81 Special Project

[mschor]

I'm starting a new thread to keep all this info together.

Trying to bleed the rear brakes. Bench bleeding the rear master I should feel some pressure at the brakeline fitting hole when I push the piston in, right? I don't feel any pressure, so thinking I need to rebuild it.

Separate question about petcock: Without the towers, no reserve? Screens are torn in a couple places but I have inline filters. Reserve should still be functional, right?

[Radioguylogs]

Rear Brakes

It sounds like you are opening the bleeder screw and feeling if there is pressure in the bleeder screw opening while you press the master cylinder.

In this circumstance, you would normally feel some pressure and some brake fluid might leak out around the threads of the bleed screw- clean it up before it damages the paint on your caliper.

If there is no pressure and no brake fluid coming out of the bleeder screw when you actuate the master cylinder, then most likely there is air in the line. Folks have various ways to 'prime' the line. I like to put a tube on the bleed and suck the fluid through. After the bubbles escape in the tube, you can blow the fluid backwards to push remaining trapped bubbles up to the master cylinder. This action works better than is sounds (no jokes please).

After you get a good prime, you can bleed the system normally.

I doubt you need to rebuild the rear MC.

Petcocks

Regarding the petcocks, you will have no reserve if you don't have a tube sticking up in the gas tank (simple).

[mschor]

Thanks Mike, I was trying to prime the MC off the bike because I was unable to pull much fluid through the line with a vacuum pump. I read here and elsewhere that if you take the MC off and cover hole in the MC where the brake line attaches with your finger it's a good way to prime the MC when other methods fail. I'd much rather just pull it through the line, but it doesn't seem to be happening. I expected to feel some pressure at the outlet hole as I pushed the piston in, but didn't so thought it might not be sealing well -Mike

[TopCatGr58]

Hey Mschor,

Okay, inline filters are actually better than the petcock in tank screen filters, so having some tears/holes in the screen filters is OK, and leaving them on the petcocks provides you with the varying height tubes to provide the RESERVE function.

Have you read about the Spooge hole for the MC's, it may be clogged, but it usually prevents fluid from RETURNING to the MC after it's pumped out, so now that I think of it, probably not the problem. Yeah, could be the piston seals are damaged and so not developing pressure. I remember reading about if the piston is pushed too far in the cup can flip/fold it's edges and then won't be able to make pressure. Sounds like you may need to take it apart to see what's wrong. Good luck.

T.C.

[mschor]

Thanks, I did take it apart and clean it good, but I'll do it again, make sure everything is on right. I think the previous owner said it had some rear brake problems before, so I may just put some new seals in it. Thanks for confirming the petcock reserve thought. I picked up the fuse box you sent in the mail yesterday, so that'll be next!

[donebysunday]

rubber line

Most likely not your problem but years ago I could not get a front caliper to work. I tried many things then found that the inside of the rubber line had become de-laminated and tore leaving a flap to fold over inside the line blocking fluid flow.

[mschor]

I put all new lines, I think it may be the spooge hole, I was careful about that on the front, but may have forgotten to clear it on the rear.

[mschor]

Ok I cleared the spooge hole, needed, but what is that bolt for on the other end of the cylinder from the brake line fitting? It goes nowhere. I decided to pull it off and put some fluid in from that end of the cylinder as well, haven't tested it out yet. Why is it there? Is this the same MC for the XJ but no line to the front?

[mschor]

Ah yes, I had switched the bolts and put the brake line where it didn't need to be. After switching back, I primed and bled the line and it feels pretty good now.

[mschor]

Black Plugs

Couple more things come up. Brakes are good for now, I started it up and rode it about 500ft yesterday. It's fowling plugs, especially #4 is really black. It also started spilling gas out the carb to the airbox. I took the carbs out, think one of the needles was stuck because it stopped leaking after I put the carbs back in. I'm wondering, would a gas-soaked air filter cause the plugs to foul quickly? Is the filter still useable, or do I have to replace it now?
Pretty sure I put K&L pilots in it too when I rebuilt the carbs, so may have to replace with Mikuni because the originals were trashed by the time I got done with them, drilling, reverse drilling,etc. I'm a little concerned about gas in the oil, but the level didn't go up, and the smell isn't distinctively gassy, more like old crud from 20 years mixed with the new oil.
I have to check adjust the mixtures and synch, but the tach isn't working so about to put a TC fuse box in and see if that helps things. Lots going on, but one at a time. Thanks for all your help so far, she's rolling

[mschor]

Looking back through my emails, I definitely got my carb kit from Partsnmore. Those are K&L brand, right? It was Part# 48-1955. Does that make sense for an 81 Special? It says on the invoice it's for 1980 XS1100.

[Radioguylogs]

Pilot Jets Might be Part of the Problem

I had a "too rich" problem caused by K&L pilots in my SF:



K&L on top, Mikuni on the bottom:



However, the pilots don't cause the gas to overflow.

Seems like you have more than one problem.

[mschor]

Yeah, I solved the overflow problem by unsticking one of the needles. My next step is to put some fuses in the new box and work on getting the tach going so I can tune the carbs. If things are still off after that I'll probably replace the pilots, and/or check the spark situation, see if it's a little weak. I never checked the vent passages between carbs when I was cleaning them, so will check that as well

[mschor]

I heard somewhere that when plugs foul like that it's hard to get them up to par again. Hoping I don't have to go through multiple plugs to solve it

[motoman]

Saw you stated you'd gotten K&L carb kits. Main issue with those kits is float needles are NOT the same height as Mikuni. K&L pilot and main jets are NOT flow mwasured the same as Genuine Mikuni jets, resulting in......they will NOT work..period. ALL internal carb components, when replaced HAVE to be Genuine Mikuni......No aftermarket junk like K&L or RD. You'll NEVER get it tuned correctly for smooth running, and will wind up wanting to pull your hair out. In other words, bike will be running to rich, and there is no fix except installing Genuine Mikuni carb parts. BTW, having the use of a pressurized sand blast plug cleaner, or as I've done, use a soda blaster. This is a small plastic hand held tank full of either commercial baking soda blaster(purchased at a local automotive paint supplier), or just plain ole' baking soda. This plug cleaning method IS the best. Definitely saves on unnecessary spark plug purchases.