DRX90 bogging on low end

[greenmachine]

The quad has no power in the bottom, just bogs down until the rpms catch up. On flat hardpack ground. If it is in soft sand or going up hill, it just sits there & bogs & wont even spin the stock tires(which I say are too big). I have seen a video of a kid doing donuts on a drx70 without slowing down, my kids 90 wont do that. I run yamalube injector oil & I have a k/n style filter with an outer foam wrap around it. Any ideas?

[Mars]

Is it new?
If not: Lift the rear wheels and run at max rpm for at least 30 sec or till the engine smooths out.
Take the outer wears off. Is the filter clean? Did the intake come off the carb.(cheap spring clamp on most 50~90cc quads)
Is the plug clean?
Yamalube is good but I think the DVX likes synhetic lube which is thinner oil.(oil pump is calibrated for a certain type of oil.)

Most kids quads have a chip on the CDI unit you can remove. (5mph to 14mph with five minutes of work.)
Check and note results........

[greenmachine]

Filter is clean, rev limiter is removed & replaced with unlimited cdi. These quads actually come in the crate with sae 30 wt oil in the injector tank according to their paperwork. (kinda makes you wonder if we are all being hosed by the "2stroke" oil companies). Intake clamp is in good shape & tight. I adjusted the air screw at 1.5 turns out. I am wondering if jetting up on the main will take care of this. Or maybe moving the clip on the needle? This started when i changed the air filter I think.

[Mars]

Try the air screw first, 1/4~1/2 turn at a time..
It could be the filter. Try putting on the old filter if you still have it.