Resurrecting an old dirt bike (part 1)

Mason's latest obsession (the bi-weekly obsessions have mellowed into bi-monthly) is getting a dirt bike. We still have the one we got for The Boy; it has been (mostly) sitting under a tarp for a couple decades. Saturday, we dragged it into the driveway and got started.

1978 Yamaha DT100E… and Mason, who blinked at the wrong moment. (The seat is also flipped up.)

I'm not sure why it was put up in the first place, but we’ll give it a good shot to get running again. Despite it being 43 years old, and thrashed pretty thoroughly before The Boy got hold of it, I think we can do it. After all, I’m even older, and have been thrashed around a lot, but I’m still going. After the initial blush of enthusiasm, Mason realized it was going to require some work to get this thing going, and started grousing about getting a new one. After a few rounds of “this is what you’ve got to work with,” he came around. A co-worker graciously offered to gift him some safety gear! (I have mixed feelings about my current employer… I have many issues, but they have taken an intelligent approach to the pandemic and my co-workers totally rawk.)

So, we got started. The gas tank was filled with rust and sludge, and the carb was a mess—white powdery stuff dried up inside, and the choke and idle adjust frozen. (I would have thought I’d have known to drain the fuel out of the dang thing.) The cables were frozen. None of the above are show-stoppers—a week’s soak in Simple Green fixes most carb problems, gas tanks can be cleaned out by pouring a handful of screws in it and shaking, and I have a cable lubing tool.

We got an impressive amount of crud out of the tank. I’m not sure it’s done just yet, but we should be down to details now. De-crud’ing a gas tank is a matter of pouring in a handful of small hardware (screws, nuts, etc.) and shaking. We started with some gas in it on Saturday, got sludge out, let it dry yesterday, then put the screws back in for more shaking. Blowing compressed air in blasts out an impressive amount of stuff, the majority of it dust but some sand-sized particles as well. Once the particles are no longer an issue, I’ll probably get some liner to seal off further rust.

The throttle was frozen to the handlebar, it turned out—once I got it off, we applied a wire wheel and file to the handlebar until the rust was no longer binding the throttle sleeve. A little cable lube sprayed down the top of the clutch and brake cables got them cooperating.

The carb is at Travis's place (he works on most of the farm stuff); when we brought some parts to fix the Kubota SUV/golf cart, I told him about the project and he offered us the use of his whizbang carb cleaner—it uses sonic waves to do in a couple hours what soaking in Simple Green does in a week. We'll have the carb back tomorrow. In the meantime, we need to get new grips, an air filter, probably new tires (maybe later). Lube and adjust the chain. There’s an off-road place in the next town up, and we at least got grips today. Mason also wants brush guards, which isn’t a bad idea, but we’ll get it running first.

While I was working on the important stuff, Mason decided to hit it with some spray paint. The back fender is now silver. The bike was originally orange, and a previous owner painted it Yamaha Blue. I’ve had to repeatedly remind Mason that, if you want to do it right, you have to take the bike pretty much entirely apart to paint it. Well, I would probably have wanted to paint it first thing when I was 11. Aging sucks, but it does bring a little perspective along with it. Meanwhile, Charlie wanted to apply wrenches to it, and Mason went off the rails (as he often does when Charlie wants to get in on the action).

If we do get it running, it will be kind of interesting to see how things pan out. He has wondered out loud if it’s too big, and has talked about wanting to do wheelies and stoppies (the latter is when you grab enough front brake to loft the back tire). The answer to that is, “maybe.” He’ll have to learn to work a manual clutch, a skill that will serve him will if he inherits the Miata. Back in The Boy’s day, I put a larger rear sprocket on it to slow down the top end (I pitched it to The Boy as “it’s easier to do wheelies”)… although I think it will hit 50MPH with a little running room as is.

I can see him tailing the Kubota, while we work on the fence, and maybe he'll ride the fence line and let us know about issues (before the cows get loose again). We can always hope he’ll use his power(sports) for good.