The International Cessna 170 Association

So I managed to break my tail wheel main spring a little while back. After replacing the spring I did a test flight and a couple of local flights with no landing issues. Now all of the sudden on three-pointers on pavement the tail bounces like there's a pogo stick back there. Grass is alright. I end up shoving the yoke forward and sometimes using the brakes a little to keep it light on the tail wheel. I checked the pressure and it was a little high at 40 psi. I've tried letting it down in 5 psi increments all the way to 20 psi and it hasn't had any effect. The tail wheel has had a little shimmy since I bought the plane of the winter. Could this just be a really nasty shimmy? A tear down / rebuild is planned during the annual next month. Is there anything I can do in the meantime to get the bounces under control?

A bit higher pressure usually isn't a problem. I think what you feel is tail wheel shimmy. Assuming your main spring is holding the tail wheel at the correct angle then you need to look at the tailwheel itself. If you don't know it condition, it's worth taking it apart, cleaning and inspecting it. Count the number of flats you spin the mug off that holds the tail wheel together and replace it with the same to start. Fly and if you get shimmy remove the cotter pine and tighten the nut one or two flats till the shimmy stops.

Hold the yoke full back to avoid tailwheel bounce when landing 3-point. Moving the yoke forward as you state will exacerbate the problem.

Shimmy is a different issue and likely involves incorrect caster, as discussed elsewhere.

Full yoke back makes it worse, to the point where I'm not even attempting three pointers on pavement until I get it fixed. Camber is positive, we double checked it when we put the new spring in. My annual is out at the end of the month, so maybe this weekend I'll get an early start and disassemble the tail wheel. Judging by how the previous owner(s) handled basic maintenance, it probably hasn't been apart since it was installed on the airplane.

Don't know how you mean by "camber is positive"... but here's an illustration of correct caster:

Just a typo. I meant I have a positive caster angle, same as the bottom photo.

Well, I finally got the thing apart. I noticed when I jacked the plane up that there was tons of play when I wiggled the fork. There was also a lot of grit in the grease, the upper dust cover was missing, the bearing grease seals were shot, all of the bearings show wear, the thrust washers were worn, the fork dowel pin was worn down to nothing, and the fiber thrust washer was missing. Basically everything that can wear is worn, and some stuff that should be there isn't. At least the castings are in good shape. I'm going to order parts and get to work on the rebuild.

The only really expensive part I'm concerned about is the steering arm. The inner lip toward the rear has a burr that runs from detent to detent. I'm pretty sure I can smooth that off. What I'm not sure about is the wear to the detents. They seem pretty rounded out, but I'm having trouble finding clear pictures of a "good" one to compare with. How bad is it? Can I file new flats in, or should I just cough up the $250 for a new steering arm?

The detents don't look that bad to me. I'd reassemble it and see how it performs.
(If it goes badly for you.... I beat Bruce out of one at convention auction I'll bet you can get for a lot less than $250.)

Does anybody have any advice on how to get the bearing race out of the fork? The shape of the casting makes it so it can't be punched out from above.