Any tips for front caliper re-assembly?

[7911special]

The pistons came out only with using grease, wouldn't budge on air. Everything is clean but I can't believe how tight the piston to bores without an o-ring is. There is no pushing the piston in by hand without an o-ring.

I've had the o-ring stretching on some cans, as if I try to put them in there out of the kit, they almost fall out of their grooves. I am stuck trying to get the piston past the new rings, I am using a c-clamp right now, but it gets really tight at the o-ring.

I also tried using a pop can like a shim, that allowed me to get the piston in without pushing the o-rings down, but the can tore when removing.

Car calipers are stupid easy compared to these right now.

[IanDMacDonald]

I'd guess the groove the ring sits in is dirty/corroded. There are great threads on here regarding caliper rebuilding

[bikerphil]

1. Are you sure you have the correct caliper seals, ones for the Standard are 4mm smaller diameter smaller than for the Special. 2. Are you using brake fluid as a lubricant? 3. As mentoioned, make sure there is absolutely no crud in the seal grooves.

[7911special]

Grooves are clean, it is like the o-rings are smaller, ie there isn't a "wrinkle" in the o-ring as if it wasn't full diameter. Checked PN at Bikebandit for my order, shows Yamaha 1152491.

Yes on Fluid as a lube.

[WMarshy]

Grooves are clean, it is like the o-rings are smaller, ie there isn't a "wrinkle" in the o-ring as if it wasn't full diameter. Checked PN at Bikebandit for my order, shows Yamaha 1152491.

Yes on Fluid as a lube.

It's hard to confirm you have the right part number on my cell but I would double check you have the correct kit. As mentioned by others, the specials are different from the standards. Sounds like you have the wrong one to me, they should slide right in no questions asked.

[bikerphil]

Might want to measure the ID of the caliper seals, Specials should be about 42.5 MM, the Standards are 38 MM. What is the condition of the pistons, is there any pitting?

[cajun31]

Hey 79

how do the new rings that you got in the kit measure up to the old ones you removed?

[jacked_72]

On mine, the groves behind the oring were crudded up. I had cleaned everything and then had to use a c clamp to get them back in and of course they continued to hang up. I wound up having to scrape off the crap (looked like scale) with a pick and screw driver. I used the old orings and the pistons went in with gentle hand pressure. If you've got doubts about the new orings, try the old ones. If you can get the piston in with finger pressure, then it is probably the wrong orings. If you can't, I'd go through the groove again and make sure the build up is gone.

[WMarshy]

Cant really consider it a cleaning until you clean the groove behind the o-ring. That is the source of all piston sticking problems. Like you said, get it clean and you can usually reuse the old o-ring and they slide right in.

[WMarshy]

The pistons came out only with using grease, wouldn't budge on air. Everything is clean but I can't believe how tight the piston to bores without an o-ring is. There is no pushing the piston in by hand without an o-ring.

I've had the o-ring stretching on some cans, as if I try to put them in there out of the kit, they almost fall out of their grooves. I am stuck trying to get the piston past the new rings, I am using a c-clamp right now, but it gets really tight at the o-ring.

I also tried using a pop can like a shim, that allowed me to get the piston in without pushing the o-rings down, but the can tore when removing.

Car calipers are stupid easy compared to these right now.

Sounds like you need to clean the bore of the caliper with a fine grit flap wheel. You can make your own with some emry paper and a split manderal or go buy one at Harbor Freight. The piston should have a reasonable amount of clearance such that it should drop in without the o-ring. Sounds like you have some crud build up.

[MPittma100]

Caliper

I have come across some nasty calipers in the past. I find that media blasting the piston and o ring area with glass bead works very well. Only removes crud, no aluminum material. Caliper interior also looks like new. All of the ones that I have cleaned in this manner are working properly and not leaking. Piston slides in and out with no problem.

If you choose this method, you must be sure to remove all glass bead residue before assembly and it is a must to protect the threads for the banjo bolt and bleeder screw.

Mike