I have an 87 sportster When I got the bike it came partly disassembled ... Headlight has 3 short wires that come out 2whites and a yellow where do they tie in?

 

Sounds like an after market light. Look inside the bucket, is there a black the goes to the inside of the bucket from the bulb socket?
If so it's self grounding and the whites are to the high and low beams. You'll have to figure out which one go where. The yellow is for driving lights. and is usually connected to the low beam.

 

Dupe. How do you delete these days?

 

The headlight has 3 connections. One is a black to ground. The middle is a yellow and the two white wires go to the last. I think the white is high beam and the yellow is low beam, but the yellow goes to the middle. The 2nd white wire goes to the high beam indicator, so that'w why there's 2 wires.

A factory shop manual will help you out tremendously.

 

I have a service manual but the wiring seems to have been changed. I had to buy switches and switch housing the previous owner had it pretty much down to the basics ,no signals and three toggle switches to turn on and start in the dash. I can see that 2 of the wires connect to the switches now going by the book it shows a yellow for low beam and white for high beam and the other white looks like its supposed to go into a 12 point plug but I don't have any of those so what does it go into ?

 

Use your tester and be sure you have the signals etc. hooked up if there is nothing left consider it a spare. Be sure to sketch out what you find and do and put it in the back of your manual it might help later.
If the wiring is that messed up you might want to look at getting a kit like the ones from One Wire. I have used these on a couple bikes and it really cleans things up plus with some systems you can run LEDs and run, brake, turn combos.
Cheers

 

If Dr. Hess is correct it would go to the high beam indicator in the console.