Mid range bog

[bueller416]

I live in northern KY.and have a 2005 KDX200 with the following mods.155, 45, needle in the third clip from top, Air screw 1 1/2 turns out, drilled air box lid, FMF woods pipe, and boysen reeds. The throttle response off idle is great and it runs great on top end.The mid range has a slight bog/hesitation especially in 3rd and 4th gear. I'm just looking for suggestions on which way to go to try and smooth this problem out.Don't get me wrong the bike runs great, I would like to get rid of this slight bog/hesitation if possible. Also will a aftermarket air filter improve anything over the stock one?
Thanks,Jeff

 

[Rhodester]

Things to note: Is the problem worse when the engine is cold or warm? After the bike is warmed up good try pulling the choke on when riding in the "bog" range and see if the problem gets worse or better. Those tests will tell you if it's a lean or rich condition that you're dealing with. My guess is that it's a lean hesitation (without any other info). The first thing I'd try (assuming it's lean in that range) would be to raise the needle (lower the clip) one position. That'll probably fix the problem. The next step would be to change to a different needle profile altogether. With the stock slide I'd try a CEM or CEL for smooth but stronger than stock response. If you want snappier response (especially bottom end snap) I'd go with a DEM or DEL. I'm running a DEK/3 with a #7 slide and it's great. The difference is dramatic enough that I'm going through back tires faster than I ever used to.

 

[John Harris]

Just to make things interesting for you, I am going to guess that it is a rich bog. I suggest putting the needle clip in the next to the top position, and that that will cure the problem. If that does not get it then try a 42 pilot jet. Yes, all bikes are different and you should jet properly using the prescribed proceedure, but i suspect that you are really close and will know when you have it right. Yes again, the different slides and needles will work, if you have time to sort them out by trials and errors and errors, but you can get the stock to performing very well.

Rhodester forgive me for disagreeing with your conclusion, but your test is right on!

Ride safe and have fun--John

 

[hart125]

I have a 99 with the desert pipe and the exact same problem. the bog is most noticable at half to three quarter throttle. I know it's a lean bog but my plug is perfect and I don't want to loose gas mileage by raising the needle.. I ride gravel roads a lot. So I'm looking for the ideal needle I think.

 

[Rhodester]

hart125, your gas mileage will still be great if you raise the needle. It'll only make a very slight difference in mileage. Who knows, you may change your riding technique along with the proper power change and your mileage may actually improve! Remember, a plug chop test (if that's what you use) is usually (but not always) done at WOT. So your plug will look exactly the same no matter what your needle position is. What's your jetting, elevation, and usual temperature that you ride in/at?

 

[hart125]

I'm at 42/1174middle/155 with fmf desert/boyesen power reeds and open airbox...and it is great except at certain times I can notice that slight bog at 1/2 to 3/4 throttle. I'll try again to go to the 4th position but that makes the idle so rich it will start with no choke with a 40 pilot! That makes me nervous. I also never hear of people going to the 4th position..Can you recommend a few needles that may give me the richer taper I'm looking for? Thanks!!

 

[Rhodester]

Try a CEM/3. The Cxx series of needles have a slightly steeper taper angle but the taper starts lower on the needle. This means that the tapered section will have less of an effect than the Bxx (stock) series of needles at idle. It will also be slightly richer when you get the throttle more open...toward the tip of the needle (your trouble spot). The Dxx series of needles do this even more so.