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KTMTIM2006

CRF150R Lean Bog

13 posts in this topic

Just brought home the new 150, and started it for the first time, and it ran on the choke fine during th warm up period, I pushed the choke button all the way in and blipped the throttle and the bike appears to have a severe " Lean Bog" I played with needle settings and air screw adjustments with no luck does anyone know the fix, so I do not have to recreate the wheel , Thanks

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We are in NY and ours was lean for here also, bogged weather you were riding it or it was in neutral. We went to a 45 pilot and it was better but a bit rich at that piont so we ended up at 42 pilot and 138 main. It idles smothly with the fuel screw at about 2 turns out. if your tooling around on the trails and really rap the throttle it still would bog. Did the o-ring on the accel pump and it did the trick. in neutral it will still bog(naturally) but riding it will not, not even when lugging at slow speed and then twist it. The manual jetting chart shows a 40 pilot for all elevations and temp!! maybe a misprint

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The quick shot didnt help ours much at all, the pilot jet and the o-ring on the ap made the most difference.

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145 MJ, 45 PJ, 2 turns out on FS. I also had to bump up the idle a tad. Now she can start it even off the center stand in one or two easy kicks.

ben

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On the side of the carb there is a blask cover over the area where the cables mount. Remove the cover and you will see twards the bottom, an adjuster screw inside a spring. Turn the throttle and you will see that the screw moves away from the ap arm and allows the spring move the arm along with the screw. If you open the throttle quickly the ap arm lags behind. Put a rubber or neoprene o-ring around the two of them to help keep them together. The o-ring takes up some of the lag reducing the bog. Some guys wire the ap arm to the screw so that the arm and screw move together in real time. The 07 crf 450's (so ive heard) have a linkage on the ap so there is no lag. You can also tune the ap with different size leak jets. The bigger the leak jet the more fuel is passed back into the bowl, less fuel into the carb and less resistance on the ap meaning less lag. It also changes the duration of the squirt. The adjuster screw times the start point of the squirt. Trun the screw in and the squirt starts later, out starts the squirt sooner. if you start the squirt too soon the fuel hits the back of the carb slide, too late and you may increase the effect of the bog. You will not get rid of the bog while its in neutral, almost any 4 stroke wil quit if you wack the throttle fast from closet to wide open on the stand. Our 150 takes about 5-7 minutes to completely warm up so make sure your bike is up to temp before adjusting or making any evaluations, and go by how it responds while riding only, not on the stand or you will chase your tail. I hope this helps, i asked this same question about a month ago and the answers i got were not helpful and i didnt get a reply on the leak jet questions i had, so these findings are all from observations that i have made and adjustments that i have tried.I got the o-ring trick from a post in the 450 forum.And also save your money on the boyesen quick shot, it didnt make much difference in the bog, and maybe gained a little bit of throttle response when rolled on smoothly, but not $90 worth in my opinion.

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