I have had my 1942 flathead transmission overhauled, I fitted it back in the bike. Now having ridden the bike I cant change down gears from 3rd to 2nd while moving with out grinding the gears, I have to be virtually staionary or stopped to change down.
Changing up is no problem it nice and smooth, as the bike was a non runner when I bought it I dont know what this model should be like, any information would be helpful.
Thanks

 

Linkage out of adjustment? Bent shift forks?

 

Clutch might be pulling, check if the plates are dry and there is no grease on them.
Otherwise check if when you pull the clutch ,there is enough move to disengage the
engine from the drive.