What do you do when you pick up a Harley-Davidson WLA that hasn’t run in years because it’s one of your dream bikes, ride it hundreds of miles home, and then figure out it may be even cooler than you thought it was? If you’re smart, you’d probably hit up Matt Walksler from the Wheels Through Time Museum for help. Thankfully, that’s what the SRK Cycles guys did—and that’s how they found out their WLA was a wolf in sheep’s clothing—with a high-po, vanishingly rare WLDR racing mill at its heart.  

Now, after taking their new bike apart and bringing it on a 10-plus hour drive to WTT, the SRK guys also made the crucial choice to leave their engine with Matt for a full rebuild. So, in this video, Matt takes us through what he’s seeing as he dives deeper into this particular engine—and of course, it is fascinating. 

WLDR engines, as Matt explains, were only made for five years—from 1937 to 1941. The cylinder heads were decked to increase compression, the stock engine cases have matching numbers and therefore came as a set from the factory—there's a lot of cool stuff to see here. If you’ve been watching the SRK series, you’ve seen some of these parts before—but not in this shape, since Matt apparently took the engine cases over to the ultrasonic cleaner, then bead-blasted them to get them all shiny. Under all the grime of 40+ years of sitting in a shed somewhere, it turns out those motor mounts are totally perfect. 

After getting that far, Matt explains that while those engine cases match each other, they’re from 1943 and probably weren’t original to this engine. It makes sense—guys were out racing bikes, blowing engines, and replacing the parts that needed it as they had to. As further evidence, the pistons were 50mm over standard, so this engine had clearly been rebuilt multiple times before it sat for so long, waiting for the SRK guys to buy it.  

The good news is, while it’s not possible to tell exactly which internal parts are original to this engine, everything inside is all genuine OEM parts. As Matt repeatedly says in the process of going over this engine with a fine-toothed comb, whoever worked on it before clearly knew what they were doing, and took care in doing it. That’s really all anyone can hope for when diving into any type of pre-owned bike, let alone something as special as this.  

Remember those super-rare WLDR cylinders up at the top of this engine? Closer inspection revealed that both of them unfortunately had very small cracks up toward the head bolt. Because they’re so rare and unobtainium, as Matt puts it, it’s worth doing everything you can to try to save them—so he had an expert welder buddy of his work his fiery magic to make them good again. They then redecked the surface to make it nice and smooth for the gasket to mate up with once it’s time to put it back together. 

There’s also a slightly bigger intake valve to help this engine breathe, which is interesting but not entirely surprising. There are also progressive-wound valve springs, which was definitely a racing upgrade. Remember those hot cams Matt discovered in the initial teardown of this engine? Here, we get a closer look at both a cam from this WLDR and a stock cam from a regular WLA—and the difference is readily and visually apparent, no micrometer necessary.  

After a little more engine talk—this WLDR has a lightened flywheel, it turns out—Matt escorts the camera upstairs to start up a 1939 Harley-Davidson WLDR that hasn’t probably run in 10 years. Does it start right up after Matt goes through the full starting procedure, handily giving us a history lesson all the while? I think you know the answer. Just make sure you have your headphones, because you’re going to want to revel in its glory. 

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