Some of you might have already come across my bright red 1946 Harley-Davidson WL during a tour or at an AMAL exhibition. Here’s a little winter tale explaining why an open-heart surgery became necessary for this old lady.
I bought the bike in the winter of 2021 after quite a long search: it had to be a real civilian model (WL) and not a modified, so-called “civilized” military machine (WLA or WLC). Additionally, for me, the engine and frame numbers had to match, and if possible, the original fork and tanks (yes, tanks; the left one holds the fuel, and the right one the oil) had to still be present.
Once the bike was safely in my garage, it was disassembled to ensure it would meet my aesthetic expectations. It was repainted in the original and (almost) period-correct Harley-Davidson “Flight Red” (psst, don’t tell anyone: “Race Red” from modern Ford Mustangs is exactly the same shade of red, which makes touch-ups and painting much easier). It received 16-inch wheels, a completely new wiring harness, and various other upgrades. The engine and gearbox were working properly and were left as they were, apart from a new carburetor and after a general inspection.
For about a season and a half and approximately 5,500 km, my WL ran perfectly without the slightest problem. But then, around the middle of the 2023 season, the trouble started, costing me a few of my already scarce hairs.
The bike suddenly began having severe ignition misfires while riding. There was no clear pattern to it: sometimes it ran fine, sometimes the issues started after 5 km, and sometimes only after 120 km. Occasionally, replacing the spark plug would fix the issue, but other times it wouldn’t help at all. Over the following months, I tried several new ignition coils, checked the generator, inspected the entire wiring harness, and repeatedly tested the ignition itself. But no – sometimes it worked, sometimes it didn’t. When pieces of metal that didn’t belong there showed up during an oil change earlier this year, it was clear: the engine had to come out!
When the engine was finally removed and disassembled, I wasn’t sure whether to be happy or cry. Happy because the so-called “bottom end” of the engine – the two crankcase halves, crankshaft, camshafts, pushrods, etc. – was in quite good condition. Apart from replacing a few bushings, repairing two attachment points on the casing, and addressing a few minor details, it wouldn’t require too much work or money.
The “top end,” however – the cylinders, pistons, valves, and springs – was a completely different story. The ‘ignition problem’ that had driven me crazy over the last 1,000 km turned out to be caused by a broken valve spring. Since the valve springs in the Flathead run in a tube, the broken spring couldn’t move too far off its vertical axis. As a result, it occasionally worked by chance but was often twisted out of place and stopped functioning altogether. What a nightmare! But the real shock came with the cylinders and pistons.
The Harley-Davidson 45 cui Flathead cylinders can be bored out up to nine oversizes. That means there are pistons up to the 9th oversize, with matching rings, supplied directly by the factory. So, there’s plenty of material on the cylinders, but anything beyond these oversizes is considered risky. When I compared these oversizes to the bore of my cylinders, I discovered that my cylinders were at… the 15th oversize! With the right lighting, you could probably read a newspaper through the cylinder walls.
This entire mess was crowned with two original pistons from an Indian Sport Scout, circa 1940. As if that weren’t enough, at some point, a piston pin clip on one of the pistons had come loose, leaving two nice craters in the already paper-thin cylinder walls. Conclusion: the entire top end needs to be rebuilt! Oh dear…
You should know that nearly 100,000 Flathead 45 cui models (both military and civilian) were produced, along with spare parts for about 30,000 more. Since the bike was also built for the U.S. Army during World War II, and the Americans had a habit of leaving all their equipment behind after a war, the spare parts situation in Europe is still quite good even today (it’s the only Harley where the spare parts market is better here than in the U.S.). Even 80 years later, there are still plenty of NOS (New Old Stock) parts in their original packaging, and many parts are reproduced in varying quality.
Many things are available, but not everything. And what’s missing? That’s right: cylinders!
After some searching, I finally managed to find one of the last NOS front cylinders and a reproduction cylinder for the rear (these, too, are almost impossible to find anymore). In the coming days, a large order of additional parts will arrive. Since the engine is already completely disassembled, it will be rebuilt to a top condition. This means even replacing parts that are not yet at their limit. You have to spend your money somewhere, right?
As soon as the engine rebuild progresses, you’ll be able to follow my journey on our AMAL website...
