I am fixing my friends 1977 dt that he got for 100 $ i found a paper in it that had an old identification paper that said its a 175 but he told me it was a 250 anyhow i put a new battery new spark plug new gas did a carb inspection and it looks like it has a after market carb and filter the carb looks fine so i kicked and kicked and nothing he told me it started before once with him but turned off when he put it in first gear so thats why i did another carb inspection and by that i mean i took it apart but it all looks fine one night i checked his spark and it work so i tried starting it again nothing somehow i decided to do another test and well i got nothing now no spark what do you guys think i was thinking coil and maybe checking the points but im not sure yet also is there anyway i can check if the kill switch is working properly i tried kicking once on what i think was kill switch on and the kick starter shot back up.

First thing is to check the VIN against the VIN tables in the Tech Library here and identify exactly what you are working on.

Aftermarket carbs can be problematic in terms of getting it to run but of course won't affect spark.

Pictures are always helpful too.

here are some pictures sorry for the bad quality. also thank you =)

OK . First off , did you paint the frame and kill the grounding ???

I like to do that.

Welcome if you're new.
I think you said you kicked it & the kickstart came back up. From that i'm guessing you mean it kicked back on the kick start. So that sounds like it's broken the crank key that locates the flywheel in the magneto which makes it spark at the right time. If you check for spark with the plug out & resting on the motor & it "does" spark, then i'm still thinking crank key, as 'will' spark but not in the right place for the piston. Need a proper flywheel puller unless its now loose enough to easily come off. Pullers are cheap & everywhere on ebay. 27mm left hand thread & fits a lot of bikes not just yamaha. Broken crank half moon key you'll need to tap the broken piece out with the screw drive as it'll curl up out of the keyway & is a half circle shape--well a fraction of a circle. Tap down on one end & other end will pop up. Also there will be a small straight piece of it in the flywheel slot to tap straight out. When its back on with a new key, be sure to tighten it good & tight, solidly tight, not in gear with the brake on tight. They love to eat flywheel keys for breakfast.
After all that, & if that's 'not' the problem, i'm sorry you had to go through reading it all lol. Cheers. ps, DT250's are all good models, if it is a 250. Also it doesn't need a battery to run or spark although without one you just might blow light bulbs depending on if it has a regulator fitted which i think they would have by that year model & the regulator saves the bulbs if the battery is missing or disconnected or out of water.

no its not mine me nor my friend painted anything

thanks for the help =)

do you know what the point gap is on the dt 250 1977? the vin is 1m1 006196

Points gap is always close to 15 thou max. Gap does alter your timing a little but it'll be close enough for what your trying to achieve--which is get it going. just thinking, your model the base plate is adjustable but if its not been played with the marks left by the screws will be close to halfway on the slots, maybe slightly past halfway by memory.