Airheart Brake Bleeding

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Alan Lewis
Posts: 18
Joined: Mon Jun 29, 2020 1:11 am
Vintage Karting items owned: 1967 Bug Sprint Kart with MAC 91-C
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Airheart Brake Bleeding

Post by Alan Lewis » Fri Mar 12, 2021 2:07 pm

Wondering if there is a particular sequence to bleeding my brakes, top or bottom bleeder first? I had a hard pedal before emptying the system but can't seem to get one now. Am I missing something else. I seem to be getting all the bubbles out of the system, but still no pedal, and no leaks.
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REAR
Posts: 978
Joined: Sat Jun 16, 2007 10:19 am

Re: Airheart Brake Bleeding

Post by REAR » Fri Mar 12, 2021 4:09 pm

Alan,

It is good to bleed the master cylinder first with the brake line hooked up to it to make sure your getting fluid to the caliper.

You can check if you have fluid at the caliper by pressing and holding the petal while cracking the compression fitting at the caliper. If you have fluid at the caliper go thru a couple of bleeding cycles slowly so the fluid has a chance to fill the caliper. Use the top fitting for bleeding.

If you are using 'RED' mineral fluid be careful, that stuff eats paint.

Put a small cotter pin or safety wire through the roll pin that holds the pivoting master cylinder actuating arm to the master cylinder body. Good little safety precaution.

R.E.A.R.

ted johnson
Posts: 1577
Joined: Fri Jun 15, 2007 7:59 am

Re: Airheart Brake Bleeding

Post by ted johnson » Fri Mar 12, 2021 4:24 pm

Alan, you need only to use the upper bleed screw. Some guys tape a small bottle of fluid to the rear of the kart, lower than the caliper, and put a piece of model airplane clear fuel hose on the bleed nipple, and submerge the other end in the fluid. That way, you push the air out of the caliper and it rises to the top of the fluid in the bottle, and when the pedal returns, you don't have a risk of sucking air back in. TJ

Alan Lewis
Posts: 18
Joined: Mon Jun 29, 2020 1:11 am
Vintage Karting items owned: 1967 Bug Sprint Kart with MAC 91-C
User Agreement: Yes

Re: Airheart Brake Bleeding

Post by Alan Lewis » Fri Mar 12, 2021 6:43 pm

Thanks guys, will give that a shot. I was trying to bleed them using both bleed screws, in no particular order, and I didn't bleed the master first. Appreciate the safety tip on securing the roll pin.

REAR
Posts: 978
Joined: Sat Jun 16, 2007 10:19 am

Re: Airheart Brake Bleeding

Post by REAR » Sun Mar 14, 2021 9:53 am

Alan

Upon further review of your brake system it is advised to replace the copper brake line with the plastic brake tubing.

Reason being is that karts 'flex'. Solid brake line may flex but at some point it is going to break and that could have catastropic results.

As far as the plastic tubing goes it was offereed as OEM equipment from Airheart in their brake kits so it is true vintage.

R.E.A.R.

Alan Lewis
Posts: 18
Joined: Mon Jun 29, 2020 1:11 am
Vintage Karting items owned: 1967 Bug Sprint Kart with MAC 91-C
User Agreement: Yes

Re: Airheart Brake Bleeding

Post by Alan Lewis » Sat Apr 03, 2021 8:59 am

:lol: Now I have the opposite problem. The brake caliper seems to be locked on the disc before applying the pedal for some reason. If I ease the two nuts that hold the two halves of the brake caliper together slightly, I can turn the axle by hand and then apply the pedal to get the caliper to actuate and grab the disc. How can I get enough travel so I can bolt the two halves back together tightly? Once again, thanks for the help. And, yes I did replace the copper tubing with plastic.

roger santee
Posts: 83
Joined: Mon Jan 28, 2008 7:58 am

Re: Airheart Brake Bleeding

Post by roger santee » Sat Apr 03, 2021 5:55 pm

You can make shims to go between the two halves. This is standard practice.
Airheart use to sell them. I don't know of anyone selling them. I make my own.

ted johnson
Posts: 1577
Joined: Fri Jun 15, 2007 7:59 am

Re: Airheart Brake Bleeding

Post by ted johnson » Sat Apr 03, 2021 6:46 pm

Alan, sometimes this works, sometimes not. Take a couple of .025 feeler gauges, loosen the caliper bolts and put the feelers between puck and disc. Tighten the bolts back down. Often, when you take the feelers back out, the disc will be free. Cheap to try! Of course, the best solution is to buy a Wilwood caliper. They stop better and smoother. They have front and back pistons so the disc is fixed to the axle. Ted
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Alan Lewis
Posts: 18
Joined: Mon Jun 29, 2020 1:11 am
Vintage Karting items owned: 1967 Bug Sprint Kart with MAC 91-C
User Agreement: Yes

Re: Airheart Brake Bleeding

Post by Alan Lewis » Sun Apr 04, 2021 1:34 pm

Thanks for the suggestions guys. Ted, I'll attempt the feeler gauge trick tomorrow, and hope for the best. If that doesn't work, I'll head down to my local hardware store and search for some spring steel washers to shim the two pieces out from each other slightly Roger.

ted johnson
Posts: 1577
Joined: Fri Jun 15, 2007 7:59 am

Re: Airheart Brake Bleeding

Post by ted johnson » Sun Apr 04, 2021 3:35 pm

Alan, it's more stable to use shims the shape of the caliper to ensure the outer half of the caliper can't rock. You can get brass sheet in various thicknesses from a hobby shop. It's easier to cut than steel sheet. Good luck with the feeler gauges. The trick worked on my old 175 caliper on my Bug Black Widow. The caliper has a "drag ring" on the movable piston. Sometimes putting feelers in and tightening the bolts can reposition the drag ring, resulting in the piston retracting properly. Here's a cross-section of the caliper. Look at item No. 6. It is the drag ring. Ted
http://mail.tolomatic.com/archives/pdfs ... CDB_ps.pdf

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