No Power 5th Gear

[Megadan]

Originally Posted by kyriakos

Also dropped a 120 main jet in, ran carb cleaner through all jets, everything seems clear for intake. The 120 jet didn't really have an effect either.

This little detail right here catches my interest. That is a big jump in jet size. A 120 main on a Hawk with a stock exhaust system should be bogging out pretty badly, almost to the point of cutting out. That and taking the air filter off - aka open carb, also had no measurable or audible change - also odd.

The fact that there was zero change leads me to one of two conclusions, especially considering all of the testing, checking, and setup you just described.

The most likely conclusion in my mind is something is definitely wrong with the carb.

Either the bowl is barely getting any fuel to it - float level is too low or the valve is not opening fully, the Petcock isn't flowing enough due to some sort of blockage (not likely, but I won't discount it). If you have a fuel filter added to the fuel line, it may not be able to flow enough to keep up at wider throttle positions and is starving the bowl.

There is also the chance that you have a vacuum leak at the intake to head flange O-ring or Carb to intake O-ring. Or a poor seal at the throttle slide cap (also an O-ring seal).

The pictures of your spark plug (and the sound of your engine on the top end in the video) after that ride definitely back up something causing a lean condition. I would avoid pushing it hard for very long as you may cause damage to the piston and cylinder body.

If it were me, I would swap over to the Mikuni clone and call it a day. However, I would also check both O-ring seals on the intake for any sort of damage. It's not unheard of for the O-rings to be damaged during assembly at the factory.

Also make sure you don't over tighten the intake bolts to the head. Less than 20ft-lbs (about 15-18) is all they need. Too tight and the aluminum flange on the intake pipe can distort and actually cause a poor seal.