Master Cylinder Dust Boot

[Diablo007]

Any tips for getting the master cylinder dust boot over the piston?  Currently working on an RD350 master, but have an RZ350 not far behind that will need to be done also.

[1976RD400C]

I just did a couple of these. It ain't easy. Use 2 very small screwdrivers and treat it like you would mounting a tire. You need to get one finger on it to hold it down, then a screwdriver through the hole, and like a tire iron, lever it to start it on. The screwdriver will catch in the groove of the piston and hold it. Hold that in place. Then the other screwdriver through the hole to keep going, like mounting a tire. The thing is you must have a finger on it and push to hold it down as you're doing this. Do not try to push the rubber with the screwdriver tip, lever it through the hole. One that's on use something blunt to push the OD in place.

[forexer]

use a petroleum based product like Vaseline or I used Dow Corning DC 4 Electrical Insulating Compound which makes the rubber easier and more pliable to work with otherwise there's a chance the rubber will tear

Good Luck!

[Diablo007]

Thanks for the tips.  I use mineral spirits to soften old hard rubber parts.  I'm wondering if it will work for the dust covers.

[Diablo007]

Correction, not mineral spirits but lacquer thinner.

[pidjones]

Correction, not mineral spirits but lacquer thinner.

Use carefilly! Lacquer thinner (acetone) will swell and destroy rubber if left on for extended periods. I prefer temporary softening in hot water or with a heat gun.

[m in sc]

real lacquer thinner doesn't have acetone in it. that's that new 'compliant' bullshit. home depot sells real lacquer thinner that wont eat rubber.

i usually use a deepwell socket to push the boot and ring down, think an 11mm? cant remember. I tend to oil up the sides so it wont tear.

[Diablo007]

Thanks for all the great tips!  I had tried hot water before and failed.  I had even used grease at the same time.  The socket trick is so obvious that it wasn't.  If you get what I'm saying.  I was thinking finding something with a taper to put on top of the piston, never though about finding something just big enough to push it over the top of the piston.

I also didn't realize there were different lacquer thinners.  I'll need to check the labels before I buy now.

[m in sc]

this briefly explains the laquer thinner debacle:

https://www.woodshopnews.com/columns-blogs/its-a-struggle-working-with-new-compliant-solvents

JASCO brand laquer thinner in the all blue can without the yellow compliant label is also acetone free.

https://www.lowes.com/pd/Jasco-128-fl-oz-Fast-to-Dissolve-Lacquer-Thinner/50298081