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If you are attempting to push the caliper piston deeper down into the caliper make sure you remove the master cylinder fill cap first. Watch for overflow at the master cylinder with the cap off as you push the piston down in the caliper. Better get some rags or paper towels handy, just in case.

R.E.A.R.

Good point, Bob! A baking pan beats a pool of red fluid on the shop floor. Even shoving the piston .025 into the caliper can move more fluid than you think! Ted

Was able to find some .001 stainless steel aircraft grade washers locally to shim the two halves from each other. It only took two to get things adjusted properly.

What is the "correct" fluid to use in my brake system? can I use conventional automotive brake fluid? I currently have clear DOT 3 Synthetic in the system but can easily flush it if necessary.

Alan,

Airheart systems used what is called a 'red' or mineral based fluid. It is used in aircraft and can be found at a company called Aircraft Spruce. They sell pint and quart bottles.

https://www.aircraftspruce.com/catalog/ ... ey=7846362

R.E.A.R.

Air heart used both types of fluid. My understanding is they have different seals. I would go with what ever was in it originally.

With Tolomatic no longer being interested in the kart systems, they no longer sell the seals for the brakes. You must be able to find which fluid the system originally used so you can keep from mixing them. You might get lucky and find rebuild kits for both master cylinder and caliper so you have known seal compounds. A brake seal blowout at speed can be a disaster. The engineering group at MCP now supplies master cylinders and calipers with seals that'll handle multiple fluids. I have at least a quart and a half of Airheart "Red" out in the shop that I will never use. Ted

All seals for a rebuild of Airheart systems are available on line or at a 'seal' distributor. You will also be surprised how inexpensive they are.

Just purchased some myself and I got them in Buna rubber and they work great. I was in question about how the seals would react to my fluid of choice so I threw the seals in a glass full of fluid for a day and see if they swell, distort or even melt.

My comments are my personal experience and in no way are a endorsement or recommendation for anything. You are on your own rebuilding brake systems.

R.E.A.R.

Hey, Bob, Pruit went through the master cylinder cup thing a few weeks ago. I know he got several that had the right diameter and material, but the wrong shape. I guess he solved it, but it wasn't simple. I think he ended up turning the piston to fit the cups he found. O rings are oh-so much easier! Ted

It's not an o-ring. If I remember right it's an "X" ring or something like that. Not round. Not square it had corners & low spots in the middle. Think it was for the master cylinders.

Also had a kart with very old fluid in it. It kinda dried out & was sticky / thick. I put as much new fluid in it as possible and blead the brakes & let it sit for a few weeks & came and changed it out again with fresh fluid. After that no problems.