New member with a question possibly a dumb one. I have 2 DT Yamaha’s. One is a 125 red one and one is a 175 blue one. Both were built in the late 1974. One is November and one is October. I was trying to get them started and nether of them has spark. I did clean the points and tested condenser the question is do I need a battery in the bike to work? Both bikes have keys. Not sure exactly on what I’m doing. 

Welcome from NZ.
The 125 'if it has electric start' & has "start button on the throttle" will need a 12 volt battery to liven it up even to only use the kick start.
To just kick start it only any 12volt will do no matter how small, but to use the start part of the generator a good big battery is needed.
Then again if it's got a magneto like the 175 will have then no battery is needed to get spark.
Just a warning though, without a battery on the magneto models avoid turning the lights on when running as in theory it should blow them.
Might even blow the bulbs normally operated by the battery like the neutral light if fitted.
What i'd do [if magneto ignition] is just unplug the ignition switch in the headlight then it will run all lights will be saved 'i think' [unless already shot].
Then you have no easy way to stop it unless it has a kill switch on the throttle in which case i think that could still be working on the 175 with main switch unhooked--might be wrong.
If theyre both flywheel magneto ignition then give the points a scratch if you can get at them through the flywheel slot.
Mag puller is a common 27x1LH thread pitch & is a "must" to have.
That'll kick things off for now & others will weigh in shortly.
Also 'we love pics' but the site cant take them direct so everyone 'except me' seems to use "imgur". I'm still stuck on "google photos"& just post a link.
One thing i'd forgotten is your 175 probably has lights via a switch on the left bar so just don't turn them on with no battery.
Was initially thinking the main switch 2nd click operated lights.

Greetings from Tennessee USA. 
 Are you in the USA?

Yes I’m in Wisconsin