Honda MC steering damper.
Good advice. I use VW one. Instant cure. Large wheels (tall) once they begin to wobble want to stay wobbling. If you ever played with a toy gryo as a kid you may remember this . Another good experiment is with a bicycle wheel. Spin it the give it a quick jerk and it will want to repeat that jerk constantly for a bit. I learned this back in the 70s with a 32 Bantam altered. Some people think that adding a damper is a crutch. I suppose it could be but when everything is right it is often still required. Just like the shock absorber tells the wheel on a bump, "Ok you got to do that once but that is enough" the damper does exactly the same for steering. My rail was Ok on very smooth tracks but even sometimes on the return road if I hit a big bump or the curbing it would do start its dance. Didn't bother me as at high speed it was perfect. When I switched to airfield racing some of the old wartime airfields are not that smooth and it would do its dance if I hit a pavement seam on a burnout. I only let the world see that once. I installed the Moog VW beetle damper the following monday . That was several years ago now. Installation on my car took about 1/2 hour complete. BTW I don't run the huge caster. Only 3.1/2degrees. And my car as anyone who has seen it run or driven it will tell you runs like it was on rails. Anyway Many production vehicles with a solid front axle have the damper installed in production. Old VW Beetles, Some Jeeps, All GM 4wd trucks etc. Try it, you will like it.
don