It's odd. It starts and idles easily, runs perfect up until about half throttle when it starts to sputter. its a very uniform sputter, not erratic at all, if that makes sense. Almost to the point to make me believe it is spark related.

It has a new plug in it and i've checked the valve clearance.

I've been through the carb multiple times in the past year since I got it. initial clean out, trash in the tank, bad gas (before I learned to put only non-ethanol in), new diaphragm.

Not sure what to look at next. Ideas?

 

there is a pin that goes through the slide it has groves in it and a c-clip that clips around the grooves there should be 5 or 6 grooves move the pin to a lower grove this allows more fuel fuel through at higher rpms to get to it just unscrew the top of the carb off remove the cable and spring and the tension clip in the top of the slide

 

may try the brake switch in left handle lever...if this switch is stuck or on the ignition system think brakes is on so it go in limp mode like an rev limiter..

 

That's exactly what it feels like,seems to cut out at a very specific rpm, runs perfect right up to a point. Back off a little and instantly recover.
I'll check the operation of the switch. It is safe to assume it can also be bypassed?

 

yes