the one on the bike. The difference is the contact area was worn down a LOT!! I tossed the new lever on and BINGO!! Works great. The new stainless lines are goining on in a few days!!
 
I always bleed them in reverse. Get a big syringe and some tygom that fits the end of it and over the bleed screw. Take the reservoir cap off and strap the lever to the bars. Now force fluid, using the syringe, in through the bleed hole up into the system and into the reservoir. It follows the path that air would wan to follow. Conversely you can used vaccum to draw fluid up to the reservoir, same effect. Always works for me, just did it in fact on the EFE and brakes are rock hard.
 
Once you get consistent pressure with a spongy front brake, tie down the brake lever as tight as you can get it. It will self bleed over night. Much easier than bleeding a million tiny bubbles and wasting brake fluid.
 
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