O.K. here's the situation. I bought a high performance pro curcuit performance pipe for my stock vespa that was going 20 miles per hour. The pipe made the bike go 5 miles per hour faster. So then I put a kit on it a 64 cc polini. I didn't pick up any speed, still going max about 25 miles per hour. I thought it was the jets so I tried a 65 - way too much. There was only a 39 in there to begin with. So then I bought some 40's. The 45 worked ok but still only going 25. I tried a 49 and it seemed to big only went about 20 mph with the 49. I'm going to put the 45 back in tomorrow. Any suggestions to make this 78 vespa grande go faster? Thanks in advance please help!