Hi there, so i am at a dead end because I don't know enough yet. So not sure if it will make a difference but Ill start from where I think it started. I bought my engine kit and installed it on november. ran great., had some hiccups hear and there , mainly clutch adjustment issues. Runs great been up to about 45-50 down hill on an 80cc seeutek motor. Im sure this ia a cheap motor but not my issue. Went about 30-35 on flat. I'm saying this motor really surprised me and love it. Have about 600-700 miles on it since installed. Ans this is what I did when bike started to have problem. Ive been wanting a new gas line as th done I had was little too short and eventually started leaking and popping while riding. picked up a new line from auto parts store not giving much thought that the new one is maybe 1/3-1/2 bigger ID than original. Also I put new carb on it from another motor I had that never amounted to much. Same speed carb only difference is the fuel line now connect in the vertical position and not horizontal. don't know if that matters. don't think it does. had a little issue with getting the first gas to flow through the lines from being vapor locked, according to a buddy, so i got the carb filled and lines filled and reconnected. Perfect , great, grand. went on a couple short rides no issue. Then the other night I started on a longer ride which i made it to about 5 miles before all the sudden at the bottom of a hill I was going full throttle down hitting the harmonica perfection of the motor and probably going bout 45. I porobablyt should add I do tend to ride my bike fast and hard. and if My motor blew up at least I could be certain that is the reason. But at the bottom of this hill the motor started sputtering and almost seemed like it was not getting gas. but i pushed on for another 5 miles to my destination. gas couldn't be issue cause I had plenty and you can see it through the gas line. So i took spark plug out and cleaned, my and my uncles thinking that that was the issue and we didn't have the tools to do much else. started on my ride home and about half way home started to do it again but i made it home. Let it sit for a day and also got a new spare plug. B6HS NGK. filled with gas warmed it up like I always do and went on my way. was running fine until about the same distance when it bogged way down when on throttle and eventually died and would start again. would attempt to but just couldn't get it to fire up. got it home. thought maybe it was the head or head gasket or cylinder had a crack. changed all of them from the other unused motor I have. started it up got it warmed up and went on my way. about half mile into my ride it did it again. no power on throttle and then dies with not being able to get going again. peddle peddle peddle sounds like it wants to start but just wont. sorry this is such a long post but just wanted to give all the facts. Does anyone have any thoughts and hopefully answers to get this thing going again. I am very unhappy when don't have my bike to ride.