Re: my Paso - a never ending (love) story ...
Posted: Sat Dec 31, 2011 12:29 pm
Thanks, Terry that is what I thought. Puh, then I didn`t forget it ... 
Being the only parts on the whole bike I didn`t strip I did that with the brakes, too. Even though rather simple I wouldn`t recommend this to anyone who isn`t sure about what he`s doing. It`s unnecessary in most cases, too!
The 907ie/851 calipers:
To get the pistons out I used a thin steel plate with an old sock over it. A piece of wood will be fine, too. The thinner the better as the more the pistons will come out the easier it will be to remove them.
Better wrap a rag around the nozzle to prevent brake fluid to be sprayed all around. If a piston doesn`t move out enough try spraying some WD40 in the gap, wait and press it back in; by hand or with a screw clamp. (In case of a screw clamp put some rag under not to scratch the housing).
Try again, if it doesn`t move more than before try again and push it in and out until it comes out. If the calipers are fine such a problem won`t occur.
The four bolts removed, the calipers split, o-ring saved. The pistons can be pulled out by hand with some wiggleing. Do not use pliers as chances are very high you will damage the piston.
Each cylinder has two seals. A larger one on the inside and a double lip one as dust seal.
Use a needle or a very thin screwdriver in a flat angle to get in the seal groove and lever it out carefully. Don`t pinch it if you don`t replace it and don`t slip and scratch the cylinder wall!
If reusing all parts store them in brake fluid and don`t let them dry as you may have problems when assembling.
The newer type Brembos. Basically the same but with different sized pistons for better brake response.
After the calipers were removed and the brake fluid was drained, the brake lines were secured to prevent any fluid getting on the rims or fender.
A rear caliper from another bike. Internals always the same; two seals per cylinder and an o-ring.
If one pistons is seized the other one will pop out so you can secure this one with a screw clamp and try again. A thin piece of wood should be put inbetween so the piston won`t hit the screw clamp in case it does finally move. This one didn`t. The only way to get it out is to attach it to a brake or clutch pump and try it hydraulically as this`ll create a much higher pressure.
The rear brake caliper. Being the old type it has only one seal in the cylinder and a dust seal plus two o-rings. Other than on many car brake calipers there`s no spring to secure the dust seal which eventually will punch a hole in it when trying to get it off. This seal comes off very easily. It`s important it is ok and not rottened dry as entering brake dust may cause piston seizure sooner or later. In worst case the brake will lock or become smoking hot. (May not be bad to replace these even though they look ok. Afterall they are from 86)
The rear brake pump. Don`t remove the plastic ellbow if it isn`t really necessary, you`ll just mess up the paint and mark the pumps surface.
Remove the rubber boot and the circlip. If you don`t have circlip pliers use a thin screwdriver put it in the circlip groove, in the gap between its two ends and try to lift one end out of the groove. If that works use some flat pliers to pull this end towards the other and it will come out.
If the piston doesn`t come out it`s because the washer has rusted and is sticking to the housing.
Do NOT try to hammer anything through the opposite side to push the piston out as there`s only a very tiny hole ! Spray some WD40 on the washer and use a thin stick (nothing sharp) to push the piston in and out until the washer comes loose.
As some were unsure when rebuilding their clutch or brake pumps... The larger side of the seal always has to show inwards or it won`t build up any pressure. (Maybe it helps the ones to remember if thinking of a parachute
)
All parts were rinsed inside and out to avoid any damage by the brake fluid.
The parts after their ultrasonic bath. In case the pistons have a dirt edge on the outer side you can use NEVRDULL or some other polishing wadding to remove it. If you ride very little and the brake pads are worn the pistons don`t retract as far into the caliper as they would with new pads. Theoretically the dirt building up on this "overhang" could ruin the seals over time if the pads are replaced with new ones which will push the pistons farther into the caliper again. Plain theory
In general it is NOT necessary to do all this, specially if the brakes don`t leak. I did it with every single bit of the bike so it would`ve been inconsequent not to do the brakes, too.
All internals of the calipers were clean just the brake pump (like most clutch and brake pumps) had some crystaline build up.
As no caliper leaked I`m reusing all the seals. (Except to the rear - non Paso - black caliper which will need a total rebuild). Also I split two sets of front calipers as I`m having them powdercoated from gold to black. I never liked my black rear with the newer golden front calipers. I wonder how they will look when finished.
G.
), and G. improves his bike where possible), but with this aim I`ll need more than a year...
