more or less i find it difficult to engage 1st, 2nd and 3rd gears, note that the LS is one down and 3 up, initially i thouhgt that this is due to a bad linkage but this is not the case
----this is the Left Shift model with the linkage going across the back of the gearbox ?? I would be inclined to look at your clutch running clearances if, as you say the linkage is ok.
It's almost certainly a clutch issue I'd say. Try engaging a gear without the motor running and then pulling the clutch lever and using the kick starter. If there is any feeling of interference then you need more clearance. S