ROFL dude!
I litterally JUST put my 84 250r together and had the SAME problem!!!!
I think all it was was the clutch plates stuck together!
I took it apart and it all seemed fine but the plates were stuck to the fiber discs.
Heres how I fixed it.
1. Adjust clutch cable at the clutch arm all the way tight.
2. Adjust cable at the clutch perch 50% out.
3. Put a 100 mm socket and ratchet on one of the many nuts on the clutch pack and turn it clockwie with the lever pulled. Then try to turn it without holding the lever in. Adjust it at the PERCH until it seems like it works good with you turning the pack with the ratchet and socket.
4. Put the cover in, put NEW oil in it.
5. Start the bike and rev it up real good and pull the lever in and out a few times. Then pull it in and let it slam out a few times.
6. Try starting and going into gear
7. If it still stalls adjust the clutch perch out alot more until it works to put it in gear but then it prolly wont move - clutch slipping.
If you get it to slip and not go forward in 1st rev it up good to get those plates moving around and unstuck.
Thats EXACTLY what I did to get it to work and now its PERFECT!
Roger
1984 Honda ATC 250r
Bored .020 over Wiseco, Answer silencer, fresh motor, New connecting rod and balanced crank, Boyesen 2 stage power reeds