Help with Stalling / Flame-out

I have recently moved to an '09 YZ450F and installed a Rekluse Core EXP 2.0 and set the bike up for hare scrambles. I've had the bike for about 2 months and really like the bike. Up until this weekend I've had no issues with stalling and the Rekluse has been working great.

Now for the question, I raced a hare scramble in north Texas this weekend, the conditions were elevation approximately 900', temp was 100F (crazy I know), dry and dusty. The bike flamed out / stalled multiple times at low speeds, usually when making a quick transition from blipping the throttle to slamming on the rear brake. I'm thinking this is a jetting issue and not a Rekluse issue. The motor and exhaust are completely stock; my current jetting is 45 pilot, stock needle on the 3rd clip, 160 main, and fuel screw 3 turns out. Is this a problem that can be fixed by turning the fuel screw in (and maybe the idle up), or should I try a 42 pilot for the extreme heat?

One final question; any recommendations for jetting in Colorado (Taylor Park) in July?

The 45 at 3 out is a bit much for the conditions, most likely. Stalling on a sudden throttle drop from a loaded condition is almost always the result of running rich. Running the idle as lean as practicable will prevent this. At 3 turns out, you could just try turning in until you get the right response.

If the bike runs well at 1000', rule of thumb would have you reduce the jet sizes by 5% for 6000'. I'd guess a 42/155 or 42/160.

I went riding this weekend at Red River MT in Bulcher, TX and had the same issue. I was running the pilot screw at about 2 out. I've got a flywheel weight on order and I'm going to play with my Rekluse a bit, and try the pilot screw at 1.5 out.

Do you guys think I could run a 42 pilot? I've done numerous searches and it looks like most people run the 45 as a pilot on the '09.

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