HELP! 2005 CRF250 Throttle problem

[heimchr]

i have a 2005 crf250 and when I blip the throttle the engine dies or hesitates for a second. It has a dead spot. Any Idea what the problem could be? I have changed the main jet and it does it with both jets...no difference. I thought maybe it was running lean, but it isn't according to the spark plug. I even put a boyesen excelerator pump cover on it, which is suppose to elimate hesitation or bog. I also have a white bros carbon pro exaust system. Does anybody know what would cause this hesitation. Let me know if you have any ideas. Thanks

 

[2-Strokes 4-ever]

I had a 4 stroke for a short time, so my REAL experience is only limited. I do know that the 4-strokes are not responsive to "blipping" like a 2-stroke, and may never be. If it coughs and dies when under a load (riding) then that's an issue to deal with, but it sounds like you did the right thing with the accelerator pump cover. The pilot jet is what effects initial throttle openings. For me, a 4-stroke was almost like learning to ride all over again........I learned "rolling" the throttle on was best.

 

[Moto Squid]

changing your main jet wont change anything off ide...thats the pilot jet and fuel screw you need to tinker with. Get a zip ty fuel screw since its long and you can just reach under there and adjust it. Once you get your pilot/fuel screw adjusted that boysen pump cover will be able to work properly.

 

[heimchr]

hey guys thanks for the info......i will look into the zip tye screw. If you can think of anything else please let me know. thanks

 

[2-Strokes 4-ever]

And........on a 4-stroke the screw is a "fuel screw", not an "air screw." For your bike, turning it out will richen the mixture.......which is the way it sounds like you need to go.

 

[biglou]

I'd go leaner. I think the 250F's have an accelerator pump like the 450's do. It squirts a stream of fuel down the intake tract when you twist the throttle. A rich fuel screw can compound this. Run it all the way in, and back it out 1.5 and go from there. A Zip-Ty fuel screw won't change anything, just make it easier to adjust (and they are worth the money, IMO).

Another note, don't gage throttle response of a 4stroke on the stand. All of mine had some sort of stumble at times on the stand, but ran fine on the track. Go by how it performs when riding it. And roll the throttle on when reving it on the stand. Get the R's up a bit, then blip it. It should respond that way.