ok guys i been doing so many stuff with my scoot for years but now i have this problem and it's new to me i dunno what it is. it goes like this. my bike starts fine revs fine and all but lately when i ride it it make a sudden hissing sound (like an air leak, or something). this happens to me when i go for like 56kmh to 60kmh. the engine will seem to lose power. i chopped the power and parked the bike took out the spark (which burnt my fingers) checked the colour. it was a nice biscuit brown colour. i know it's not with my carb mix. i check my high tension coil and spark wire to make sure it's got no leak or making line noise, i double checked the coil's input and out put wires to make sure it not sparking to my frame. i see nothing all is clean i opened my carb just to make sure everything is fine in there. i noticed it was a bit dirty so i cleaned it out and checked my fuel hose to see if any thing was blocking the flow of gas. i put everything back together and start her up again. run and it goes fine i was able to reach 62kmhz for a mere 3seconds then it starts all up again the hissing in the engine, i take off my helmet and lower my head to check where it's coming from i can barely hear it cause my engine is still running loud. i can faintly locate it. chop the bike again and park. this time i opened my carter and checked my weights and clutch. in the process i checked my oil caps to make sure it's not those that are leaking out on me. again i find nothing. i re-callibrate the variator and hook everything back up. this time the bike took a litle while to start up but she start up fine. she idles fine and she goes fine if i don't hit 55kmh and over i'm beginning to think it's got someting to do with my barrel or barrel head. i check my pipe for leaks and the mouth for gasket wear but i still find nothing. i don't have the time to open up the barrel to check or to drop the engine and check the head since i'm still working. i hope to God it's nothing serious. anybody has a ny suggestions as to what it may be? i haven't check these areas yet but if i have enough time tonight i'll unmount her and check everything. -reed cage (blade wear or other) -generator (check for loose wire or oil cap wear) -CDI (doubt it but still a suspect) -admission pipe -barrel head -barrel -piston ring wear i dunno but i think it's got something to do with the barrel, is it possible that is ever a barrel is kinda loose or the nuts came undone that the bike will hiss like this? (i have never had this happen but i dunno it could be my first.) please help me out anyone i'm relying on you guys since all the other people around my area don't have a clue how a scooter works. thanks and i'm so very sorry for the really long post :emb:
ok i had the time to open her up last night, checked everything and i found out the problem. my lower piston ring has snapped in two perfectly equal pieces i don't how the hell that happened but it snapped. my barrel is intact no smears no scratch no microfissurations it's smooth all over. what do you guys think is best, get new piston and new rings or just replace both rings and keep old piston? it's done 1125km before this happened. while the bike is opened up i guess i'll just sand my ports clean in the meanwhile, i don't like to polish since it's no use it will bring more hesitation for the airflow. I miss my bike already
give the barrel a very light hone if you can (just to help the new rings bed in), look closely at the piston ring grooves in the piston to make sure they haven't been damaged, if there are no marks i would just re-ring it but for the price of a piston kit, it's probably not worth it.
might be a poor casting on the piston that caused thie ring to snap.. id say the lazy people at the factory didnt set the ring end gap properly tho. if its done neerly no miles you can clkaim the part from the manufactor..
ok thx for the replay guys, think i'll just toss this dome head piston and pick up a flatheaded one. flat headers are better in my book just like race bikes have flat heads.
you want to skim the head slightly to keep your compression up as a flat head wont take up quite as much volume. although i'm sure you know.
yeah all set and done m8 she's up and running again tho i forgot to take the time to break her in properly, no worries tho only squeezed once this morning but everything is normal.
