Boxerworks.com

The bike is a '75 R90/6. I'm trying to get this bike back into good running order, but unfortunately the PO was rather ham fisted with the electrical connections. He had made all manner of "upgrades" to the bike but his SOP was to use crimp connections and not to solder and shrink wrap. There are several leads that have more than one crimped connection.

The question pertains to the correct type of solder to use on these airheads? I'm using a 63% tin/37% lead with a Weller soldering station capable of almost 900 F. Usually I set the temp from 700 to 725 F and that seems to work with most applications. Before attempting to solder I'm using a good electrical cleaner to remove any grease or oils. For some reason the OEM wiring on this bike doesn't take the solder, even to tin the ends prior to replacing the old corroded connections. I ran a search in the forum but came up empty, so any suggestions as to the correct solder will be appreciated. -Mike

I have had no problem using a rosin core solder, you don't want to use acid core.

Old copper wires are indeed sometimes a bitch to solder to.

I would recommend buying an extra bottle of liquid flux, and using that in conjunction with your solder to help promote adhesion. It is also helpful to clean those wire ends as best as possible, both with an abrasive (copper wool) and chemical (acetone), as cleanliness will also help the solder take.

I have been soldering, brazing and welding for most of my life. However, I only consider myself excellent at soldering. To expect to solder using resin core solder alone is to be disappointed. My preference is to use the paste resin out of a small can. For small wires such as we have on a BMW, I always dip the bare clean wire in the paste before attempting to heat it up. If I am going to do much soldering of stranded wire, I will heat up the can to make it a liquid. I will dip the strands into the liquid and capillary action will draw it up into the strands. If it is thick wire, say 2-0 or larger, I will heat up the wire first to get it to draw the paste up beyond the exposed wire and under the insulation. This paste gives the wire more of a seal against oxygen.

The place on a BMW where the factory goofed up is at the battery terminal crimps. Oxygen laden with moisture will migrate up under the insulation and cause corrosion. The wire will show a slight bulge and get very stiff for the first 1/2 inch or so. One must cut off the damaged portion far enough that when barred, the copper will be shiny and clean.

Also, the contractor that got the bids didn't use any NO-OX on any of the crimps. That is a failure waiting to happen. We found some would fail in the first 2-3 years.

Many know that I am getting rid of lots of BMW parts and also the majority of my life time supply of tools and supplies. I had lots of #1, 2-0 and even some 4-0 welding cable. The 2-0 has more than 1000 strands and is quite flexible. I use it to make super high quality jumper cables. The connections are all soldered onto the clamps. Or, they are soldered to a special type terminal that bolts onto the clamp. In any case the task requires so much heat that I have to use my Map gas bottle to get the heat needed.

Two weeks ago I offered my mentee a free set of jumper cables, IF she would learn to do the soldering job. She is always anxious to learn new stuff. I started her on simple wires such as found in our wiring harnesses. Then she moved on to the big stuff. We had to cut off an inch and restart a couple of times, but finally she got it. Because the losses are so low with welding cable I like to make them 16 feet long. The cost new for that much cable is well over $100, plus the jumper clamps. Now at her work the guys will see the super cables and ask where she got them. She will enjoy explaining how she made them herself, as they can't be purchased.

The tin/lead ratio just isn't very important at all. I have used as low as 50/50 and it works out just fine. The heat must just be enough to allow the solder to flow easily and quickly. I have a bottle of the liquid resin and don't like it for most uses.

There is nothing wrong with using acid for sheet metal soldering on wiring if one is very careful how it is used and knows how to clean off the tinned parts before going to resin core solder for electronics. I only go that route if I am dealing with a very dirty situation.

On my website you might wish to read http://w6rec.com/duane/bmw/solder/ and http://w6rec.com/duane/bmw/terminal/ Some of our crimps are so huge that I must use hydraulic equipment to make the crimps. The cables are so huge that we use a type of pipe bender to go around corners. We don't solder those.

In the Czech Republic I got a personal tour of the local nuclear power plant. The "wires" coming off the generators was 50 cm thick. That is about an 18" thickness wire. I was impressed. I think that I still have a photo of my mentee (same one) sitting at the control desk running the show. It was all show and the guys there just loved helping her "appear" in charge.

I was quite surprised to see that the first article by Randy Glass is linked to by more than 50 websites.

If that acid flux gets on your boxer's aluminum, you'll be sorry. It seems like an abnormally large risk to take!

One should also mention that lead free solder is about the most useless garbage out there.

I take such great care that I consider no risk with the acid. I have used water soaked towels under the work. I prefer to do it off of the bike.

Lead free? Can't remember hearing of it for soldering. I remember it for body work way back in the dark ages.

audiowize wrote:If that acid flux gets on your boxer's aluminum, you'll be sorry. It seems like an abnormally large risk to take!

It's an equally big risk to use brake fluid right over the paint on your tank, but every bike does it.

audiowize wrote:One should also mention that lead free solder is about the most useless garbage out there.

Yeah, it's a pretty reasonable argument to not be putting lead solder in our water supply (that's what it's for, Duane), but there's no reason to not have it in electrical wiring. Still, I think the writing is on the wall for lead solder and we'll end up having to deal with the lead free crap for wiring as well.

Major Softie wrote:

audiowize wrote:If that acid flux gets on your boxer's aluminum, you'll be sorry. It seems like an abnormally large risk to take!

It's an equally big risk to use brake fluid right over the paint on your tank, but every bike does it.

audiowize wrote:One should also mention that lead free solder is about the most useless garbage out there.

Yeah, it's a pretty reasonable argument to not be putting lead solder in our water supply (that's what it's for, Duane), but there's no reason to not have it in electrical wiring. Still, I think the writing is on the wall for lead solder and we'll end up having to deal with the lead free crap for wiring as well.

Yep - read this article and see how excited you get to have more lead in your life: viewtopic.php?f=18&t=7728

While we’re on the subject of soldering, I have an embarrassing question to ask. A few years ago I managed to mash the wires for the (Hall Effect) ignition sensor under the front engine cover, on my ‘88 RT. I attempted to solder the wires back together but couldn’t get the solder to stick to those wires. They appear to be nickel.
I ended up just using tiny crimp connectors to put the wires back together, and it’s worked just fine, but I’d still like to find a way to get some solder on them. Any idea’s?

It was an embarrassing moment when me and my riding buddy were leaving the restaurant and my bike wouldn’t start. Even worse was riding on the back of his Harley to go fetch my trailer. At least in the end there was no reason to blame the bike, so it still hasn’t left me walking.

Duane Ausherman wrote: Because the losses are so low with welding cable I like to make them 16 feet long.

Yeah that's not too bad a length Duane.
'Course you could always make some extension leads if needed.