The Big, Dumb Bike of My Dreams Is Already Teaching Me New Things
Most of my projects are easier than they seem. While the specific tasks might be complicated or specialized, I keep things reasonable by only playing with certain toys. Almost exactly one year ago, when I bought a 1988 Honda XR600R with a mutilated crankshaft, the reality of how much technology and complication I was actively avoiding came crashing down upon me.
No car, truck, or motorcycle is simple. The thousands of parts that comprise an engine or chassis in even the most basic of vehicular transportation are not the slap-dash assemblies that some would have you believe. Simplicity exists on a sliding scale, for DIYers. For the sake of argument, we’ll agree that on one end is replacing glued-on emblems and on the other is replacing the heater core or wiring harness in a modern luxury car. In between lie an infinite number of tasks and projects that can soak up infinite amounts of time and curiosity. Everyone’s happy place on the scale is different.
For a decade or so I had intentionally hung out on one side of that scale. The vast majority of my projects are vintage air-cooled models that don’t have many frills or features. Only recently have I begun moving the slider from the easy side towards the hard side, and even then I have done so in measured amounts. I completely restored a cylinder head in my garage, but it was a single-cylinder, air-cooled engine.
Rebuilding a XR600R engine might not seem like a single meaningful stroke towards the deep end of the pool. The bike is from the same era as my pair of Honda XR250Rs, which I know inside and out. The most obvious difference between an XR250R and a XR600R engine is scale: The 600R is a big lump of an engine, over 100 pounds of aluminum castings wrapped around a big steel crankshaft and connecting rod. But, as I get closer and closer to running the XR600R engine I bought disassembled, in ten different boxes, a handful of its more complicated features present hurdles that I haven’t had to stride. One such example is the dry-sump oil system.
The XR600R has some racing pedigree, but in stock configuration, it’s hardly a high-performance machine. Dry-sump oiling is typically associated with high-g cornering or acceleration, since it prevents gravity from starving the engine of oil, but using a dry-sump system can also help an engineer solve a packaging issue. The sizable engine case of an XR600R holds all the spinny bits, but that leaves no room for the oil that must circulate to lubricate those parts as they go ’round—at least, not if the engine is going to fit into the frame of this bike. The dry-sump system saves space by storing the engine oil inside the steel frame. Oil is pulled into the oil pump from a fitting at the bottom of the downtube in front of the engine and pushed up into the oil filter housing before progressing to the various shafts and bearings throughout the engine. Gravity feeds all that oil back to—wait, there is no oil pan or storage tank at the bottom of the XR600R. The oil pump is split in two: one side forces oil into and throughout the engine, and another vacuums it out of the bottom and pushes it back up into the oil tank. That second side is known as the scavenge pump.
One of the reasons I’ve had to learn about the dry-sump system of the XR600R is because the oil system must be carefully primed before you start the engine for the first time—and this one is almost ready. But before I give the long kickstarter its first real heave, I decided to spend a whole afternoon learning, understanding, and priming the system.
I’ve read about dry-sump systems and discussed them with friends for literal decades at this point, but until now everything I’ve owned and rebuilt has been equipped with a simple, wet-sump system. Is the XR600R one of the least exotic ways for me to learn the intricacies of this fun system in practice? Probably, and that’s a good thing.
Any project vehicle is a huge undertaking, from any angle you look at it. Your time, money, and sanity are on the line. You can keep any one of those three on any project, and I have only been able to keep all three by starting simple and progressing to more and more complicated projects. After rebuilding three of the even more basic wet-sump XR250R engines, the only new things to me on the 600R were the shape of a few parts and this oiling system. We curate our expertise by learning a few new things while reinforcing and evolving our previous knowledge. I’m no expert on XR engines, but on a long enough timeline … maybe.
Those pump bits look like they need some polishing. At least it’s a pretty simple gerotor pump style. Best of luck with pumping up the j̶a̶m̶ oil.
Sharp eye. That is actually a “spare” pump that I had on the bench when I realized this article kind of needed a few photos of a pump! Keeping it as a core for now, but should probably source some new rotors while I still can, just in case.
A stepping stone on the way to rebuilding a CBX 1000 that you’ll bring home in milk crates. Good luck and god speed.
Don’t you put that evil on me!
A while ago I realized that in the process of rebuilding a system on an engine that I had never done before I was slowly imagining how that system actually worked in the engine. Once I figured out how the machinery was supposed to work to do its job I could picture it running, and then problem solving got a little easier. But it’s a slow process, and getting slower as the years go by.
And in the end you’ll have a giant heavy bike that’s hard to start.
More than that, I’ll have just as much money tied up as if I just went and bought a nice used KTM 300 XC–but whats the fun in that?
I’ve restored many, many bikes and the problem with restoring enduro and dirt bikes is that when you are done, you really don’t want to ride them (at least in the dirt) because you’ll never get them pristine again. It’s a first world problem… Go ride it, YOLO.
This bike is getting built up to run the LA-Barstow- Vegas rally this year with some friends. I enjoy making it pretty, but I cannot wait to ride the heck out of it in the desert!
Reading this story got me pumped! The bike is looking pretty slick! :^)
The assembled bike looks really good!