66cc engine bogging

[mony0_3]

I have a new engine that ran better than most out the box, after about 50 mi. it now boggs at higher rpm's and dies. I have changed the plug, carb, coil, magneto and fuel tank. It has over 140 psi. compression and the cylinder looks good. What am I missing?

 

[DieselTech]

I have a new engine that ran better than most out the box, after about 50 mi. it now boggs at higher rpm's and dies. I have changed the plug, carb, coil, magneto and fuel tank. It has over 140 psi. compression and the cylinder looks good. What am I missing?

It may be leaning out at high rpms or a lean surge will sound like bogging or bad 4stroking at high rpms.

 

[GreasyChris]

A bog is usually due to a lean condition.

 

[mony0_3]

Ok thanks, but it was the rear engine mount bolts loose. Caused the fuel to suds. They had been re-torqued that's why I over-looked them.

 

[Axl Myk]

I had that problem with one bike. The gas cap wasn't venting and created a vacuum in the tank. A small hole drilled in the middle of the gas cap fixed it.