I'm sure this has been covered, but I cant uncover it. I would like to put the dt2 forks on a at1. My problem is what triples are used to be able to slide the fork tubes up without contacting the handle bars. Thanks

Not sure you can slide the tubes up very far before tire will hit at full compression...  Which is really, really bad.  I think most people just use the stock DT clamps.

 

Not a very good pic but i'm using DT250 forks from the first monoshock so about "78 at a guess & can slide the forks up. But as i think Mark said, got to be careful of the wheel touching the guard under fork compression if you slide them up too far. Forks are a bit heavier than AT1 forks so probably a trifle overdone. I also have forks from a "78 DT125 which i'll try on my AT1 1970 if they don't sell. Nice long travel & not heavy. Can slide them up too. 
Dt125E 1978 Frame & swingarm plus front end forks & wheel. | Trade Me Motors

Meant this pic for 250 forks 

Yes I agree, just need about a inch and a half maybe. This thing looks like a chopper. I have extended the swingarm 1 1/2 inch. Thinking I should go with 13 inch shocks. Any thoughts on this. Thanks

Use the whole front end, you will need 13 1/2 shocks.

Thank you Dave, I am using the complete forks with triple tree from a RT2, I have also installed a 21 inch front wheel. you say by using the 13 1/2 inch shocks you dont need to slide the fork tubes up the triple clamp? What shocks are folks using for this type of modification. Thanks everyone for the help. 

 
78 DT 250 forks and triple on my CT

Ok, now I see. I need the upper triple clamp that you have in order to slide the fork tubes up. I have the 72 clamps they dont have the handlebar kick back that yours has. Thank you for posting.

A friend of mine put DT forks and a 21” front end on his AT1MX. He also added, if I remember correctly, 2” to his swing arm to allow for a larger rear tire to fit.