Complex sentence structure with seperable verbs and ‘whether’

Question

Ich rufe jetzt zu fragen, ob das Motorrad fertig ist, an.

What would be a correct formulation for this sentence in order to include all elements, but still not to sound silly?

Answer 1

Let’s reduce your sentence to the underlying main clause:

Ich rufe jetzt, um zu fragen, ob das Motorrad fertig ist, an.
Ich rufe jetzt, um (etwas) zu fragen, an. (Commas superfluous)
Ich rufe jetzt (wegen etwas) an.

As you see, the last thing removed was an infinitive construction which would use um zu (rather than simple zu). These are most often placed in the Nachfeld, i.e. the bit of the sentence behind the second part of the separable verb, especially if they are longer/more complex. Thus the most simple word order would be:

Ich rufe jetzt an, um zu fragen, ob das Motorrad fertig ist.

Pulling the infinitive and its subordinate clause into the Verbklammer — i.e. between rufe and an is possible but very, very untypical. It will happen more often (but still rarely) if the infinitive construction is replaced by a subordinate clause.

Ich rufe jetzt, weil ich fragen möchte, ob das Motorrad fertig ist, an.

Sometimes, comedians use this for a hilarious effect, when they build incredibly long sentences and then have a list of particles at the end. I believe there should at least be an example by Karl Valentin, but I’m too lazy to look for it now.

Bottom line: Keep the main clause together unless absolutely necessary. Thus, say:

Ich rufe jetzt an, um zu fragen, ob das Motorrad fertig ist.

Answer 2

Sentences which talk about a intention ("do sth. in order to") use the "um zu" - infinitive pattern:

Ich rufe jetzt an, um zu fragen, ob das Motorrad fertig ist.