PA50 Brakes Being Iffy

I recently got my PA50 up and idling again, thanks to you guys, but now I've run into another problem. The front brake has no problem at all and has about 6-7 mm of play, which is about where I like it. The rear brake, however, is giving me problems. When I spin the wheel, it stops as if the brake is constantly engaged. This happened all of a sudden, actually, I was tightening it to where I wanted it to be, and accidently went too far, and this started to happen. I can loosen the brake cable on the wheel and fix the problem, but doing that causes more than 15 mm of play in the handle, which is way too much for me, and is more than what the manual says. Any ideas as to what the problem is? I've been playing with it almost all day, and nothing has come of it :(

Re: PA50 Brakes Being Iffy

the brake assembly's return-mechanisms are kinda weak .. there are two shoe-springs inside .. These plus the light spring on the cable's end are supposed to completely open the shoes. But if there's any brake-shoe cam friction or if the cable is not well lubed and free, the brakes won't open as wide as they can.

Take the rear wheel off the bike.

Remove the large "nut" (with only 2 flats) on the freewheel sprocket side.. It comes off counterclockwise, like any normal nut. (this "nut" is actually the freewheel sprocket's hub and it all comes off in one piece.)

This axel-nut thing can be really hard to remove. You'll probably have to fix a wrench on it tight fit ..and strike the wrench end firmly with a hammer to break it loose.

:

Next pull the brake assembly out. It's center is a bearing so wiggle and pull the assembly off by hand.

Now you can clean up the shoes and brake drum. Use some fine sandpaper on the shoe and drum surfaces to remove rust and glaze ..

Then lubricate (all purpose grease) all the moving points in the brake assembly.. the cam and brake shoe-ends where the cam is and the shoe-pivot ends. Don't get any grease on the shoes/drum surfaces .. don't use so much extra grease that it could fling off and get on them either.

Reassembly is easy.. reverse what you did. Torque the axel nut to about 45 pound feet (600 kg-cm)

Next the cable should be lubed.. drain some oil down the sheath.. like hang the cable vertically by it's end and drip oil into it.

If everything moves easily, you can adjust the rear brake to grab hard after only 3 or 4 mm of brake-level free play... and the brakes wont drag at all.. i know because mine do it.

Re: PA50 Brakes Being Iffy

It sounds like tthe rear brake drum rusted up while it was sitting. As you adjust it you suddenly come up against the rusted high spots.

Do like joew says and all should be right with the Hobbit world.

Re: PA50 Brakes Being Iffy

Thanks guys. I started doing what you said today, and things were working out fairly well, I didn't see any rust, but quite a bit of brake powder. However, a new issue was discovered: whatever is on the other side of the brake mechanism (where the belt connects with the rear wheel) is leaking oil. It doesn't happen all the time, but I can see that it has been coming out where the two parts of that side connect (it's darkened) and when I turn that piece to one side, it starts leaking out fairly quickly. I should probably replace that oil, but I'm not even sure what that other thing does...

Re: PA50 Brakes Being Iffy

That is a reduction gear and in/out gearbox. You flip the lever to pedal the bike wihout driving the engine.

If the seal is leaking it can put oil on your brake linings. Not a good deal.

Re: PA50 Brakes Being Iffy

don't worry about the oil leak until you're sure its a gasket or the filler bolt.. and not just leaking from the vent in it's backside..

Whenever the rear wheel is off the bike keep the gearbox upright (there's an up-arrow stamped on it) I tie it to a spoke so it cant rotate.

See attachment.

1121213848_gearbox.jpg

Re: PA50 Brakes Being Iffy

btw, the oil is regular old SAE 90W gear oil (or maybe 80W90.. whatever.. doesnt really matter) and you fill it till it comes out the filler hole when the bike is on the centerstand.

Re: PA50 Brakes Being Iffy

Awesome. That doesn't sound like such a hard thing to replace, however, I should probably do that now that some has spilled out, eh? I just went down and set it on its side so that it's facing the right way. Now that it's leaked, is there any need to open it up and clean anything in there, or should I just pop everything back together and fill 'er up with oil again. Thanks!

Re: PA50 Brakes Being Iffy

Don't open the gearbox .. I did it on one of my spare wheels just because i wanted to see what it might take to modify the gear ratio.

There be springs, loose caged roller bearings, spacers, and an assortment of gears that will disconnect, jump or fall out when you open the case.

Oh yeah.. and guaranteed that gasket is stuck on both sides and you'll tear it to shreads.. I think i'm pretty good at carefully opening cases and preserving stuck gaskets but this one was near impossible.

Re: PA50 Brakes Being Iffy

Hahaha... okay, won't be doing that then, I'll just find some oil and fill 'er up, to be safe. Thanks a lot!

Re: PA50 Brakes Being Iffy

Hrm. I went to 2 different places, and all I could find in the way of gear oil was 80W90, when the manual calls for SAE 90. Is that okay? Neither place had SAE 90 :(

Re: PA50 Brakes Being Iffy

80W90 will be fine.

Just squirt it in the filler hole until you can't get any more in there.

Re: PA50 Brakes Being Iffy

Souuuuunds good, thanks a lot guys. I'm not going to empty it or anything, I'll just add this stuff on top of whatever was already in there.

Re: PA50 Brakes Being Iffy

i tend to doubt myself and my memory sucks so last night i looked in the '83 PA50 manual from mopedriders.org.. It says add 75cc of gear oil.. nothing about filling till it overflows.

So i put 75cc in an empty gearbox and the level came right up to the filler bolt hole and a tiny bit came out..

:

Multiweight oils (like 80W-90) just means the oil is thinner (80W) when the oil is cold. But when at operating temperature a 10W40 is 40W .. and a 80W90 is 90W.

"Lots of boring info":http://www.advanceautoparts.com/english/youcan/html/ccr/ccr20010101ov.html This allows better pumping and lube distribution while the cold engine or gearbox warms up.

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