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Post by taint on Apr 6, 2008 19:10:22 GMT
It never rains but it pours  I'm having a lot of fun overhauling my rear caliper. I'm trying to replace the seals and replace the lines with Braided; however it seems that aside from replacement pads, no one has serviced this caliper since day one. One of the pistons was seized, both pistons are rusty and both bleed nipples sheared when I attempted to loosen them.  I managed to remove the two pistons; admittedly one using a pair of mole grips  . Thankfully I'd already ordered replacement pistons and I have replacement bleed nipples. However, I don't know how best to remove the remains of the bleed screws. Both screws sheared just below the line of the caliper; so there's nothing to grip onto. I tried using screw extractors which made no difference; aside from destroying the screw extractor. I've started to drill the screws out, but I'm getting worried that I'm going to go right through the other side. It really is a worst case scenario  Any thoughts? T. |
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Post by cam7777 on Apr 6, 2008 19:51:09 GMT
I'm in the same situation as you, only answer is another caliper IMHO
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Post by taint on Apr 6, 2008 20:57:54 GMT
Ick, now that's something I didn't want to consider. Pretty much nothing on Fleabay atm, and the caliper is useless unless I can get those bleed screws out.
I've drilled out the centre of the screws and I've managed to thin down the walls, I'm wondering if I could crush two of the sides together then use a pair of needle nose pliers to 'extract' the rest. I may have to drill thinner still; I've used a 5mm drill, I may go to a 5.5 or 6mm as long as it doesn't hit the threads.
T.
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Post by amorti on Apr 6, 2008 21:55:39 GMT
Keep trying as you have nothing to lose, but if you drill too deep and mark the nipple's seat, it won't seal. Time to find a replacement caliper, really. I don't much want to touch my rear brake, I must admit!
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Post by amorti on Apr 6, 2008 21:58:54 GMT
You could always drill a bit bigger and tap it out to an M8 bleed nipple. Again, as long as the seat remains untouched, which gets to be a tall order.
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Post by beeblemaster on Apr 7, 2008 9:00:07 GMT
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Post by General Gman on Apr 7, 2008 9:49:34 GMT
Any engineering shops nearby with a spark eroder ?
Always used to use the one on the shopfloor where I worked years ago - brilliant bit of kit.
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Post by taint on Apr 7, 2008 9:51:51 GMT
I'll give that a try tonight Beebs, I'll just need to find something that will fit. As I mentioned, I've tried the screw extractors and all they've done is make a mess Cheers T. |
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Post by taint on Apr 7, 2008 10:17:16 GMT
Ok Gman, I've done a Google search and I'm still no clearer on what a 'Spark Eroder' is.  Any clues T. |
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Post by General Gman on Apr 7, 2008 11:55:08 GMT
It's a beastie what engineering shops use to remoce broken taps etc. We had one set up by our radial drill section cos nutty nigel always tried to drill / tap 4" holes too quickly in stainless steel impellers.He was king of the broken tap. Proper name for the beastie is and EDM machine - explanation here: www.eod.gvsu.edu/eod/manufact/manufact-277.html |
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Post by andyc on Apr 7, 2008 11:59:54 GMT
I would use a stud extraction tool.
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Post by taint on Apr 7, 2008 22:07:35 GMT
Right, one trip to the local motorcycle garage/breaker and I'm a couple of steps further sideways. I was berated for not coming in sooner; apparently If I'd come in before I'd begun drilling, they'd have welded a nut onto the tops of the screws. Not owning a welder, I hadn't thought of this They recommended the hammer in square type screw extractors rather than the counter threaded type I'd been trying. (I've found a local supplier for these) They also found me a replacement caliper body. Not from a diversion, but nigh on identical with one less bleed screw. The body is in a relatively good state, but the caliper is in a horrific state; It'll need a fair bit of work to get it into a usable state; the pistons are just a rusty mess and the faces, which are normally pressed together are furry, (for want of a better word); however the mechanic was kind enough to remove the old rusty bleed screw BEFORE he sold it to me. So £10 later and I still have a lot of work in front of me Looks like I'm going to have to Steal my Dad's Dremel  Cam, if I manage to get the old bleed screws out and clean up the other caliper; you'd be welcome to the spare. Cheers T. |
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Post by darren on Apr 7, 2008 23:01:13 GMT
They also found me a replacement caliper body. . you should have asked if they knew what it was off, would be usefull info |
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Post by taint on Apr 8, 2008 9:22:17 GMT
They told me and it's written on it; but I've neither had it to hand or remembered what it was both times I've posted. My memory can be appalling at times  I'll try to make a note when I next pick it up. T. |
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Post by taint on Apr 8, 2008 21:14:03 GMT
Right, That's fsck'd it  One screw extractor later and I'm pretty sure it's not going to fix . The stump you can see in the picture is the sheared end of a brand new Proto square screw extractor. There's not really enough there to get a pair of mole grips on, so I think it's permanently shot. I tried heat, I tried hitting it with the hammer, but in a test of strength the remains of the bleed screw won. Anyone know someone with a Spark eroder? Cause I don't In other news, the other caliper is from a Yamaha TZR 250; they're basically an identical caliper which uses the same brake bads (FA104). The only difference is the single rather than double bleed screws. T. |
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Post by neilmud Lord Protector on Apr 8, 2008 21:25:56 GMT
Isn't that something stuck in the middle of the screw maybe thats why your having trouble getting it out
;D
Neil
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Post by taint on Apr 8, 2008 21:33:44 GMT
Ya think? ;D |
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Post by taint on Apr 9, 2008 21:35:37 GMT
Ok, WD-40 is great stuff; it's already managed to get most of the carp off the replacement caliper, and I'm leaving it to soak in; as the pistons are seized solid.
