2024 sx300 won’t start

Try replacing the fuel filter 

Did the dealer unlock the ECU ? 

You rode it for 3 hours with it running like that?

Or was it running fine, then started acting up after 3 hours?

Fuel & oil mixture? Map 1 or 2? Air filter over oiled? Type of riding? Is cold start button popping back to “off”? As noted, replace inline filter, but being brand new, back to dealer for diagnosis…possible Ecu needs reflash or TPS setting outbif spec….

So make sure you have plenty of fuel or grab the f brake and push the forks up and down a few times. The new fuel pumps don’t pick up off the bottom but have a well that fuel splashes into. As long as your riding it’s fine but if your get low on fuel and let it idle long enough with the bike sitting it can run out of fuel. May not be your issue but I have seen that. 

If that’s not it then let your dealer look at it. Not seen many TBI bike issues. Had one bad fuel pump and that was about it. 

take it back

Normal injected 2t stuff, I would guess the dealer will have to do a throttle body re learn on it. The get super mad if you click the high idle up and turn the yellow knob on accident and it happens a lot. We do those relearns a lot!

Bring it to your dealer and have them plug it in.....

Sadly yep, I always push customers to the yz line just for ease of at home repairs.

I honestly can't imagine having to take a 2 stroke dirtbike to the dealer because it's running bad...

He never said he bought it new. 

Start with your intake, make sure there is no obstruction. Same with exhaust.

I guess before you take it in, were you shown proper start up procedure? Its pretty much the same as the tpi models and is not really covered well.

Tap the start button to wake the bike up, wait 5 seconds and do it again, the after about 10 seconds fire the bike and let it idle with zero throttle input until the radiators are warm (engine is warm) and then click high idle off and clear out. If you give it throttle before it warms up it will lock it into whatever amount of mixing and fueling it is at for the temp it is at when the throttle is used, so if you blip it and the motor is a bit rich warming up at 80f it will not lean out as it warms up and will run rich. 

Cleaning the plug isn’t going to work. You should try replacing it. They will foul plugs if you start them and let them just idle. Had the same issue.