Welcome to spring in Illinois.
Yesterday I got the bike out and cleaned it with a toothbrush and Ajax, and it looks splendid again. It's not perfect but it's better, and I think when I have another day off I can spend a little more time on the details.
Speaking of details--
Today, the new set of piston rings arrived. I have double-checked them against the piston type and found that the part numbers match.
...and one of them does not fit, exactly as is the case with the other set I have.
*sigh*
Since I have two sets of rings, of which one ring per set fits the piston, I can now reassemble the dirt bike and have two piston rings left over which do not fit. But you know what this means, don't you? It means that the piston I have is not in fact a 12110-25100-050 piston, but some other type...and I despair of finding out what other type that is since there are absolutely no distinguishing marks on it.
Inside the piston it says "Made in Japan" with the Suzuki logo; there are also casting marks--"8 T" in staggered formation, "ART" together, and some kind of marking that might be "IKI" or "IK" or nothing at all. There is no way I can relate these to a part number, though I suppose if I were to go to Japan and scour the old folks' homes I would eventually find someone who knew someone in 1970 who worked in the right foundry and who could probably have told me what those casting marks meant...before the Alzheimer's, I mean.
Argh etc.
On the plus side, it's an air-cooled two-cycle engine, and tolerances for those are notoriously loose because the operating temperature can vary so widely. This is a bike which had only one piston ring for most of its operational lifetime, on which the original piston was scored probably beyond rehabilitation, and which kept running beautifully despite all that. I think having slightly incorrect piston rings will not cause undue distress.
Now I know why restoring old vehicles is so expensive.
* * *
In other news, today the Jeep had the Death Shimmy bad.
Driving home from work, I was accelerating through a green light when the steering wheel started going jig-jig-jig-jig-JIG-JIG-JIG-JIG-JIG-JIG-JIG-JIG--
It was a resonant vibration at about 2 Hz, and because it was happening at the natural resonant frequency of the steering system it was not getting any better. Normally there's a bit of a shudder around 50 MPH that goes away, but this time it simply would not stop, and in fact showed signs of getting worse; if I hadn't stopped it probably would have continued until the front end tore itself apart. Instead, I pulled off the road, and the wobble stopped when I slowed down below 40 MPH. That would have been fine if it hadn't done exactly the same thing about five minutes later on a different road.
I can slap a "band aid" on it by getting a new steering damper on the thing. That'll cost me a few shekels from Advance Auto or wherever, but I know the damper is shot (last time I was under the truck, it was clearly leaking) and it ought to keep the shimmy from getting out of hand. But it's not a fix and I'll need to get that sorted, one way or another.
The best information I have says these are the possible culprits:
Wheel bearings...basically the entire front end, in other words. I've checked the tie rods and ball joints for play and not found anything significant--nothing that was obvious--but when I have it up on jack stands again I'll re-check the damned things to see if anything's changed in the past few weeks.
Steering box
Tie rod ends
Ball joints
Tires
Man, what a pisser. Well, that's how it goes, I guess.