The International Cessna 170 Association

Any one out there have any experience re-attaching a rudder counter weight?

There are two common ways to attach elevator and rudder balance weights. Originally the factory used "cherry max" type self-locking rivets (CR163C-4-2 and CR163C-4-8's), also known as NAS445 types. These are the same type rivets that hold the leading edge onto the rudder, and if well done can double-duty to hold the weight.
But most repairs to rudders/elevators weights simply used a couple of #8 X 7/8" PK sheet metal screws.
Either fastener goes through the end-rib or tip-rib and into the weight. (The head of the fastener lives in the airspace between the counterweight "horn" and the stabilizer. Be careful no interference exists to control movement.)

As a matter of interest, many pilots overlook the necessity to inspect the security of those weights on each preflight. Make it a regular habit, not only to avoid a loose weight, but also to avoid a protruding fastener from interfereing with control surface movement when the fastener backs out and interferes with the stabilizers. (It'll lock up the rudder and/or elevators.)

Are there any updates or pictures of this procedure? I just finished installing lower rudder skins and a new bellcrank. I am now 10 OZ underweigh at 27 inches and will have to open the horn to install the weight. I think this might loosen the factory installed 4 lb weight. Any ideas would be grateful.

Here’s what the balance weight looks like from the inside of the rudder horn. Just FYI, since most people have never seen it.

I could be wrong, but I don't remember ever having to add that much weight to a rudder that wasn't heavily modified. Is this rudder stripped or painted? Are you certain the math is correct?

Cessnut, how many have you balanced and what do you normally find?

I have not balanced many 170 rudders, although I will be doing 2 soon. However, I have balanced many Cessna rudders ranging from 150s through 208s. Like I said, I could very well be wrong. 10 oz. at the balance weight would be approximately 8 in. lbs. That would mean it is +35. Seems like a lot.