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Discussion Starter #1 (Edited)
What in the world?

Thanks for taking the time to help me out馃檹

My bike is a 2002 Suzuki GSXR-750 with about 8000 miles on it.

I've replaced:

Both front rotors - EBC floating rotors
Brake fluid - Autozone dot 4 (I think this might have something to do with it)
Brake pads - EBC Double H sintered metal pads
Relatively new front tire
CRG brake lever
Replaced 3/4 stock bleeders with Speed bleeders (Both front calipers have the speed bleeder. The rear has one speed bleeder and the stock bleeder)
Torqued every bolt to spec in my owners manual

I bed in the brakes for about 100 miles of gradual slow - fast stops towards the end of the 100 miles.

I'm having major issues with my front brakes

I caught pebbles between my right front brake a few days ago
Removed them yesterday to inspect
Cleaned the pad surface with a shop towel. Cleaned the calipers with brake clean

Used copper anti-sieze on the back of both pads
While pads were off I checked the rotor to see if the scratch caught on my nail and it did just barely (after test ride it has smoothed out)
Noticed the scratch pattern on the brake pads matched the rotor scratch
Put pads back and torqued caliper bolts to 11 ft lbs
Went for a test ride this morning and wow there's got to be an issue here.
I expect that it'll be rough until the scratch wears down but should it be really bad?

During my test ride braking at any speed causes vibration


When I use my front brakes the bike vibrates violently to the point where my mirrors shake
When I was parked it after coming back home I lost all pressure in my front breaks but was able to pump it back up to a point where the pressure felt strong

I can also hear the pads lightly touching the front brakes with the bike off and rolling it forwards and backwards
I noticed my brake fluid in the front cylinder is at the lower mark but when I bled them last month I know for sure I filled it to the upper level

My thinking for what might fix it:
  • Caliper rebuild (Will take it to shop. Don't have air compressor. Might get one if it's worth it). I've only seen John Tally from partzilla do this on YouTube​
  • Bleeding brakes with motul brake fluid (is the difference that great - headsmack if it is)​
  • My break lines have cracked and I need to replace them (will likely get Spiglers steel brake lines)​
  • One or multiple bleeder screws have vibrated loose and I'm losing fluid at one or both calipers​
  • I just realized I didn't check the the left caliper after going over that gravel/pebbles (also might be it. I'm thinking and typing)​
This one's got me stuck feeling like I need to take it in for repair but if I can avoid the shop gouging service fees, I'd rather work on it myself. Plus, I really don't like when I find out they stripped a screw or put something on extremely tight with power tools creating problems down the line.
 

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Both the vibration and the loss of brake action (you didn't lose pressure, you didn't have any) says bent rotor to me.

That would be the first thing I would check.
 

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Discussion Starter #3
Both the vibration and the loss of brake action (you didn't lose pressure, you didn't have any) says bent rotor to me.

That would be the first thing I would check.
Thank you for the advice. I'll remove the rotors and check them with a digital caliper and post back
 

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^ What he said. Actually, just holding something on the fork tube (i.e. a screwdriver) close to the rotor while you spin the wheel will give you a very good idea if the rotor is bent.
 

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You can set something as simple as a spray can on the floor VERY close to the rotor, and spin the wheel. You will clearly see if you bent the rotor. You still have the stock ones? hope so, because you are likely to be putting them back on...

A bent rotor will give you these same symptoms. the rotor will force the caliper pistons to retract far enough to where you will need to pump a couple times to get the pads to make strong contact with the rotor surface again. And of course will pulse and shake like a SUMBITCH...
 
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Discussion Starter #8
You can set something as simple as a spray can on the floor VERY close to the rotor, and spin the wheel. You will clearly see if you bent the rotor. You still have the stock ones? hope so, because you are likely to be putting them back on...

