bojas

hi guys I`am owning the mt03 and I`am a bit concern about it work, being more specific the engine is going up and down on tachometer on neutral I`am not sure that is normal because of the one cylinder or is not regulated properly. the same thing is wen I`am riding with small speeds between 0-30 mil/h if I`am trying to ride with the same speed without acceleration the bike twitch a little bit. i don't know that all this is normal for one cylinder engines or is sth to do with engine need to mechanic attention so sort out "unstable" work.