whats the trick for getting caliper piston in

On my 81 and 82 650 maxim the pistons were stuck inside the calipers.The 81 had been sitting and so i decided to use the caliper off the 82.Its front brakes had been moving before.I used a grease gun and got the piston out of the 82 caliper.I used one more container of grease on the other one and it just did not seem like it was ever going to get loose.So,now I have cleaned everything.The grease makes a huge mess.I got the caliper rebuild kit.It came with 2 thick orings and 2 thin ones.It was a kit compatible with different models.I see the thicker gasket fits in the groove of the caliper barrel.I had to use a pick to get the old one out.The new one just doesnt go into the groove and stay there.It even sticks out a little.I am thinking the piston going back in will keep it in place and also force the gasket to expand a little to get up in the groove and stay there.I tried putting the old piston back down with no seal in place, with it in place, neither works.I plan on using grease on the piston and maybe it will slide down.I know I can also use a c clamp.But, what is going to prevent it from catching on the gasket that is sticking out slightly from the groove,pulling it out of the groove,making it drop down into the barrel> I think if I put some of the heavy black grease on the gasket groove the gasket might go in there and stay put. Both the old piston and the new replacement one are both quite tight and neither goes willingly down in the hole.It needs to be this tight for correct operation, but I am at a loss.I can make it go down in the hole just as i made it reluctantly come out of the hole.I am afraid of catching the new gasket.What do I do?

 

Did you thoroughlly clean the piston seal grooves?
Did you lubricate the new seals with brake fluid?
What brand rebuild kit is it?

 

I got the piston in.I used a little motoroil on the outside of the piston and I used some grease to hold the seal into the grooves,I am still not sure that happened.I used a c clamp.The piston was very reluctant then finally it gave in and I was able to use the clcamp and get it down easily after that.I have put the through bolt in, the pads in their respective slots.ran the long bolt up through the caliper to where the 12 mm nut on top can be installed.There still is a little daylight between the caliper and where it snugs up against the forks.On an exploded drawing I dont see that there should be another washer or anything on top of the caliper between it and the forks.Its like the caliper is at a very slight angle,not completely seated across the fork leg on the bottommost portion.But it is completely as it should be on all other areas.I am curious what happened to that seal as I forced the piston down in the hole.I hope it didnt come out of the groove or I have just wasted a huge amount of time. K and L brand

 

Anything other than grease specifically formulated for a hydraulic systems should not be used. They can cause the rubber to swell and possibly brake lock up.

Cleaning the groove as k-moe suggested is very important, and using just brake fluid as a lubricant to assemble is also OK, although the red rubber grease designed for hydraulic systems makes assembly a bit easier.

 

If you have to use a c-clamp to get the piston in something is wrong. You can damage either one by doing that,
After cleaning the caliper and piston, test fit it. It should slide in easily with NO force needed. Then install the new seals with lube. Lube the piston and it will go in with hand pressure, turning the piston while pushing it in helps not to snag the new seal .

 

I used a c clamp, it went in.It did not slide in easily and it for sure did not come out easily.I used some black grease made by valvoline synthetic blend made specifically for bearings,brake components, cv joints and so on.Plus the amount was very minute.Once i got past about 1/4 inch in the piston went in easily.if you have ever done disc brake pads on a car you know that to apply even pressure on a caliper piston you lay a block of wood or a wrench across the opening and use a c clamp to compress it.I dont have any compression washers and all the dealers are closed on mondays so i will have to wait till tuesday to see how bad I messed up if at all.Usually I do.This piston reminded me of a tappet i struggled with on the other head I bought for my parts bike.For weeks i could not get it in.once I got it perfectly aligned and using both thumbs to guide it practically fell in.I would be surprised if the brake works but hopefully it will.

One question, what is the trick to keep the rubber seal in its groove while passing the piston by it.I used some grease to hold it in place, but I hope i didnt pull it out by snagging it with the piston.I have another caliper if i screwed it up.I know the piston keeps them in place once the whole thing is assembled,no way for the seal to come out then.

 

the SEAL has to be in BEFORE the piston is put in.No way around that. My fingers are crossed.

 

There should be no need for excessive pressure placed on the Caliper Pistons to replace them back into the Caliper Body outside of normal use of the C-clamp when Caliper Piston is pressed into a Caliper Body which has no build-up to cause the circumference of the Seals to be reduced. (I pasted this from our forum)

 

Read carefully. I said to test fit the piston first to make sure it fits in the bore easily and does not bind. Them remove and install the seal.

 

I stand corrected.Sorry.

 

I was told to just stick to one thread.My pipes the guy cut off right behind the heat shields.I have a set of stock exhausts and mufflers.Those things weigh a lot.I can get some shorty mufflers for about $60 for the pair.or even cherry bombs designed for a car.it wont be stock, but I am afraid of breaking off a bolt.I am not a purist but the shortys are almost as loud as the cutoffs.If you werent going with stock pipes and didnt want a 4 into 1 what would you use?

 

The seals should stay in the groove without the use af any grease. Are you sure that you bought the correct seal kit? From who did you buy it?

 

its made by k and l.I dont remember which company.It may be the wrong seal.the piston is identical.the seals look the same more or less.the one I removed was 37 years old.The new one wont stay in the groove. It will stretch and go in the groove, but sticks out when let go of.It was supposed to fit multiple bikes.probably because multiple bike models have the same brakes.

 

Hi ,a question regarding the front brake on my 81 Yamaha xj 650.i cannot get the brake to be very effective,I renewed master cylinder seals,first,new pads ,no fluid leaks, but spongy feel on leaver could bleed daily getting a little air out,
I would like to drive it but not confident
Breaks not what they should be,
Any help would be great.thanks

 

Please start a thread for your issue.

 

There's the problem. K&L make some really good parts, but they have a few things that just aren't correct.
Start a conversation with Chacal. He will have seals that fit correctly.

 

sounds like a good idea.the piston looks good though.shipping costs are ridiculous.

 

If you used motor oil on the seal or petroleum based grease I strongly suggest you throw them out and get new ones and thoroughly clean the calipers.
The rubber used on brake systems will react very poorly to anything oil based. They will swell and leak or jam up.
Either way not a good scene.
Only use grease designed for brakes or just good old DOT3.

 

ok

 

if I remember correctly the seals are angled. with the thicker part going to the back of the caliper, so it has to be the right way round.