carb question: choke and pilot jets

I have a 2001 YZ426. It runs alright but has a ton of decel pop when i let off the gas at just about any rpm. From what I gather this means the pilot jet is too lean, it had a stock 42. I replaced it with a 45 and it may be a tiny bit better but its still bad, so i need a bigger jump. I noticed the bike has pretty much no popping when i have the choke on, and still runs pretty well, so instead of just buying one jet after another, does anyone have an idea how much of a jump in pilot jet size it would take to equal turning he choke on? Should I try something in the mid 50s? Higher? Is that just too high?


Before you turn your bike into a plug fouling gas guzzler that stalls every time you drop the throttle too quick and becomes an enormous PITA to hot start, you should check your exhaust system for leaks at both ends of the header. You should also be sure the carb fits snugly in the isolator and that there are no air leaks in the intake, and that the hot start plunger seal is OK and the plunger fully closes.

Once you've either fixed that or verified that it's OK, then you need to judge the pilot jet based on how the idle circuit sets up, not by whether it pops on decel (it should pop some).

Making an analogy between the choke and the pilot circuit is difficult since the two circuits in the carb feed air from different sources, but the starter jet is normally around a #70, which is roughly double the fuel flow of the typical pilot jet.

Thanks for the tips, I ordered both new exhaust gaskets just to be safe, and I'll check all the connections today to make sure no air is getting out. That would make since as I don't remember the bike making so much noise when I first bought it, but then I spent so long not riding it that I really couldn't remember.

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