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Stuck caliper piston on a 4th Gen.


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Well, this caught me by surprise, I was putting new rubber on the bike in preparation for the Franklin trip when I decided I had plenty of time to give the calipers a refresh. So after the rear went on I pulled the caliper took it apart and sent it through the Ultrasonic. Everything looked good and came apart easy as I had rebuilt them all last year.

 

Put the new front tire on pulled the left caliper, everything went fine until I put some oak in place of the pads backed up by some 1/8 stainless steel plate made for this job and put my air hose where the banjo bolt goes and gave it some air. At around 50 PSI one piston moved, the way I do it is move the a few MM's at a time then remove a piece of the oak. Safer that way. Well I got up to about 100 PSI and threw in the towel, I grabbed a piece of stainless round bar I use and put it in the cup, it fit almost perfectly, I tapped it with a 2lb hammer just a bit, 2mm by my measurement back into the caliper, so I had finally gotten it  to move. I tried the air hose again, but no luck. Its sitting on my bench right now with some penetrating oil around the cup, but since calipers are designed to keep brake fluid in I'm guessing they are pretty good at keeping fluid out, so I'm not hopeful.

 

The only thing I can think of is reassemble and try to use the MC to remove it. I know from working on ships hydraulics are a force multiplier, but I have no idea how much a MC on a bike would produce.

 

BTW, thinking about why this happened, I remembered coming back from Madawaska last fall and running into some slushy and surely salty snow for about an hour, It was another 6 hours home and I forgot about it. I'm sure this is self inflicted.

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7 hours ago, FromMaine said:

 but I have no idea how much a MC on a bike would produce.

When performing a bleed test on a first generation BMW Integral ABS system you have to keep the brake pressure within a certain range for a couple of seconds. That's 7-10 MPa for the front and 4-6MPa for the rear.  With the VFR having a smaller diameter front brake MC the pressure will easily reach those figures.

Hydraulic brake pressure test equipment is rated up to about 20MPa/3000 PSI

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After once filling my garage with aerated brake fluid (which seemingly found itself onto every painted and plastic surface in there), I never, never, never use air in connection with hydraulic systems.  YMMV, but I think you're going to have to re-assemble the system, fill it with fluid and do it that way.

 

Ciao,

 

JZH

 

 

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Brake-fluid under pressure is also much, much safer than compressed air. That's because brake-fluid isn't anywhere nearly as compressible as air. At 2000psi, once the piston moves 0.5mm, all pressure is gone from brake-fluid. With compressed-air at that same pressure, it'll send piston through other side of caliper, through garage wall and into your neighbor's house!!!

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IIRC 4th gen OEM calipers are made by Nissin.  Was the point to switch to an upgraded Nissin version? 

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10 hours ago, JZH said:

After once filling my garage with aerated brake fluid (which seemingly found itself onto every painted and plastic surface in there), I never, never, never use air in connection with hydraulic systems.  YMMV, but I think you're going to have to re-assemble the system, fill it with fluid and do it that way.

 

Ciao,

 

JZH

 

 

 

8 hours ago, DannoXYZ said:

Brake-fluid under pressure is also much, much safer than compressed air. That's because brake-fluid isn't anywhere nearly as compressible as air. At 2000psi, once the piston moves 0.5mm, all pressure is gone from brake-fluid. With compressed-air at that same pressure, it'll send piston through other side of caliper, through garage wall and into your neighbor's house!!!

 

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I work on ships for a living, our 3 generators produce 1,100 kilowatts at 200 amps, this is shunted down to 220, 50 hz then various amps from 20 to 100 depending on circumstances, either will kill a man in his tracks. So we use a lot of compressed air, every locker on deck has an air hook up, we use it to lift hatches, run tools, the engineers must have a dozen in their work shop and our 2 16 cylinder Caterpillars as big as school buses use air starters instead of electric. I can't even imagine the DC voltage and amperage you would need to turn them, which in turn becomes dangerous if you come in contact with them. We have engineers 24/7 doing rounds/maintenance, so its the safer option, I'm used to it, wear protection, limit the movement to 3-4mm at a time and always have the trajectory pointed away from me or others. In short I'm comfortable with it. That said I did use hydraulics when I woke up at 4 am today and went to the garage. I'll explain later.

 

 

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1 hour ago, Magneto said:

I once spent 50 bucks for special pliers to remove stubborn pistons, then pistons turned out to be bad and cheaper option was to upgrade to Nissin calipers... just sayin’

 

42 minutes ago, Cogswell said:

IIRC 4th gen OEM calipers are made by Nissin.  Was the point to switch to an upgraded Nissin version? 

