Pull the rubber boot from the air box to the carb off
put something in the carb to lift the slide
shine a light in the carb open the throttle and see if the butterfly is opening all the way
remove the top of the carb take out the diaphragm and check for any tears or holes
if the diaphragm is torn or has a hole in it the slide wont lift up the needle to give it fuel from the main jet

 

Made $800 so yes, I fix up lawnmowers very often too but obviously a motorcycle is more intense, so its not always a carb problem like 99% of mowers. Thats why Im pretty confused about the loss of so much horsepower when it runs, starts, and sounds perfectly fine but just doesnt have the power it should.

 

If this was the problem, would I not be able to turn the throttle all the way? Because I can give it full throttle, but it doesn't actually give me power passed 1/2 way?

Regardless, I will do this anyway.

 

Pull the carb boot.
Manually lift the slide and see if the throttle is pulling the needle up all the way, full range. (ck butterfly if there is one).
Put the camera somewhere where it can see the slide, this may be tough. and ride it full throttle, the slide should go up all the way, if not, maybe diaphram issues.
If you can't get a camera in there, start it and crank up/down on the throttle and see if the slide lifts.
Another option is the main jet is clogged, take it out and clean it.
I would say it is the diaphram, cable pull, main clogged in that order.

 

The diaphragm can be tricky to get back in.

 

What the????
It doesn't sound right...
That was WOT?
Change the plug, check the air filter, check all the easy crap first.
Then go from there.

 

I will change the plug tomorrow, but the air filer isn't the issue.

Im just going to take apart and put back together the carb myself tomorrow so that I know it was done correctly. After some outside research and from this forum I am more and more convinced (and hoping) the diaphragm was installed incorrectly the first time.

 

There's either a mouse nest in the air box or a jet is clogged. Winter in the NE and critters look for cozy quarters...I've removed nests or the start of one from many bikes.

Alright, never mind about the filter. You beat me to the punch.

 

Just checked the airbox/tube 5 minutes ago. There isn't anything I promise. Did you watch the video I posted? It may help a diagnosis. There are no problems starting it and it never dies when idling. So I'm thinking its the diaphragm.

SOMETHING I FORGOT TO MENTION

The idle stays steady for a little while and then when I accelerate in neutral, it idles about 1000rpms higher than usual, but the throttle doesn't stick when decelerating when I am moving.

Its seeming even more like the diaphragm now...

 

An incorrectly setup MCM mod?? Sorry just floating ideas. Oil at proper level?? Coolant not frozen?? Brakes not sticking? I wouldn't be able to sleep if this was my bike, I'll probably wake up tonight thinking about this....errrr