You need to use a real gasket. They sell them at Treats for $3. You need to also get intake gaskets, base/head/exhausts as well.
im going to be honest with you Dan. You need to do a little research before jumping into a pug motor reassembly. They can be frustrating and you need to make sure you have it all staged out before doing it. French motors require heat/freeze methods to get things together. The tolerances are very tight. I wish the bottoms ends were as easy as puch's but there not. If you got to the "moped riders association" you can download shop manuals to get torque specs, assembly steps and a breakdown of parts. there is a lot to these little motors/variators/ignitions.
Here is a QUICK breakdown of steps.
1. clean all gaskets surfaces of old gasket residue
2. press seals into carters, springs facing outwards
3. place crank in freezer over night
4. make a wooden jig that will go in a bench vise (2 pieces of wood screwed together. One on top wider than the bottom for vise gripping.) *Note. drill hole in the jig to allow for the smallest of the two bearing to fit into it.
5. heat first bearing (Smallest) with torch to Approx. 225 deg (making sure you put it on the right side of the crank)
also if you are using FAG bearings make sure you dont hit the nylon ball guides in the bearing with the torch. With these bearings, you may want to boil them in oil on the stove or something
6. quickly place frozen crank in jig with the correct side facing up.
7. with gloves, grab hot bearing and drop it on crank. Should slide down to the crank counterweight cheek.
* Note: have a piece of clean PVC pipe about a foot long on hand and a mallet just in case you need to persuade a little. Make sure the pipe is thick walled to take a mallet blow and that it is just large enough in diameter to allow the crankshaft to slide into it and allow it to contact the inner race of the bearing. It is best not to put alot of stress on the outer race.
8. Place crank and one installed bearing back into freezer
9. Heat next bearing to same temp.
10. pull crank out of freezer and put the side with the small bearing installed down into the jig.
11. grab bearing and drop on crank. Persuade if need be.
12. Place crank in freezer overnight with bearings installed.
1. Take case gasket that you purchased and put some oil on it with your fingers and sit it aside close to the vise. This oil will allow the gasket to swell a little so you get a better seal when you compress it.
2. Get your case bolts laid out properly near the vise. Number them if you need to keep their locations right.
*Bolt head should be on the variator side and nuts should be on ignition side I believe for clearance reasons.
3. Take carter half that will receive the large bearing first, place face down (inner part of motor down). Rub some 2 stroke oil on the seals to help protect them. Heat the carter half with the torch in a circular motion where the bearing sits to around 225 or maybe more.
*Note: make sure you keep the flame away from the SEALS! it will destroy them.
4. Grab crank from freezer and place it on the jig SMALL bearing down into the jig first.
5. Grab heated carter half with Leather gloved hand making sure it is still hot and slide it on top of crank in jig. Make sure the crank connecting rod is located where is should be in the carter half so it doesnt hit. Put the carter on straight in relation to the bearing! You dont want it to bind up and not go in completely. Also make sure the crank doesnt catch the seal wrong and damage it either.
6. flip your "so far" assembled bottom end in the jig over so that the next receiving crank side is facing upward.
7. DONT FORGET TO PUT YOUR CASE GASKET ON NOW. Just lay it on top of the carter half that is currently in the jig.
8. Grab the second carter half and oil the seal. Heat the carter with the torch like before.
9.Grab the heated carter half and slide it on the crank like before making sure the connecting rod is still properly located in relation to the case. Hopefully the case halves meet up. Make sure the crank doesnt grab the seal wrong!
10. grab a few of your case bolts and put them in as stated earlier. Start to tighten them down evenly around the carter so that it doesnt stress out the aluminum.This should help pull the case together to its final location while making the gasket in between seal like it should. Put in the rest of your bolts and tighten to the correct torque.
Your bottom end is now finished. whew! I need a beer stat!
There maybe easier ways to do this, ive just found this works best for me. I literally have a freezer right beside my vise in the shop:)
Good Luck! Do your research!