I've done a Craftsman 54cc engine. Actually, it's from a Poulan Pro 335 chainsaw------same exact saw. I have a Craftsman 3.0 saw with 20" blade and the Poulan Pro 335------both the exact same saw.

Cut it apart with a portable bandsaw. Then finish it up with a grinder. Cut everything that's not needed to keep it together.

Get rid of the magneto. It weighs a ton and you can get an electronic ignition for it for about $150. Well worth it.

After you get it apart, you will need to cut the clutch and sprocket off the crankshaft. Remove the jug and then split the case apart. You need to remove the magneto and the clutch to split the case. The magneto is easy; just remove the bolt on the front and pry it off with a prybar or big screwdriver. The clutch is easy too. Just stick a big screwdriver in the clutch and smack it with a hammer. It spins right off.

When you have the mag and clutch removed; then you can unbolt the jug(cylinder) and split the case. Take all the bolts out and use a putty knife to break the gasket seal. Remove the crankshaft and chuck it up in a vice with a towel or soft cloth wrapped around it to keep from damageing it. NOW, you can cut the crankshaft off with a bandsaw. Don't try to cut the crank off when it's still in the case. The heat from cutting will ruin the seal on the bearing.

After you cut the crank off, you can reassemble the engine. Put the crank back in BACKWARDS. And then flip your cylinder 180 degrees to match it. The reason for this is to give yourself a bracket mount for the ignition system. One the clutch side of the case, there was an automatic oiler for the bar. Use the two bolt holes for the oiler to attatch your timing bracket. The case is the same on both sides-- except for the two bolt holes from the oiler. Flipping everything around backwards is no problem. You may have to take a Dremel to the case to help the transfer ports between the cylinder and case to match up perfectly, but it's pretty close anyway. I did not dremel my ports. Engine runs great.

Okay, so you got the shaft cut off and you've flipped everything and reassembled the engine at this point. You need an aluminum adaptor to attatch the carb and you need a phenolic(sp?) spacer to insulate the carb. My carb is a Walbro HDA------same as a G-38. So, I bought a phenolic spacer for a G-38---$12.00 Maybe you can reference your carb to another popular RC engine and buy that spacer.

You also need an electronic ignition and a timing bracket. CH or Ralph Cunningham for the ignition.

The timing bracket is just a U shaped bracket with two oblong slots in it. This will hold your Hall sensor. The slotted bolt holes make it adjustable-- for setting your timing. Bolt it to the two holes in the front of the case--where the oiler used to bolt up.

The carb adaptor will have to be tapped and threaded into the side of the cylinder. Use 4 bolts--8/32 X 3/4" Put the adaptor on as a dry fit and then drill and tap for the bolts. Take the adaptor off and then make a gasket from 1/16" thick gasket material-available at all auto parts stores--Use COPPER RTV liquid gasket maker(also available from the auto parts store) and apply it to both sides of the gasket, and to the cylinder face. Put the gasket on and the SQUEEZE!!! the adaptor back on for a very tight fit. Then run your bolts in and wait for it to dry. Don't tap the holes with the gasket in. Tap the holes with no gasket first and then when you install the gasket, it will take up enough space to make it a tight fit when installing the bolts. This keeps the carb from leaking air.

On the backplate- others have already given great suggestions about how to mount it. Run your case bolts all the way through-- front to back-- and use a nylon lock nut to bolt the backplate mount right to the case.

The magneto:
Send it to Ken Lambert. He will machine the magneto down to the size of a quarter(25c). And he will install a magnet for you. He can also make a prop hub for you. When it's done, the magneto will be about 1" in diameter and have a magnet(crank trigger) in the side for your ignition. It will have the magnet in the right spot for your timing; and it only goes on the crankshaft one way-- you can't screw it up. The prop hub will screw onto the threads over the mangeto. This locks the magneto(crank trigger) on and gives a good solid hub for the prop.

Long winded; sorry.