Samurai BJ 1992 engine is not running around

Hello in the round, we have a Samurai Bj 1992 with 145000km. At times the engine does not run perfectly, as if it would only run on 3 cylinders. Before I let the Greeks over my sanctuary over it (it is used on an island in Greece) I wanted to go into the round questions what that can be, it is already clear to me that it is difficult from a distance, but it is worth a try 🙂 The first time I noticed it in the “winter”, he went the first 500 meters as if it were only 3 cylinders in operation. At that time I thought it was because it is cold. About 2 months ago the problem was on the 20 km and was gone at once. After that I gave new candles, cleaned the distributor cap and the distributor finger. After that it was actually quiet, until after a month the same happened again, but only a few minutes. When it is cold, it starts great, hardly I had turned the key, brum, purrs already. Hardly it is a bit warmer, it takes about 2-3 seconds. n before the engine starts and it doesn’t run as nicely round as when it is cold. 1.) I noticed a rubber part in the carburetor, whatever that is, is damaged, can this be related to it, or what function does this part have. See photo “Gummi2” 2.) Should or must one renew the distributor finger/cap after 140 000 km? Suppose he doesn’t have any interrupters, that I also have to change them, right? Thanks already for the help