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Discussion in 'Airheads' started by fxray, Feb 26, 2015.
Correct, I have saved several steel gas tanks that I thought was not saveable with Metal Rescue.
While still cleaning alloy parts from the engine, I looked around here and there for a plastic grate to replace the one that is missing from the suction hood. They may be out there, but I only found one used suction hood with its grate still intact for $37. I decided to fool around and make something for it, since it doesn't show anyway. Hardware cloth was suggested, and would work fine, but I didn't have any scraps. Ace Hardware was only selling it in long rolls.
I made a little template from a scrap of plastic and trimmed it till it was a good fit in the hood opening. Then I traced that onto a scrap of thin gage steel. After I made the bit of steel look like Swiss Cheese, I cut around the edges and had this:
A little self-etching primer and some flat black paint:
And it's almost back like BMW intended:
It's a very snug fit, so it isn't likely to fall down inside and short out the starter cable. I calculated the cumulative area of all those holes as being equal to a single square hole 1.5" on a side, so probably not too restrictive. The difference is that a mouse can get through a single big hole, but not through all these smaller holes. Wasps and spiders? That's another story.
Do you use Red Rubber Grease inside your brake components?
Looking back not quite a year ago, I was rebuilding the master cylinder and front caliper on my '74 R90/6. I had ordered some Castrol Red Rubber Grease from Amazon, but couldn't decide if I wanted to use it or not.
In the end, I didn't. Now here I am with the same dilemma on the '76 R90, except I think I have worked out my preference. Some will disagree.
This topic shows up on lots of car and motorcycle forums, much like an oil or tire thread. Some people are shocked that anybody would use any foreign substance inside the brake components, let alone some kind of grease. "Use absolutely nothing but fresh brake fluid", they say. "Make sure it's DOT (another argument: insert your preferred spec here -- 3, 4, 3/4, 5, 5.1)."
I looked for Snowbum's opinion, but couldn't find where he had said anything about it. Then I saw where an inmate had quoted him back in 2012:
That was from five years ago, so I Google searched with that string and I found it on Snowbum's site, but read carefully -- he's changed his mind somewhere along the line. Here's what he says now:
"There is a product called by various names, but it is a special grease said to be for use in assembling the caliper rubber parts. Some brake kits come with a tiny tube of the stuff. I suggest you do not use it, it can cause major problems, and was NOT for installing pistons and seals anyway. Use brake fluid as a lubricant for installation. After assembly, if any brake fluid is on the outside, just use water or mild soap and water to wash it away."
Well, uh, yeah, actually it was and is supposed to be vegetable grease, compatible with brake fluid, and made for installing pistons, seals, and other hydraulic components.
O.K., so why would you use assembly grease to lube the rubber parts? Why not just use brake fluid?
Well -- brake fluid is hgroscopic, meaning it attracts and absorbs water, at least the DOT types 3, 3/4, and 4 do. Water then corrodes the piston in the caliper. I have read this, and believe it. A number of people have posted pictures of their brake piston at disassembly. They all look similar to what I found on both my airheads. Here is the latest one after I removed it; removed the old seal; then slipped the seal back around the piston. I placed the seal to show where the witness lines say it was when the piston was still inside the caliper. We can assume that this would be the normal operating position, since my brake pads showed very little wear:
Removing the seal, we see the pitting. This isn't as bad as I found on the '74, but this bike didn't sit in the barn quite as long. I used a new piston on both bikes:
Since the pitting always seems to be at the bottom of the piston (as positioned on the bike), and just outboard of the main seal, it looks to me like a tiny bit of brake fluid seeped past the seal, attracted water, and corroded the piston. Had that part been coated with grease that was compatible with brake fluid, it might not be corroded, and pistons are expensive. Really, the grease would be on the opposite side of the seal from the brake fluid anyway, and they wouldn't be mixed.
Well . . . maybe. Check out RedRubberGrease.com. I encourage you to scroll down through their pictures if you haven't seen this before. They tell you to smear it everywhere.
The instructions that come with the caliper rebuild kit also tell you to "Apply a thin coat of ATE brake cylinder paste to the cylinder bore, piston and sealing sleeve."
I decided to put a very light coat of red rubber grease on all sides of the main seal and on the piston O.D., figuring that what I put on the piston would probably get scrubbed to the outside anyway, as I pushed the piston through the seal. I did that, and assembled these parts into the caliper.
Then I lubed up the dust seal fairly heavily -- for two reasons.
This being outboard of the main seal, I figured that the grease would be on the outer periphery of the piston and maybe stop future corrosion.
The grease is supposed to make the rubber parts stay soft and flexible and last longer.
The dust seal went into place very easily. Too easily?
Reading more of the fine print in the kit instructions, they say something that flies in the face of what the RedRubberGrease.com site said about the dust seal.
The kit instructions say, "The area between the dust sleeve and the brake caliper housing must be kept dry to ensure that the dust sleeve sits correctly. Do not allow contact with ATE brake cylinder paste or brake fluid!"
