Suggestions for popping the brake calliper piston

So, I have read and read about the various ways to pop the piston in the great threads on here but I am in a spot of bother and would love some suggestions if possible. Bikes are XJ650 4K1. I have 4 sets of calipers that are old and need a rebuild. One method that I am unable to use is the existing brake fluid and lines as they had already been removed from the bike and were sitting by themselves. Compressed air is not an option either as I don't have an air compressor. I don't have a pulling tool but I do have a grease gun.
Grease guns can generate a ton (or up to 4500psi) so should have enough but according to threads on here (and I can already imagine )will be really messy when finished. As I understand it, the bleed nipple for the caliper is designed to let air and fluid out. when fully tightened it is designed to block any fluid from escaping but when loosened a 1/4 turn will allow fluid (and air) to escape. I don't think they are designed to allow grease into the caliper but the nipple itself is a good fit. My grease gun will not thread into the caliper brake fluid line. So would I need to get an actual grease nipple of the same thread size as the bleed nipple and pump the grease through there?

 

@Jetfixer uses a grease gun to remove pistons. He will know how to connect it. He will see this alert.

 

Thanks @Franz

 

just found this thread...https://xjbikes.com/forums/threads/difference-between-brake-bleeding-screw-and-grease-fitting.36150/
I think I need to do something similar. Perhaps the bleed screw is chock full of rust and crud.
Will give it a crack tomorrow.

 

i've used several methods, including the grease gun and air.
but by far the most reliable method, and least messy, is to use the original master cylinder ,and a brake line, to push them out.
put the master cylinder and lever, in a vice or workmate, atatch the brake line, and fill the sytstem with brake fluid and bleed a little , you dont have to bleed every last bit of air out.
then simply push one piston out , then push it back in with a G clamp, (make sure you push it back in squarely, by putting a socket in the piston well)
then push the opposite piston out.
once you've got them moving, you can push one piston completely out, then use an old brake pad with a piece of rubber between and the G clamp, to seal the hole.
then push the other piston out.
it sounds complicated but once set up, its easy , and you can do all your calipers, the same way, at the same time.

getting grease out of all the passageways, uses loads of brake cleaner

 

Hey bensalf, Thank you! Unfortunately I don't have any brake lines either. When I bought the bikes they were pretty much dismantled into a load of boxes. but no brake lines (which is good in a way as I assume they would have been the original from 40 years ago). So perhaps I should look at getting some new ones. The grease gun is not ideal I agree but it seems my only route at this point. Or I just bring them to a shop and have them worked on. But that defeats the point of me doing the rebuild . When you have done it before did you use the bleed nipple? I am contemplating using some thread tape on the bleed nipple so it doesn't need to seat right down and has a good seal.

 

I did my XJ700 with air in the bleed screw hole. Unscrewed the bleeder and used a rubber tipped air gun shoved into the hole.

 

I guess id need a compressor for that. Although its probably a good investment.

 

This might work with a simple car tyre inflating compressor. Car brake caliper is bigger though.

 

Thanks Franz! managed to pop it using the bleed screw and a grease gun. The bleed screw just needed some cleaning to free up the bleed channel in the screw.

 

Any comments on the quality (or lack thereof) of the piston and bore? To my untrained eye they look like they just need a good clean. No noticeable gouges or damage.

 

Clean it first so it can be inspected.

 

Great they are out. Clean them and make sure there is no pitting and they should be good to go. Pitting can damage the new seals.

 

Good call. will do

 

@Franz thanks for the tip. will clean them up and have a good look.

 

Post some pictures once they are cleaned.

 

Affirmative

 

Hope these photos show the pitting on the caliper. photo 474 shows pitting on the face of the piston, 475,476,477,478 shows pitting on the sides. and 479 shows inside of caliper bore with brown crud. I don't have scrapers that can get that stuff off just yet. But I think the inside of the bore looks ok, thankfully.

 

Making my own assessment...the piston needs replacing.

 

Yes I would replace them too. Look pitted and scored in places.

 

Thanks Franz, new rebuild kit needed me thinks.

 

Get new hoses too if you can if you have the original Yamaha ones. Nothing more important than brakes.

 

yeah, new hoses for sure. the bike didn't come with any. Goodridge are apparently up to scratch

 

pulled apart the 4 calipers. There's a fair bit of brown gunk in the caliper bore of each and some on the pistons. I think I have 2 usable pistons. The other two have a bit of pitting in them. Any suggestions for cleaning off the brown gunk?

 

Clean the grooves the new seals will sit in too. Try a soft brush and some clean brake fluid. If that doesn't work try a brush and brake clean.

 

So, I had 2 what I thought would be good pistons. But Im thinking I really only have 1. Or should I say bugger it and just get 4 new replacement kits and not chance it. Thoughts from the brains trust please. the first two photos are from piston 1 (Needs replacing due to that one little pit??). The last photo is from the one piston that I think is still usable? Any thoughts? Thanks all.

 

Thanks Franz. Ive cleaned up the pistons. now onto the calipers. should I soak them in the brake fluid?

 

Just clean the bores with clean brake fluid and a cloth or soft brush. If you have access an air line you can clean the brake line and bleed nipple openings on the calipers.

 

Looking at the pictures the pistons are not pitted near the seal so l would use them as the pits cannot tear the seal. The pads will prevent the pits getting near the seal.

On reflection l would replace one just to be sure. The second one looks fine to reuse.

 

Thanks Franz. Will give that a shot tomorrow. Im disappointed that I can reuse more of the pistons but as these are the parts of the bike that make it stop, I guess its important that they are in full working order. Three replacement pistons are the order of the day. I don't have access to an air line yet so will resort to lots of brushing as best as I can.
Thanks for the advice sir!

 

I will be doing the same once l assess what my calipers are like as my bike is off the road at the moment.

 

i use a piece of scotchbrite, scourer, cut to shape, to fit in the grove, then chase it round with a blunt instrument, i would reuse the pistons in the pictures, they're not that bad, flat the "pits" down with some 1000 grit wet and dry, so they dont rip the seals.

 

Cheers Bensalf. Was wondering how to tackle that groove.

 

Since your in OZ not sure where you would get them , here Harbor Freight has bristle wheels that you can chuck in a drill will make cleaning easy .

 

I got a multi tool which has some brass bristle wheels. Haven't had a chance to get stuck into them yet. Also gonna try the scotchbrite suggestion from Bensalf