Okay, I understand, I'll investigate
For now: Motorbikes seem to have only few insignia, the bikes of your or similar color are most likely related to the "Afrikakorps" (yes...as it would be in english)
The proper insignia for that would be a palm tree (uhm..loose the swastika as germans do on restoration)
(this link contains the "original" icon WITH Swastika... Sorry about that that's why it's not clickable!)
https://commons.wikimedia.org/wiki/File:DAK.svg (DAK -> Deutsches Afrika Korps)
Some impressions of military motorbikes from that era:
This one obviously has a lot of markings.
All technical: Achsabstand (wheelbase in cm) Tire pressure (in atü *) and Achsdruck (Axis max load in kg)
And some Luftwaffe company (which does NOT correspond to the WH license plate meaning
Wehrmacht
Heer so
army not airforce...*shrugs*) emblem I have yet to decipher.
The black icon on the fender is nothing but the icon of the manufacturer Zündapp
This one is rather hard.. no markings but the company insignia;
you can tell it's Afrikakorps by the palm tree and that its some sort of artillery because of the the lines (two short bold lines with a long thinner line in the middle) but the rest... I have no idea. (not even what the goggles above should indicate)
Again tire pressure on the fenders and the palm tree this time with the spear circle
That's from the Flakeinheit (FLAK =
Flieger
Abwehr
Kanone - Anti Aircraft gun loosely translated.. oh einheit means unit

)
the "crossed circle with a hammer" thingy on the back means "Kraftradschützen" (motorbike marksmen ..sounds odd *shrugs*)
And another one
Yes that looks cool, but as a rule of thumb:
Better not use runic symbols 
That is a
Wolfsangel
And for a rough understanding a set of very basic symbols:
I'll get back a soon as I know more
'sid
*atü =
Technical atmosphere above (
über) datum