BAOTIAN BT49qt-28 does not rev...

Hi Guys,

I have this 2 stroke BAOTIAN which gave me a fair share of classic problems but now I am experiencing some weird problems. Engine starts normal and idles ok, but when I twist a throttle it revs to 7k rpm and that is it. Sometimes when it is on a stand and back wheel is in air it could go up to 9k rpm but it almost immediately drops back to 7,5 to 8K. It is like something is cutting it off so it does not allow to rev to its full.
While I drive it rpms never go over 7K and when it reaches that it starts to jerk and it feels like it loses power for a second and then it kicks back in and loses again... and no matter if it is on a flat road or downhill it always get to 7K and speed is around 45 kph (30 mph). It is the same if somebody seats in the back so i guess it is not like it doesn't have power it just like it is restricted to 7k rpm. It used to pull well over 60 kph.
You can see a video of reving here and all the time throttle was at its max:



So in process of troubleshooting I have cleaned an air box, disassembled and cleaned a carb, blew all the nozzles and jets with compressed air, replaced a spark plug. Ignition coil and CDI unit were replaced this spring when it suddenly died and it did not want to start at all. Now I am out of ideas what else could it be. I guess it must be some kind of electrical or electronics issue since I covered all mechanic ones...
I would really appreciate if any of you could give me some ideas or pointers of what else to check?

 

Hi,

To close this tread let me just say that in the end the problem was electrical. As i supected the problem was in CDI unit. I don't know why but with an old CDI motor started with no problems and run completly ok up to some 6k rpm. After replacing CDI it was totally different story and motor reved up to 11K whit no problem at all. So that is it...