These are oem Nissin calipers, no upgrade needed they are excellent stoppers. Reason was to clean, teardown, inspect, grease pins, reinstall, thats all.

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I woke up at 4 am and headed to the garage, later the night before I had tried to push the piston out by blocking the good one with wood and pumping the MC. The pressure mounted but nothing happened and the handle went soft. So I looked around my garage, I have tons of parts, but mostly first Gen. Right next to the lift is my 86 VFR750, sporting Nissin calipers. I looked at the MC and it was smaller and different, even the banjo bolt is a different thread pitch, But i took it off any and mounted it on the 97. using the 86 MC with its banjo it mated to my hose perfectly. Bled the system, and when ready, had a go. The lever went hard the the piston finally moved. It only went until it was about 6mm from the exit hole then stopped. I let off the pressure and levered it back. repeat stopped in the same place. So I cleaned it with brake cleaner and 4000 grit emory at the end, coated it with brake fluid and pushed it back. Did this about 8-9 times. Had to take my wife to the Hospital for some tests at 7 am so cleaned up and left. got back to my garage about 1pm and repeat this procedure about another 20 times. I was pushing it by hand at the end, still not as easy as the other, but acceptable, then went in for dinner. It was mounted when I did. Spent the night with my wife, she has until noon off tomorrow so will spend the morning with her. Considering I had ben in my garage from 7am until 930 pm on Sunday, Mothers Day, missing family breakfast and an afternoon lunch, probably a wise move.🙃 I'll clean the right side tomorrow and bleed the system, take care of some small stuff and test ride on Thursday. 

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thanks for your post frommaine that was interesting timing .

I work in a trauma theatre and had a patient in today who thankfully just had a gentle off #wrist who had break failure they just serviced at the week end the culprit  was loose connection . 

 

Personally I would not accept any difference resistance on the pistons there the breaks essential stopping gear .

if the seals are hung up or there is something could have a catastrophic fail at any point.

 

my patient could have saved themselves the issues they have created for themselves by doing a long term compression test . easiest way to do it is wrap bungee round the break lever and handlebar holding break on measure distance from bar end weight screw to pen mark on lever end. go for cup of tea ( other beverages are available ) come back and check distance. if its the same its ok if its less there is something wrong . if its more you can't use a tape measure !

 

before you ride and check for leaver creep as this patient didn't 

 

anyway please be carful with breaks it could cost you your life and then who would look after your family ?

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Wasn’t my intention to suggest there is a bolt on upgrade for your particular bike, but to look for caliper option to buy on the the used market.

One of my bikes uses oem tokico  6 pots, Nissin 4 pots are popular upgrade. Performance improvement  is debatable but spare and service parts are way cheaper. 

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servicing the tubular slider pin under the rubber cover is mostly overlooked. needs to be inspected for rust, cleaned, and re-lubed periodically or brake won't be working its best.

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4 hours ago, MuppetGonzo said:

the patient mentioned this to me in conversation and asked me to warn my friends hence the post 

 

My father had missing portion of his ring finger and I engulfed myself in a ball of fire once. Talking about shop safety is always welcome. 

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6 hours ago, MuppetGonzo said:

thanks for your post frommaine that was interesting timing .

I work in a trauma theatre and had a patient in today who thankfully just had a gentle off #wrist who had break failure they just serviced at the week end the culprit  was loose connection . 

 

Personally I would not accept any difference resistance on the pistons there the breaks essential stopping gear .

if the seals are hung up or there is something could have a catastrophic fail at any point.

 

my patient could have saved themselves the issues they have created for themselves by doing a long term compression test . easiest way to do it is wrap bungee round the break lever and handlebar holding break on measure distance from bar end weight screw to pen mark on lever end. go for cup of tea ( other beverages are available ) come back and check distance. if its the same its ok if its less there is something wrong . if its more you can't use a tape measure !

 

before you ride and check for leaver creep as this patient didn't 

 

anyway please be carful with breaks it could cost you your life and then who would look after your family ?

Finished bleeding the system this evening and had my 3 heavy duty rubber bands (the type they use on lobster claws, this is Maine after all) on the lever before I came in for the night to read this. I'm well aware of necessity to double check, and test not just the brakes, but any maintenance done on the bike. I do appreciate you mentioning it though.