Looks like someone may have tried removing them before; as the pistons appear to have residual weld material at the bottom. There was also a fair amount of copper grease on the outer faces of the pistons.
I may have a little problem with the new caliper. The caliper splits into two pieces, held together by two bolts. Pressed between the two faces is a rubber grommet which seals the two halves and allows the brake fluid to pass to the second piston.
The original caliper has a single hole and grommet, but the new caliper has two; most likely because it only has one bleed screw. This becomes a problem; because the new caliper didn't come with the grommets and I only have one from the original.
Looking at the Yamaha parts diagram for the Diversion caliper, they don't break the caliper down into its component parts; so they don't list these grommets.
Does anyone know where I can get these sort of parts?
Cheers,
T.
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Post by m40man on Apr 9, 2008 21:56:45 GMT
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Post by taint on Apr 9, 2008 22:31:00 GMT
Thanks for the response m40man, not quite the same type of washer, but may be an ideal replacement. I've ordered a pack as that's a decent price for a bag of O rings. I can try hitting halfords as well; I think a flat rubber washer may also be an option; assuming all of these are suitable for use with brake fluid. Of course, all of this is pointless if I can't get those pistons removed I'll update if I manage to find a suitable alternative or if I manage to extract the pistons. Cheers T. |
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Post by taint on Apr 10, 2008 9:10:00 GMT
Looks like there's a fair number of yamaha motorcycles which use the FA104 brake pads, some of the smaller bikes use them for the front, but there's also a fair number which use them on the back. I recon it should be possible to use several of these calipers as replacements. Take a look at this tinyurl.com/547673The caliper is basically identical to the diversion. I'd need to check that it uses the same piston kit, but should otherwise be a straight swap. T. |
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Post by beeblemaster on Apr 10, 2008 9:33:47 GMT
Only problem with that particular one tho is that (if the pic is correct) then the caliper fixes to the caliper bracket from the left hand side.... with the Divvy it's on the right |
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Post by taint on Apr 10, 2008 10:23:06 GMT
That's on the right too; unless I'm getting it totally ass backwards... Unless you mean the outside and inside of the mount arm. In which case, I'm not certain if that'll make a difference; as I'm pretty sure the diversion caliper is threaded too; which probably means it should mount on either side of the arm. Either way I'm lost ;D T. |
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Post by taint on Apr 10, 2008 10:51:27 GMT
Thinking about it, I'm pretty certain my new caliper is threaded, but I can't remember if my D6 caliper is. So I may have to drill out the threads anyway.
T.
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Post by amorti on Apr 10, 2008 14:36:25 GMT
Trev on here has a Special Trick for getting out stuck pistons using a water pressure testing machine at his work. Wish I could remember his username.
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Post by eliminator on Apr 10, 2008 20:09:04 GMT
If you want to pay for the return postage I'll blow it out for you. I use a pump that will go up to about 1000 psi, and pump enough water through, so that if the seals are damaged and leaking, it will still pressurise the piston.
Although the phrase, horse / door / bolted springs to mind.
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Post by taint on Apr 10, 2008 21:16:00 GMT
Thanks for the offer Eliminator, I may take you up on the offer; dependant on whether the WD-40/piston pliers work.
It's not like I care about the old pistons and seals ;D
Cheers
T.
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Post by eliminator on Apr 17, 2008 18:54:17 GMT
A week has passed, what's happening.
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Post by taint on Apr 18, 2008 21:08:49 GMT
Hi Eliminator, There was no success on the WD-40/piston pliers front; even after I decided to light the residual WD-40 in the caliper and let it heat through. Aside from getting it sooty it did nothing to help move the pistons. At the time of the last posting, the caliper was in two pieces and would not have been air/water tight for pressurising. I've had to wait for parts to arrive; so that I could put it back together, but it is now in one piece. On top of all of that, I've had an emergency server replacement and two funerals I'm going to have a word with my local garage tomorrow morning, to see if they can blow the pistons with their air compressor, if not I'll definitely need to send it to you for the higher pressure water treatment. On a side note, I've acquired a third calliper; which is in a much better condition than the other two, so the pressure is off to a degree. Course, I still need to strip and clean that one as well; so I may just have let myself in for more problems. I'll update you tomorrow and assuming no success, I'd be very grateful if I could send the caliper for pressurising. Cheers T. |
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Post by taint on Apr 19, 2008 21:12:40 GMT
Well, the garage were closed by the time I got there; so no real help. On top of that, trying to remove the bleed screws on the newer caliper, one sheared and the other removed. Even though I was being really careful it sheared very easily. I'm really not having much luck with these. I'm going to take the newest caliper to Breaking point and get them to weld a nut onto the remaining screw. As for the caliper with the stuck pistons, Eliminator, if you PM me your address, I'll get the caliper in the post with the cost of return shipping. T. |
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. Thankfully I'd already ordered replacement pistons and I have replacement bleed nipples.
