Hello and welcome to the March/April issue. I hope spring has sprung where you are and that your bikes are out of hibernation and back on the road.
This past fall I didn’t get a lot of miles on my old bikes, but winter was particularly productive in my shop. My 1973 BMW R75/5 only saw a few hundred miles last year as I discovered a failing (original) tank lining in the spring. Using the old trick of white cleaning vinegar, patience, repeated rinsing (and more vinegar), followed by a round of Evaporust, it is no longer filling carburetors with chunks of red gunk. It took me forever to want to start on that project though. Why?
Last spring my Norton was one of the two Commando’s we used in our How-To on fixing wet-sumping issues (which later appeared in the July/August 2021 issue). It was going to spend a few weeks at our Tech Editor Keith Fellenstein’s shop, so before it went there, I removed the metal tank and filled it with Evaporust. Why? When I bought my Norton in the fall of 2016, it had been parked under a tarp on a screened-in porch and left to languish. It hadn’t been tagged since the 1990s, and the inside of the tank was downright scary. A failed Kreem liner was evident, possibly even multiple layers as several colors of ugly chunks came out when I started working on it. Though I figured I had gotten the tank pretty clean the first go-round, as the bike was revived and back on the road by the summer of 2017, there are some areas of the tank you can’t really get a good look at due to the baffle inside. Plus, I still occasionally saw little black flecks of crud in the bottom of the tank when I’d fill it.
So it sat a couple weeks with Evaporust in it, and once Keith finished the timing cover upgrade, I emptied the tank, planning to add fuel and be ready to go. But more big weird chunks of old liner came out. So the Norton tank got vinegar, time and multiple rounds of flushing with hot water until nothing nasty was coming out anymore. I followed that with a round of clean Evaporust and fuel, and we were ready to go. So, yes. I waited to start on the BMW tank because all my cleaning vinegar was in the Norton tank and I was too cheap to go buy more vinegar and more corks to plug up all the holes.
There’s an old saying that there is no such thing as owning too many motorcycles, but there is such a thing as having too many carburetors and too many batteries to keep up with. I’ll add dirty fuel tanks to that list, thank you very much.
Both tanks are clean now. The BMW has fresh oil in all the right spots, it has a new battery, the valve adjustment has been checked, and it’s ready for spring riding.
Using vinegar to clean tanks works pretty well, if you have patience, but I did learn one lesson in this process. Vinegar will eat the rust in a fuel tank, but it will also eat the pot metal used in the rivets that often hold the spring and seal to the inside of a fuel cap. The Norton tank cap got upgraded with a new seal, spring and a screw in place of the rivet as the old one fell apart when the vinegar ate the rivet. If you’re cleaning a tank with vinegar, open the fuel cap wide and use a large cork from the hardware store to keep the bung stopped up rather than using the cap. Unless you just like drilling and rebuilding fuel caps. Take your pick.