XR650R fuel screw adjustment/stumble

I am trying to fix a stumble my bike has when cruising at medium revs (55-60 km/h in 3rd gear - 15/48 gearing) the bike pops/stumbles when on the low speed jet. I have tried adjusting my fuel screw everywhere from 1 through 3 turns out and nothing seems to get rid of this. Do all XR650R's do this? Am I being to picky or can this be sorted? I have a 68S slow jet, 4th pos on B53E needle and a 175 main at sea level.

My guess is you are running too rich - try a leaner main jet,(easy to get to), first. My bet would be a leaner slow jet.

I'm setup the same except I run the needle in the middle (3rd) clip position. Main jet only effects above 1/2 throttle. You can check if your running lean or rich. Reach down and close the choke slightly, if it runs better then you were running lean, if it runs the same or worse then you are jetted rich.

I went to my Honda dealer. They gave me the "SHOP TALK" sheet from Honda made for the mechanics. It says to use a main jet part # 99101-357-1750, and a needle part # 16012-MBN-641, and the stock slow jet. The needle should be in the 4th position, and the fuel screw 2 1/2 turns out. So I put the stock (65S) slow jet in and turned the fuel screw 2 1/2 turns out. Voila! Bike starts better and cruises more smoothly. I am at sea-level. I hope this helps somebody.

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