[Pajamaboi]

First off here is video of issue.

So I bought a 2001 300 2x4 and have been loosing my mind over this issue for 2 weeks now.
Compression tested and had 139 psi. Replaced fuel filter and fuel line. Cleaned and rebuilt carb twice looking at everything to make sure it looked good. Has stock sized OEM jets. Replaced coil and spark plug. Borrowed a good working carb off my cousin’s 300 4x4 and it mimicked the exact problem. So I feel I can rule out carb.
Adjusted pilot screw from almost all the way in to 4 turns out with minimal change.
Airbox boot to carb has no pinholes or cracks that I could see.
The only time it runs better is if I block most of the air filter hole going to the carb. Which is what made me think it was a leak in that boot. Yet after fully looking it over, taping the ends, tightening clamps more, and spraying brake cleaner around everything while it idles to see if it revved up. NOTHING changed. Also btw it idles great. It’s just once you try and give it throttle you will get misfiring and it try’s and die.
I even swapped old coil back in and it has same issues. Besides tracing the wires going to the coil back. Idk what to do.

 

[NMKAWIERIDER]

At first because it was OK for the first 1/4 throttle I though split CV diaphram but doing the same with another carb points somewhere else...like low ignition power from a bad or weak battery or charging system or a failing pulse coil. Test those. Might also check the flywheel key.

 

[Pajamaboi]

So I tested battery and it all checks out great. Charging system works too. Even swapped in another battery since I’m desperate and nothing changed.
Could a failing cdi cause weak spark or would it just go out completely.

 

[NMKAWIERIDER]

So I tested battery and it all checks out great. Charging system works too. Even swapped in another battery since I’m desperate and nothing changed.
Could a failing cdi cause weak spark or would it just go out completely.

CDIs are pretty robust and don't often fail but when they do, its usually 100% dead in the water. Strongly suggest testing the pulse coil and see if the flywheel has slipped.

 

[Pajamaboi]

I currently don’t have time to take off side case and check, but will definitely update with what I find if I ever fix this issue. My arctic cat 500 just started having the exact same problem so I need to step away for a bit because I’m a month and $2600 into 2 four wheelers and they still won’t work.
One more thing I thought of…could there be air leaking around the plastic threads on choke cable. Would that cause this issue possibly??