Is there a trick to getting the cylinder back on after installing new rings? Finding it hard to get the rings compressed on more than one cylinder at a time! A friend said to put the pistons into the cylinder first but I can't see how I'd get the gudgeons in and locked that way. Any ideas?

You are installing genuine rings 1st?? Chinese ones are not advisable and can be the wrong size.

This is how I do it- no need for a ring compressor on 400 cc bike engines.
- Oil everything up, stagger the rings as per the book, and start with the inner pistons 1st. Pinch each ring with your fingertips as you gently push the block on. Make sure you work the other piston the same as you go, the block must go on straight. . Once you have the rings in, you can wiggle the piston slightly on it's axis to finalise the install. The do the same for the outer pistons.
Make sure you turn the engine by hand to check all is ok once pistons are in.

NEVER hammer the block onto the pistons. If you feel you have to do this, it means that a ring is stuck. Pull the block back off a little. I've seen pistons snap their skirts using a hammer!

Thanks. These rings are from IMD in the UK.

Be careful with the rings. I seem to remember someone saying that they had no compression using them, probably because they were the wrong size for their piston ring grooves .
I was tempted by the price, but I ended up going OEM from the states which worked out a little dearer, but I didn't want any hassle.
Post some feedback on them, and what bike you are fitting them to.

imd rings well if your bores are worne check the gap of the ring in the bore see if it comes to the recomended gap in the book per inch on dia BET IT DOSNT.
2/ NICE LITTLE MOD MAKE IT EASY NO SPRING COMPRESSOR EH

WELL BOTTOM OF BARRELS BOTH OUTER SIDES CYLINDERS 1 AND 4 You will see a chamferd taper on the bottom of the barrels the piston dosnt get near to this
On the centerline of the outside of the cylinders file in carefully Now a radius the size of you little end pin
BUT DONT GO OVER THE CHAMFERED TAPER NO NEED TO.
pUT YOUR PISTONS IN 1 AND 4 CYLINDERS. (and take them down to the bottom so you can just see the little end pin
Put your piston on 2 and 3 conrods.
make 2 blocks of wood so that the barrels will sit on it i usualy do this in the middle between pistons 2 and 3
lower barrels on use a little radus srew driver to ease them in
when pistons 2 and 3 are in lower barrels using a smaller piece of packing wood
fit conrods and put little end pins in fronm outsides
put rag in suides of bores so when you put your circlips in if you drop one it drops on the rag.
lower your barrels down
AND DONT FORGET YOUR BASE GASKET!!!!!!SHOULD BE ON OR YOU START AGAIN lol
PERFIK............................
have a look for kawasaki z200 video i did on u tube its up ther somwhere how to do barrels.
https://www.youtube.com/watch?v=ixI3Th-K52M dont know weather it shows it or not
https://www.youtube.com/watch?v=NH6OlEoGwv4&t=76s BIT OF LIGHT VEWING FOR YOU
regards john