A bent rotor will give you these same symptoms. the rotor will force the caliper pistons to retract far enough to where you will need to pump a couple times to get the pads to make strong contact with the rotor surface again. And of course will pulse and shake like a SUMBITCH...
That was actually the problem before. The right rotor was bent and I had to replace them both. I bought the bike used so I expected it to have some issues. I always replace the brakes/rotors/tires whenever I get a "new" bike. Looks like I'll be going to cycle gear to pony up another $225 馃く. Thanks for all the advice. I'll post pictures of my findings.
 

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Discussion Starter #9 (Edited)
Alright. So I took the calipers off the left side today to inspect the rotor thoroughly. Not good news. The caliper pin that holds in the brakes was gone and one of the brakes was missing. That grinding noise was from the caliper pistons grinding against the rotor. The only thing I can think about is that I didn't screw the caliper pin in all the way. I doubt gravel could cause the pin to break. So I'm ordering a rebuild kit, a new rotor, and another set of pads.
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That will do it. At least you found the problem.
 
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S&P- HOly Guacamole!! I just read this post.
From the beginning there were some REALLY concerning things in your posts.
First of all- is a K2, with only 8K miles? You bought it with a supposed bent rotor? Have you ever seen the specs on how strong these brake rotors are? Yes, they can bend- RARELY. If it was bent, as in a crash, what else is damaged on the bike? Any Gixxer with only 8K miles should not need any brake work- period.

And lastly, you didn't bleed the left caliper? On the OEM set up, that's the last thing/area that gets the brake fluid in your system! By not bleeding that, the air there will get back into the rest of the system when in use. I would start at the farthest point in your OEM set up- the left rotor- it bleeds the Right mostly first., When it's no bubbles, then check the Right one for bubbles, then the Master Cylinder on the clip- ons.- Dont forget to bleed that one too.

Why did it need all these parts in the first place?

* Interestingly- I posted on my LiterBikes thread that when I recently did my own tire change- I found one of my caliper pins that holds the pads in missing too! The other one was there, and about to fall out. I didn't loose either pad luckily.
I had installed new EBC HH pads up front a few months before- so it was ME who tightened them last!
So I didn't have to wait for my local shop to order a pair at $25 each,
I got a pair from the cycle salvage across town- for $25 for the pair.

And lastly again- unless you are MM, VR, etc.- I don't think I would ever notice the difference between AutoZone Dot4, and MOtul, etc. Wasting your money IMHO.
And NO, I don't think the brake fluid caused ANY of your problems.
If you are in fact an advanced/expert track day junkie- by all means, spent the $$ for that.
Hell- I buy tires that are better than I can ride, so there is that.

Glad you found the problem. Check everything again, watch a few bleeder youtubes and get them bleed properly- very important. Almost as important as installing the parts correctly.
* And as I said, I inadvertantly found one of my pins gone too! I had put it in last too!

Stay safe.
Have we seen pics of this 750? I'd/we'd love to see some pics!
 
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Discussion Starter #17
S&P- HOly Guacamole!! I just read this post.
From the beginning there were some REALLY concerning things in your posts.
First of all- is a K2, with only 8K miles? You bought it with a supposed bent rotor? Have you ever seen the specs on how strong these brake rotors are? Yes, they can bend- RARELY. If it was bent, as in a crash, what else is damaged on the bike? Any Gixxer with only 8K miles should not need any brake work- period.

And lastly, you didn't bleed the left caliper? On the OEM set up, that's the last thing/area that gets the brake fluid in your system! By not bleeding that, the air there will get back into the rest of the system when in use. I would start at the farthest point in your OEM set up- the left rotor- it bleeds the Right mostly first., When it's no bubbles, then check the Right one for bubbles, then the Master Cylinder on the clip- ons.- Dont forget to bleed that one too.

Why did it need all these parts in the first place?