 

 For the record I am a tea drinker, have been all my life, PG Tips is my go to choice. Lived in Falmouth, Cornwall for almost a year back in 2015, our ship was dry docked at one of A&P's dry docks, but Pendennis did all the work. Bought a 91 VFR to get around on. Yard rules were we could not be on the ship when the yard quit work. So we had every Friday from Noon until 7 am Monday morning, unheard of as we are a 24/7 operation when running. I saw a lot of the southern part of England and all of Wales during that time, only missed one weekend because of frosty roads. Cornwall is much like Maine, small towns, strong fishing tradition, , rocky shores, lots of guys shipping out to make a living,, epic winter gales, over run by tourists in the summer and funny accents🙂

 

BTW, my wife has been a nurse for 45 years now, 25 straight in ICU, 8 in the Operating room and now Cardiac Rehab as she needed a break. I'm an expert at getting advice🙃

 

Michael

 

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3 hours ago, Magneto said:

Wasn’t my intention to suggest there is a bolt on upgrade for your particular bike, but to look for caliper option to buy on the the used market.

One of my bikes uses oem tokico  6 pots, Nissin 4 pots are popular upgrade. Performance improvement  is debatable but spare and service parts are way cheaper. 

Trust me, I am definitely in the market for replacements or alternatives. I assume you had to fabricate carriers for the Nissin 4 pots? If you could elaborate I would be very interested in reading what you needed to do. Many thanks.

 

Michael

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3 hours ago, squirrelman said:

servicing the tubular slider pin under the rubber cover is mostly overlooked. needs to be inspected for rust, cleaned, and re-lubed periodically or brake won't be working its best.

Pulled the last caliper out of the ultrasonic, let them dry, then hit both pins with my brass wheel. Always do, but doesn't hurt to see it posted for all to read.

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3 hours ago, Magneto said:

 

My father had missing portion of his ring finger and I engulfed myself in a ball of fire once. Talking about shop safety is always welcome. 

Your father was lucky in my book, lots of guys killed by wearing wedding rings, but also watches, gold chains, belt buckles, tools and one guy who was using his computer down in the engine room when something happened and 400 volts ended up at the receptacle. I've done26 Atlantic crossings, six in the engine room because of short manning. We were required to do an hourly walk through the engine room and inspect the engines Generators and record readings. I made sure I never had any metal on me, not even a few coins in my pocket.

 

Won't ask what happened but glad you are here to talk about it. We do fire drills once a month on the ship, some times without notice. All of us are also required every 5 years to renew our SOLAS certs, a week long set of courses that include 2 10 hour days in a full nomex suit, boots, helmet, gloves, full mask and a Scott pack on your back. I won' go into the details, but nobody went out for a drink after on those days. My garage is 12 X 24 and made of wood, even the floor. I have a fire extinguisher on one side mounted by my bench, then another on the other side near my parts racks. in between are my bikes, didn't want to be caught having to climb over or around especially if the fire was near the extinguisher. I am 15 feet from the house and we have 3 more in there.

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All good stuff FromMaine, I am glad they get you what is needed. Couple of years there was an arc flash that threw guy from a ladder and dented fire door, he survived with broken limbs. Nothing is routine around big stuff.  

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4 hours ago, FromMaine said:

Pulled the last caliper out of the ultrasonic, let them dry, then hit both pins with my brass wheel. Always do, but doesn't hurt to see it posted for all to read.

 

IMAG3734.jpg aye

 

IMAG3743.jpg

 

 

IMAG3742.jpg

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Update:

 

After 12 hours went out to the garage and had a look. The lever had not budged a mm from the night before. No leaks everything seemed fine, removed the bands and pumped the lever, plenty of room between the grip and lever when pulled in hard. I had the bike elevated so I gave the wheel a spin. felt a little resistance, but there are new pads upfront so I thought they might just have to seat. I decided to remove the left caliper and see how the wheel spun, it spun freely. So I removed the pads and started pumping to see if one piston dragged while doing so. I pumped until the end and they both fell into the plastic basin below at the same time. At no point was there any resistance at the lever. While waiting for the fluid to drain I was trying to figure out why there was so much resistance the day before. I looked into the bores and they were perfectly clean, no corrosion. The seals were intact and seated properly. I removed the caliper and put it on the bench and took out the seals, the grooves were shiny like new. I threw the metal parts in the ultrasonic and had a think.

 

No idea why I had issues at first, when I finally got the piston to move and could not remove it when it was almost out, well maybe it was not as straight as I thought it was, or some unknown operator error on my part. All I knew is that I now had a functioning caliper in front of me. I put everything together, bled the system in about 5 minutes  and gave the wheel a spin. It was better, but I still could feel a tiny bit of intermittent drag. I'm going to leave everything as is and test ride it in the morning on a short ride and see if it settles in.

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