142 engine feels like it's going slow

[Rusoap]

I'm new to building motorbicycles and had my 142hs for a few months now, ever since I got it to run it feels like it's going pretty slow. It will usually not go above 20 and at top speed it bucks slightly and the acceleration doesn't sound right. Is there anything I can do to fix this?

 

[Cozmik Mezzenger]

I'm new to building motorbicycles and had my 142hs for a few months now, ever since I got it to run it feels like it's going pretty slow. It will usually not go above 20 and at top speed it bucks slightly and the acceleration doesn't sound right. Is there anything I can do to fix this?

It could be a number of things. What have you checked?

 

[lee]

I would check the valve settings & install a NGK Iridium plug 7544 CR7HIX.

 

[CrazyDan]

Too rich on your main jet can do this.