I took the instruments off my '78 /7 somewhere in the process of swapping forks, and when I took a close look, I found that most of the scew holes have split/cracked. I may be able to replace some of the parts, but is there a way to fix this? If I knew what kind of plastic it was, I could probably find a glue. Have any of you found a way to repair plastic like this?
The ones on the outside you can add a little glue and the one for the instrument plug I have the same problem so I will try to machine a threaded aluminum piece that we take the place of the broken part and screw in from the backside of the light board. PM if you want me to make two?
I've found the super glue at hobby shops really works! It's the best place to get your super glue anyway, but they have several different variations that work better in different applications. There's one that works especially well on plastics and so far I haven't found any it doesn't work on. Get the accelerator too - it causes the glue to set instantly. I haven't tried it yet on the gauges, but don't see why it wouldn't work. Also, that black plastic is ABS, so if you can find the real ABS cement (not at Home Depot or Lowes) it'll work for you there. I've tried the stuff at Lowes and it's slated as working for all sorts of different plastics including ABS, but it doesn't. I think I got the good stuff at either True Value or Ace Hardware.
Well, after a little fiasco trying to buy a new speedometer (I bought what I was told was 'the last one in the country' and it arrived damaged) I decided to take a crack at repairing the gauge I have. I was able to find a housing in better shape from a wrecker, and some of the smaller plastic pieces I got from Max BMW. As for the gauges themselves, I went to a local hobby store and bought thinwall brass tubing in a few sizes. I cut some little reinforcing rings to hold together the posts on the gauges that are split: It's an old bike, it should have old gauges, anyway. This should keep it together enough for now. While I had the gauges apart, I found this interesting little artifact: Someone was obviously in there before me.
I like that a lot. Looks like a very good idea for pre-emptive strengthening even good threads. It takes experience/skill to learn the proper feel for tightening those plasitc threads, no less so than for the alloy threads. Those collars would be helpful in reducing cracking damage. A trick to keep in mind with those threads. When replacing the screw, turn CCW until you feel the screw drop into the housing thread before you begin to tighten. Helps prevent cross threading which tears them up instantly.
a while back. Dogdammit, I'll try again, By the way, I LOVE the brass tubing fix thingie, Totally AWESOME! I just looked, I only have one left and it's rusted to shit. The part is only $1.89 from BMW, here's the part number 62111243111
I will see if the local dealer has one in stock, or wait until I am ordering other parts and include that. Thanks for trying to get one into my hands. Dana
Are they getting more rare suddenly. A year or two back they were a regular ebay item. What does a decent working one go for these days?
Not sure what the story is- I only know that the dealer I ordered it from said if I wanted to exchange it, the next one would be coming from Germany. I didn't really look at used gauges to get a sense of what they were going for.
Those screws always crack. they crack from fatigue and age. It's just a lousy design. no more no less.
I used to think they were over-tightened and that's why they cracked. That may be, but anymore I think it's just that they've corroded a bit and seized in there. Then when you go to loosen them, they pop the plastic. I anti seize the screws when I put them back to keep it from happening the next time. And they don't need to be torqued very much - they do have the outside cover over the top of them, but I've never seen one loose. I used to think it was a poor design, but revised that idea. Now days they wouldn't use the brass inserts, just screws into plastic. So things have definitely gotten cheaper! And they have lasted 35 or more years at this point - a lot better than I'd first expected. But they have gotten stupid expensive to replace new! And finding a perfect, undamaged used one is more difficult all the time. But I do like the way the instruments are sealed up without having a crimped-on bezel to remove. A few screws and it's out. But that light board! Whoever came up with that one should be shot! What a pain in the ass those things are!
Those type boards and what-you-call-em circuit strips I first saw inside the Hewlett-Packard hand held calculators in the early 70's. But it was all soldered except for a pin array similar to the instrument connector on the back. My HP-45 is still function nominal at 40 years. The case is the same, screw threads in plastic. My $400 Fluke 88 is the same, plastic threads for metal screws. Wouldn't it be nice if someone would forge them out of alloy so we could have more threads to strip anyway. I have seen plenty of brass thread inserts pulled out as well. For sure, when replacing those metal screws into plastic threads first turn them CCW until you feel the screw drop into alinement with the thread. You only get one chance to cross thread those. In fact, when new, they have no threads. The screws are designed to be self threading in first application/assembly at the factory. In every case they need to be just barely firm and not a bit more.
This last statemennt is my take. I have been inside these housings many times and have never stripped or cracked the threads. Methinks ham fisted tactics are at work here. Just a little snug with careful attention to avoid cross threading is all that is required.
