My little Yamaha SR250 thumper* had been feeling under the weather recently. The rear sprockets were dangerously worn down and the rear brakes weren't working too well. I took it down to my local dealer in New Haven, Libby's. I've been shopping at Libby's since 1994 when I first came here as a grad student until I left in 2000. All the same staff were still there when I stopped by, and they all remembered me from five years ago. Fantastic service.
Somehow, Steve at the parts desk convinced me that I could do the sprocket, chain, and brake repair myself. I was feeling much more gung-ho at the store Friday afternoon than when I opened up the bag of parts and began taking my motorcycle apart on Saturday morning....
* Thumper: Single-cyclinder, four-cycle motorcycle. Named affectionately for its vibration. Also, many single-cylinders are kick-start and the strong right leg you develop from repeatedly kicking over an incalcitrant motor will earn you the nickname "thumper" among your electric-start, four-cylinder buddies. The SR250 doesn't have a kick-start so it's only half a thumper. A thump?
The SR250 Exciter is an air-cooled, 4-stroke, single-cylinder motorcycle made by Yamaha in the early 1980s. Its main claim to fame is that with a simple carb design and no complex liquid cooling system, it's pretty indestructible. I bought mine a few years ago off my neighbor in St. Paul who had it in storage for over a decade. I slapped on some new tires and battery, soaked the carburetor overnight in cleaning fluid, flushed all the orifices with compressed air, sealed the gas tank with gook, and the little thing started right up.
But three years later, my little thumper needed maintenance again. The rear sprockets were so worn that they were needle-sharp (the picture here shows the old rear sprocket on the right with what a new sprocket looks like). The chain was so glimy you needed to chisel the dirt off. And the rear brake was ... crunchy?....
Luckily, the bike has a centerstand. As far as I'm concerned, all bikes should have center-stands, otherwise you can't service them yourself easily (and certainly not by the side of the road). Yamaha also provided an excellent repair kit with the SR250. I did most of the repair job myself using only the tools in the kit. The only extras I needed were vise-grips, a handheld impact wrench (for the frozen bolts), hammer (for the impact wrench), and some blue Loctite.
Getting the bike apart was pretty easy. I had a brief scare when I thought I couldn't get the chain off since I didn't have a chain tool. But ahah, the chain had a removable link and after banging on it for a while because it was frozen, it eventually came off.
About the only major problem was that it turned out that my rear drum brake was shot. As I had thought, the lining of the shoes had delaminated and that was why it was "crunchy." But what I hadn't expected was that one of the shoes had actually cracked in half (see photo below, right). I'm glad the rear brakes hadn't decided to bind or freeze when I was on the freeway. Luckily I had gotten new shoes at Libby's and it looked like Yamaha had changed the design to beef up the thickness of the shoe plates so they wouldn't crack again. Good...... except the old springs didn't fit because the shoes were much thicker at the mount areas. I jumped in my car and went to Libby's to get new springs, but they were closed for Labor Day weekend.
In the next hour, I learned that autoparts stores are absolutely useless for miscellaneous parts. If you can't say that you need a spring for a "19xx Chevy XZYZ" then they have no ability to look anything up. So while they might have had a spring from a Volkwagen Beetle or something else that would fit in a box in the rear, the staff couldn't just eyeball the spring and do a match the old fashioned way. Since it was Saturday and I wanted to ride, I ended up bending the old springs so they would at least clamp on. It's not perfect but it'll get me until Tuesday.
Well several hours later, the bike's all put together and runs great. I'm babying the rear brakes until I can get the proper springs in. My hands were absolutely black with grease and I'll have black fingernails until next week, at least. Even the best Lava soap can't get under the fingernails. If any readers have tips (Mehyar?) for cleaning fingernails, please let me know.
All in all, I can't imagine a better way to spend a Saturday afternoon.