92 VFR rotor replacement caliper problems

Discussion in 'Mechanics Garage' started by jimmy.miller.969952, Jun 9, 2014.

  1. jimmy.miller.969952

    jimmy.miller.969952 New Member

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    So, I have to apologize for no pics up front... Last post I got the tip that "without pics this thread is worthless".... Unfortunately I use my phone light for mechanic work so my camera takes the most blurry pics you've ever seen.... Anyway, 1992 VFR750 just purchased.... Ordered new rotors and replaced today... Rotors went smoothly without a hitch; however, when I went to install new brake pads I ran into caliper issues... The manual says that pistons should push in easy and if not then service caliper... Called and got a quote on full caliper service (keep in mind I've been riding this for a month and brakes work great with no leaks (just worn rotors).... Called last owner who said to use a tool to decompress pistons... Since I have experience with this on dirtbikes I put the old pads in place and used a C clamp to compress the pistons in the caliper until I could get pads on and fit onto bike.... I got them onto the bike without any problems but they make a rubbing sound when I spin the wheel... I am a novice mechanic and I love my bike even though its old.... I want to be sure that I am not doing any damage if I run it this way... Should I take the calipers back off and try and compress the pistons further (I didn't wanna overdo it the first go around and cause problems)? Also, what is the proper procedure for bleeding the brakes and putting new fluid in? Thank you for your help! These forums are a HUUUUGE help and I appreciate every bit of advice.
     
  2. nearfreezing

    nearfreezing New Member

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    First of all, that rubbing noise isn't normal and since these are the motorcycle's brakes, definitely park the bike until you straighten out the issue. It's not safe to ride until you know what the problem is.

    It sounds like one or more of the pads is not seated properly. I would try taking the calipers off and remounting the pads. How easily did the pistons retract? They should have retracted with pretty minimal force. After you remounted the caliper, did you give the brake lever a few squeezes to seat the pads to the rotors?

    You might be interested in purchasing a shop manual for your bike, like this one:
    http://www.haynes.com/products/productID/473
    The OEM one might be available somewhere like ebay or online.

    Edit: if you were able to install the caliper with the pads, you compressed the pistons sufficiently.
     
  3. jimmy.miller.969952

    jimmy.miller.969952 New Member

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    So the pistons would not retract very well with hand force... I had to use a c clamp and then they went with moderate force (basically by hand they barely moved but with a c clamp they moved relatively easily).... I did not want to over crank on them so I used medium pressure on the c clamp... I was able to reinstall the calipers with new pads onto the bike... but when I spin the front wheel with my hand I hear the rubbing noise... There is no pressure in the system at this point the lines aren't even connected... Tire seems to spin freely. I had one friend tell me I could pay him 2 hrs labor and buy new seals and he'd rebuild it, but I really don't wanna throw away 150 dollars on labor if I don't have to...
     
  4. nearfreezing

    nearfreezing New Member

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    In that case, the rubbing noise is probably just light contact between the pads and rotor, that should be ok. When everything is put back together and the brake fluid has been added, there shouldn't be any noise because the seals will retract the piston, allowing the pads to push away from the rotor.

    I wouldn't rebuild the calipers unless they're leaking or the seals/dust shield are obviously worn.
     
  5. REEK

    REEK New Member

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    I tend to have a different opinion on caliper rebuild. If I don't know the status or last rebuild on an old caliper, I will order the seals and rebuild it. I don't know this is absolutely correct on motorcycles, but I push the pistons in all the way when I change the pads and they should move with ease. on a 92, I'd bet its time for caliper service. If your lines are off and if you're going to put new lines on, why not refresh the calipers too?

    servicing them is not a really big deal. pump out the pistons with air or brake pressure. I usually split the calipers - means ordering one additional seal/o-ring. remove all of the old seals. clean, clean, clean! some times I use 1000 grit sand paper for stubborn residue on the pistons. clean some more. "lube up" the new seals with brake fluid. Some people I've heard use some special fancy super expensive lube. slide in the clean pistons all the way. re join the caliper halves. I'll usually throw on some new speed bleeders at this point. add on your new steel braided (?) lines. after that you just need to bleed and add pads. Might consider a master cylinder rebuild too if it's the original 92 master.

    please take the above with a grain of salt. I have a little OCD when it comes to braking/stopping.

    And if your friend wants to charge you $150 to help out, you might want to shop for a new friend when you order your seals.
     
  6. ridervfr

    ridervfr Member

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    Oh! Brake fluid ane anit-freeze, my favorite things to get on my hands.

    You need to do a thorough brake service, which means; taking calipers off each side, and figuring oot how to use the brake lever to push the pistons oot! Once you have them oot, you have to do a good cleaning behind the seals, don't use anything super sharp as you dont wana score up those channels where the seals go. You can clean the old seals and re-use with no problems. I have a nice pair of internal c-clip pliers I use on the inside of the piston to get it oot of its bore. Once everything is done, with a little brake assembly lube or just DOT4, those pistons should go in nice and easy.

    Your problem stems from the "smigma" behind the seals, this is not letting the pistons retract. If your not comfortable doing this type of work, a shop should charge aboot 2 hours labour. Anyway, if I had a friend, :sad: and he wanted to charge me $150 I would punch him in his bread basket
     
  7. jimmy.miller.969952

    jimmy.miller.969952 New Member

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    Thank you for the help! I'll let you know what I end up doing
     
  8. jimmy.miller.969952

    jimmy.miller.969952 New Member

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    So I ended up installing the calipers with new pads the way they were.... to compress the pistons I put the old pad in against the piston and used a c clamp... I cleaned the pistons while they were out and they went in without much problem... I ordered a seal kit but had several people tell me it is normal to use more than hand pressure to compress the pistons... Looks easy enough to rebuild, so i'm going to ride it locally for a week until I get the parts and then clean out the calipers... Test drove it yesterday and it braked no problem.... Also the rub is gone now as far as I can tell! Thanks for your help... I'll follow up once I do the rebuuild
     
  9. ridervfr

    ridervfr Member

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    Good, I love happy endings and no loss of riding time :vtr2:
     
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