hello! a friend recently purchased his first moped, a 70cc general 5 star. i’m not sure how many miles are on the kit, but he said he rode around for a few hours, and it started losing power, to the point of eventually dying. the next day, the same thing happened in a matter of about ten minutes. he would wait a few minutes, then start the bike again successfully only to have it happen again. no air leaks, no play in the crank arm, pretty crispy beige-ish plug. no oil injection on the bike. the owner prior to him had the oil/gas mixture pretty rich, so we dumped the tank, and put the proper mixture in. also, the person he bought it from had things very loose (intake & exhaust, namely), you think the air leaks there could have caused a soft seize to contribute to the piston/cylinder condition?
it seems to me like worn piston rings, so i took some photos and was hoping for some input, whether he needs new rings, a new cylinder(?) or something else i may have been overlooking, before he purchases anything. the blow back beneath the top ring makes me think i’m correct, but in my 14 years of riding, i’ve never had a kit long enough to replace the rings, so i wasn’t sure.
thanks in advance!