Ive got a yamaha neos 100,its had a new barrell/piston rebuild but did not know how many miles it had done since,ive ridden it and twice at 40 it cut out,it started again and now ride it at 30 but its very smokey now,is this a mixture problem or is it the rings,if it is rings is this a costly job

SOURCE: Engine cutting out when open throttle. YAMAHA NEOS 50cc MOPED

i had a simuler problem with my honda cr 250 moto-x bike it would start fine and you could keep it ticking over with the throttle(i have deliberatly unscrewed the tickover in case i come off,it will cut out) when i got on it,it would go for about 400-500 metres then splutter and die and not start again for around 5 mins. i immediatly knew it was a fueling problem. so after stripping the carb and giving it a good clean out i was baffled when i got back on and it still done the same. i then dismantled the fuel tap cleaned it all out and put it back together and tested it,it was very very slow so i unsrewed my fuel cap a little and was greated with the familur gush it should deliver. problem solved! the vent in my fuel cap had crystalised up,so the fuel was coming out but the air was not getting in,causing a vacuum and slowing down the flow and basically emptying the carb quicker than it can fill back up!!! clean your carb,fuel tap and any vents in your cap or tank. if this does not work then your bike must be over fueling or low on compression.

SOURCE: my tzr125 2rk 1991 the bike splutters in every gear

gett a high preformance spark plug as i had the same problem with my bike