AJP Brakes

[beta_trials]

Ok guys what is the best way to get the cylinders out of the caliper on the front brake of a 95 or 94 JT 160 gas gas. I need to get them apart to see if i need to rebuild them or see why they are sticking so bad. one piston is completely stuck and the other sticks at a certain point and will not retract all the way 100% of the time. Here is the weird part though. the piston that doesnt retract all the way is the inner piston. If i lay the bike over to the right well past 45 degrees or so the piston begins to function properly for the most part. I have a feeling i will have to rebuild the caliper but i need to see whats happening first. What can i do?

[1oldbanjo]

I have plenty of experience with stuck caliper pistons in cars.....maybe some of it will help you with your bike.

I would first start by removing the caliper from the forks and taking the brake pads out while leaving the brake hose attached - then pump the brake lever until the pistons come out as far as possible. Then remove the brake hose and take the two caliper halves apart. Generally when rebuilding calipers I can get the pistons out by just using a compressed air nozzle on the caliper. Take the two halves and wrap a rag around the caliper so that when the piston comes out the rag will catch the piston and the brake fluid.....then apply the compressed air to the passage for the brake fluid and blow carefully (you may have to hold your finger over any extra holes or put a bolt in the hole where the brake hose attaches on the outer caliper half).

If that doesn't get the piston out another way is to use a grease gun. On the inner half you can use the bleeder screw to pump grease into the caliper - but you must plug/block the passage that routes the brake fluid over to the outer caliper. Blocking the passage can be done by inserting a thin piece of metal over the hole (between the caliper halves) and then bolting the two halves back together. You can also do this for the outer caliper but you will have to make a special fitting that will adapt your grease gun to the brake house inlet. If you have to use the grease gun method - be sure to clean all the grease off everything as the most seals are not compatible with grease and will swell when they stay in contact with petroleum products......and the brake shoes and disc don't benefit from having any grease on them!

Good Luck.

A

Edited December 15, 2010 by 1oldbanjo

[b40rt]

This tool is expensive but made for the job, ask Santa.

http://www.machinemart.co.uk/shop/product/details/laser-motorcycle-brake-piston-removal-tool

[richt]

I found a suitable RawlBolt that fitted inside the pistons tightened it up, then grip the rawlbolt in the vice and wiggle the caliper off.

[tltel]

hi

I had a siezed brake piston in my sons 94 gas gas (AJP same as yours)and tried several ways to remove it but found that the recess in the piston was tapered and nothing would grip it. compressed air wouldnt move it.

The previous owner had ridden it for a long time without a front brake and it was solid.

simple but drastic solution was to drill a 5.5mm hole in centre of the piston, tap a 6mm thread into piston, screw in bolt and it will push against back of caliper and out comes the piston, it actualy only took minutes to do and you get new pistons with the seal kit.

Obviously you must make sure you only drill through the piston and not into the caliper body.

TLTEL

[beta_trials]

Hey guys thanks for all the info. We were able to finally get both pistons apart and working properly. The seized one just had alot of dirt and crap that some how go in there but it is now functioning. Did not have to replace the seals. Will do that next time. Thanks again guys.