* Interestingly- I posted on my LiterBikes thread that when I recently did my own tire change- I found one of my caliper pins that holds the pads in missing too! The other one was there, and about to fall out. I didn't loose either pad luckily.
I had installed new EBC HH pads up front a few months before- so it was ME who tightened them last!
So I didn't have to wait for my local shop to order a pair at $25 each,
I got a pair from the cycle salvage across town- for $25 for the pair.

And lastly again- unless you are MM, VR, etc.- I don't think I would ever notice the difference between AutoZone Dot4, and MOtul, etc. Wasting your money IMHO.
And NO, I don't think the brake fluid caused ANY of your problems.
If you are in fact an advanced/expert track day junkie- by all means, spent the $$ for that.
Hell- I buy tires that are better than I can ride, so there is that.

Glad you found the problem. Check everything again, watch a few bleeder youtubes and get them bleed properly- very important. Almost as important as installing the parts correctly.
* And as I said, I inadvertantly found one of my pins gone too! I had put it in last too!

Stay safe.
Have we seen pics of this 750? I'd/we'd love to see some pics!
Thanks for taking the time to read my post! I changed the rotors because I was told that the left rotor was warped by the shop. It failed inspection because of this. So i swapped both out along with new pads. I know for sure I torqued everything to spec. I didn't use blue Threadlocker on anything but the rotor bolts. I watched a few John Tally and Sportbike Track Gear videos on how to bleed brakes. I started with the master cylinder then the right caliper then the left caliper. After the master cylinder and both front calipers were empty I put on the speedbleeders and kept the master cylinder topped up as I pumped the front brakes until I saw there weren't any air bubbles, no old fluid and the lever felt firm. Same deal with the rear. Empty, changed stock bleeder for speed bleeder. Filled with new fluid keeping it topped up until rear pedal felt firm with no air bubbles in the bleeder tube. It was fine up until I rode the bike in the driveway with all that gravel. I was at a loss for what the hell happened and just rode it below 60 home along with engine braking and made it back
 

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Hope you and'or your bike wasn't injured.
I thought you posted that you had forgot to bleed the left caliper?
Anyways, I hope you get'r fixed. Lets see some pictures!
 
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Discussion Starter #19
Hope you and'or your bike wasn't injured.
I thought you posted that you had forgot to bleed the left caliper?
Anyways, I hope you get'r fixed. Lets see some pictures!
Whoops! Re-read my post and corrected. I was talking about checking the left caliper after the going over the driveway with gravel. Thanks for pointing that out.
 

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Discussion Starter #20
FINAL UPDATE

Ordered a new set of pistons/seals from ebay:

Took the right front caliper off the bike

Needed to get the pistons out. They were in the bore all the way. Saw John Tally pop them out using an air compressor. If you clicked the link for those pistons you know I didn't have the cash to buy an air compressor. Talk about expensive habits...I digress. I figured the science of it is all the same so I used a spray can of air and a microfiber cloth

Covered the bleeder valve with my thumb and the banjo bolt opening with my index finger and stuck the straw for the compressed air in the gap where the fluid flows and they shot right out

Seals were worn. There was gunky fluid all behind the pistons.

Cleaned with brake cleaner and wire brush and old toothbrush
Put brake fluid in the bore, wet the seals with brake fluid and placed in bore, put new lubed piston in bore
Repeat with smaller piston
Changed the small seal where the brake fluid enters the caliper (tiny seal near the top)
Put the caliper back together
Put thin coat of copper anti-sieze on the back of the brake pads
Put blue threadlocker on the brake pin
Took off damaged rotor
Put on new rotor- blue threadlocker on the rotor bolts - torqued to spec 16.5 ft lb
Put caliper back on the bike
Bleed front brakes. Still had some of that amber gunk in the system
Bleed the rear because I had the time and fluid. Bit of amber gunk in there too
Babied the front brakes for about 100 miles between parking lot, street, and highway riding


All problems with the front brake are now fixed.
This forum is really something special. I'm appreciative that there are people kind enough to help out other riders. Thanks for all the help everyone!
 

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