snowtrac brake master cylinder replacement issue

Greetings All:
To add to the general fund of knowledge:
If you replace the master cylinder in the ST4, you may run into the same issue I did. The hole in the master cylinder replacement was smaller than the original. While the pushrod dry fit OK, once in place the parts didn't want to fit together unless really stressed.

The pushrod is not a straight push. It starts out below the center line of the master cylinder and as the brake is pressed it moves to the cemterline and at full travel is slightly high. With the original part the hole in the piston was big enough for this "play" to happen. Troubleshooting the root cause took a bit.

My fix was chucking a 10.9 grade bolt the same size as the pushrod in the lathe, turning the head off and making the ball. Then turning a narrowed section where the interference hit the end of the piston. It has enough strength yet the reduced size lets it line up without binding.

Also for what it's worth. The NAPA replacement is longer than the stock and requires a slight amount of sheet metal work on the firewall.

what did the master wind up being?

VW bus or car?

redsqwrl said:

what did the master wind up being?

VW bus or car?

Click to expand...

bug was what I used. Use 1964 or earlier. must avoid the 2 circuit masters.
I don't know if the pre 64 bus was correct or not, I just used "bug"

an older bus fit mine. I took it in and they matched it.

I used the longer than stock NAPA single circut replacement for an early bug and notched some sheet aluminum to get it to fit. Works like a champ now for 4 years.

I do however wish the two band machines like mine had a good bit more braking capability. They work, but several times I wished they had more braking power than they do, even when they are in prime shape.

Probably the reason the newer machines moved the brakes inboard. Keep the snow and ice away, and they have a better higher capacity brake drums than the older ST's do.

Regards, Kirk