Well, crap! I had just liberally coated the outside of the dust sleeve with grease before pushing it in. I read that paragraph in the kit instructions several times trying to figure out what they meant. The grease had helped the dust sleeve push in and seat correctly, so what's the problem?
Then I figured that maybe they weren't so much worried about fitting the dust sleeve, but more about keeping it seated! Yep, that's what they should have said.
Ever so gently, and with a thin wooden slat in front of the newly installed piston, I blew in a little compressed air in short bursts. As the piston moved out, the dust seal came right out of the caliper as well. The grease let it slide right out. That would be really bad news if it happened in operation on the bike. It would allow water and dirt into the caliper and up against the main piston seal. Even worse -- the dust seal could come out and lodge behind the brake pad, preventing the brake from releasing.
Here are some pictures of the old dust seal and the old piston that I recently removed:
First, here it is in normal position (note the outer part of the dust sleeve that is a light press fit into the counterbore at the top of the caliper bore):
Here's how the dust seal would be if the piston were extended way out of the caliper bore. (Even with the pad friction material completely worn away, the piston wouldn't come out this far in normal operation. This is just to show the full flex of the dust seal):
The dust sleeve flexed the other way:
I wound up removing the newly installed dust sleeve from my caliper, and then cleaning off all traces of the red rubber grease from the caliper counterbore and from the O.D. of the dust sleeve. I left the grease up inside the folds of the dust sleeve. So, this is what I think is the right way:
Now the piston will move out, expanding the dust sleeve bellows outward, but with the periphery of the sleeve staying put in the caliper counterbore. I hope this works out.
Yesterday, a friend and I made a 370 mile round trip run with the E350 to drop off his F700 down at Gateway BMW in St. Louis. That is the longest trip I've made with the van so far, and it did a great job. The Condor wheel chock is excellent also.
We found some balmy 71°F weather down there, after leaving home in fairly dense, drizzly fog for the first 50 miles or so. Gateway had the usual mundane used stuff parked outside, like this Triumph Thruxton:
I think this was a Ducati Scrambler and a Triumph Speed Triple:
An S1000 XR:
There were a whole lot more, but the outside bikes all looked about the same to my old eyes -- lots of bird beaks and lifted tail feathers. The more interesting (to me) airhead bikes, where the fenders still follow the contours of the wheels, were parked inside:
Well, mostly :
So, today I got back to a little work on the '76 R90/6. Preparatory to pulling the heads and jugs for a going-over, I took off the exhaust.
I also pulled the starter, mainly to do some cleaning. Those wire connections can look so innocent at first glance:
But, a closer look shows that the investigation was worthwhile:
The old bike is looking a little more streamlined these days as it sheds some parts.
There's still a lot of cleaning and and detailing yet to go. It'll be easier with the exhaust removed. My method this time, as opposed to a total bare-frame teardown, has been to take some stuff off; clean, polish, rework as needed; store those parts; then repeat with something else. Eventually, it'll all go back together.
So far, so good.
Damn Ray - looks like we’re in sync on our Havana Gold beauties
What a great looking bike, Dave. You have really good taste in color choice! I can't wait to see these two bikes together. Let me know when you get ready for side cover paint.
I would guess I’m 4-6 weeks out if that works for you.
Uh oh...you guys are ahead of me. I'm still working on the engine with the frame at the powder coater.
Not really going to ride until April-ish though (cold, salt, etc.).
You bet, Dave, anytime is fine. Thanks for the picture. Your wheels look really nice there. I'm guessing new SS spokes from Buchanan, and a pair of new Metzlers? Are those the rear shocks that came with the bike?
Hey, Guy, no worries. Nobody works slower than I do. One advantage of multiple bike syndrome is that it takes the pressure off the projects. A salt free ride would be really good about now, but it's just a dream. We've probably had enough rain to flush off most of the salt, but the high temp today is only forecast for 17°F. Then comes another round of snow and more salt. Gotta keep plugging along with eyes on the prize(s).
We've had very unusual weather in New England. 60F yesterday, 55F this morning, 31F now, 19F tonight, 11F tomorrow. It rained a ton yesterday to wash away the salt, so I got the V-Strom out for a quick 1/2 hour ride in the narrow window where it wasn't freezing. First ride in several weeks and likely for a while.
Hi Ray - those are buchanon’s spokes/nipples, front rim was trashed so that’s a different one from Garry, not perfect but better than the bent one. :). I sold shocks that came with bike and bought a set of Hagons - they are more capable than my bike handling skills.
Hey Ray, FWIW.... when I did my R100 around 11 years ago I bought brake caliper rebuild kits from BMW. They included o-rings, seals, bolts, and a small packet of grease. I think I used one packet for both calipers and just found the other one in my tool box. Yes mine are Brembo and yours are ATE, just more fuel for the fire.