I want to travel to Germany, but fear conscription. Am I at risk?

While the other answers raise some interesting points, most of them are more of a historical or theoretical relevance. The thing that really matters in your situation is rather more simple:

Germany has abolished conscription in 2011 for all intents and purposes that might matter to you.

It's true that the constitution still has the language in there, but reinstating the actual practice would be a major political decision taking at least weeks to months, not something that could suddenly happen next Tuesday. This applies regardless of your past situation: There just isn't any infrastructure for drafting people; even the law regulating the details of conscription now states that it isn't in effect unless Germany is under attack.

I also wouldn't worry much about any kinds of fines for dodging conscription; Germany has statutes of limitations even for almost all crimes (short of murder) that would long have expired since the 70s. In case you were actually already sentenced or asked to pay any large fine back then you might want to speak to a lawyer though.

(I'm not a lawyer and none of this constitutes legal advice)

To add to Hilmar's answer:

• In the 1970s there were two Germanies, the German Democratic Republic and the Federal Republic of Germany. I'll assume that you left the FRG since leaving the communist GDR was a tad difficult. I'm not a lawyer, but I cannot imagine that anyone would try to apply or enforce GDR laws retroactively, the GDR is gone.
• You won't be drafted, period. The draft being suspended in the FRG means that it won't take a constitutional change to reintroduce it; the constitution still states that men can be drafted, but the laws and regulations to actually do that are no longer in effect.
• If you had been 17 years old when you left the FRG, you would have had to arrange for the suspension of your duty or you might have been denied the permission to emigrate. If you had come back aged twenty or so, your duty would have been reinstated. (That's a different thing from suspending the entire draft system, which is the situation today.)
• Living permanently abroad means that your duty to serve would have been suspended as above.
• Serving in a foreign army might have fulfilled your draft duty if you were drafted. If you volunteered, it might have voided your citizenship.

I'm a german citizen since birth, even though I was born abroad and only came to germany for the first time when I was 20 years old in 2012. I've stayed, studied and worked in germany since then. My country of birth has numeral citizens of german origin, so this topic has and had quite some relevance for me. So I can tell you from personal experience that you have nothing to worry about. Neither I nor any of those I know in a similar situation who came to germany after me in the subsequent years (after the 2011 abolishment of consription) were ever summoned to a military medical inspection.