It sometimes is hard to get the ring in well. However, MVVS has made a provision for that. The lower section of the liner is thinner than the rest.
I proceed like this:
Locate the retaining pin, and place the ring on the piston (pull out with thumb nails, and press in with index fingers at the 10 and 2 oçlock positions at the same time. This makes the ring bend open as round as possible.
Now press the ring closed, with ring notch engaging the retaining pin. Slip the liner over the compressed ring. until the ring just clears the scavenging ports cut-outs.
turn the puston in it's final location, while still at the lowest possible position in the liner.
Now insert the liner-piston assy in the crankcase and fit the conrod over the crankpin. Go gently here.
Push down the liner as far as it will go, Heat the case, and finally push the liner all the way home. (witout rotating!!!!!)
With the piston in top dead center, and the case still hot, you can make final liner position adjstments.