KDX hesitation issue

[bmonnig]

Guys,

     I've got an issue with my '00 KDX 200 that's been bugging me.  Some friends and I were out flat-tracking the bikes in the mud today, and this issue came up again.  :think:     

     After running for a little while (say 5 minutes or so), when accellerating hard on the pipe, the bike will just "die" out for a split second.  It feels *just* like you temporarily interrupted the fuel supply.  It's enough to really throw off your concentration, or maybe put you in the dirt mid-corner. 

     It appears only to do this after a couple of laps (running 5 minutes or more), when warm, only under a load, only when on the pipe, and only accelerating.  When it starts to do this, though, if you slowly roll off the throttle the "bog" will follow you down.  If you chop the throttle off for a second and re-hit, it's fine. 

     It seems like it takes a while for the first instance to occur, but after that it will re-occur with more frequency.  Stopping the bike for just a minute or two will make the symptom go away until you put another several laps on it.  

     I noticed today that you can also hear some "noise" in the engine when it hesitates like this.  I don't know how to describe the noise, other than it sounds like a KIPS valve rattling.  That may be exactly what it is.  This noise isn't around at any other time.  I might just be hearing the KIPS rattling because there isn't any combustion noise/pressure to mask it.

     It was doing this prior to re-setting the floats, so I don't believe it's a float height/needle issue.  It's not the tank vent (removed and still did it). 

     I've not completely removed the petcock as a culprit.  It's definitely had this hesitation with the petcock in the "on" position, but I didn't get the problem to come about with the petcock in the "res" position.

     It did it with the stock pipe, and now with the Pro Circuit pipe.  Stock silencer on both pipes.  It has fresh gas, mixed 40:1 with Motul 800.  Good plug. 

     I'm currently thinking it's a fuel delivery issue.  It just "feels" like a fuel issue, and I wonder if there's some debris on the pickup for the "on" position of the  petcock. 

     If this sounds like any other "I've had that before!" issue, I'd appreciate any help.  My next course of action is to remove/clean the petcock/screens/pickup.  I'd just like to nip this as soon as possible, so if you have input (prior to me tearing into it), I'd appreciate it.

Brandon

 

[23jayhawk]

Pull the fuel hose off the carb, and time how long it takes to dump about a quart of fuel into a coffee can on MAIN. Then time the same amount on RESERVE. That should eliminate whether the petcock is the problem.

 

 

 

[Brian]

Something similar to this has happened to me before. I went crazy trying to figure out what it was. I checked the petcock, fuel filter, etc... It ended up that my carb breather hoses were clogged with mud. This may or may not be you're problem, but it's worth looking at.

 

[gooby]

You might want to look at the floats again.If your doing extended on the pipe flat tracking,it still may be fuel recovery in the bowl.The noise you hear is because it's lean at that moment....you let off...it runs on,then it recovers and is good again imo.Raise the height a bit if you find no other issues in the fuel system?

 

[GREENHORNET]

HEY-- I WOULD TRY A NEW PLUG-- IT MAY OR MAY NOT BE THE PROBLEM--- WHAT ABOUT YOUR REED PETALS ARE THEY IN GOOD SHAPE

 

[limitless]

it sounds to me as if you need to dial in your jetting

 

[91KDX]

I have had that problem a lot too. I just rode my bike back home from my neighbor who built me some new muffler and scilencer mounts, and my bike did that same thing. I believe it was because the bike was cold, I was low on fuel and I had all of my overflow tubes angled up and resting on the rear shock to keep it from leaking on my neighbors garage floor. Thats not the only time I have had this problem though. I haven't found the solution to the problem though.

 

[RJ-KDX]

I had this same problem today riding. After warm up, if I wacked the throttle it would bog for a split second then take off.

Now to rule out a few things, the bike was clean, meaning no dirt in the over-flow tubes, and the jetting is pretty close (IMHO). If I stayed on the throttle, there was no problem of course. It's on initial take off or after coming to a stop.

I rode all day with this condition, it wasn't every gear, but it was annoying. The bike ran like a champ. I'll report back after my post cleaning. :thumb:

 

[limitless]

RJ - try moving the needle clip 1 position (richer)?

 

[RJ-KDX]

Originally posted by limitless
RJ - try moving the needle clip 1 position (richer)?

Can't, already at the top. :whiner:

 

[WoodsRider]

Top position is lean, the needle hangs down further in the main jet. Move the clip down to raise the needle and richen the air/fuel mixture.

 

[RJ-KDX]

:( my bad.

So you think it is running lean? My plug is a nice tan color. I was running too rich before. Hhhhmmmm........

 

[23jayhawk]

What you are describing is an off-idle lean bog.  And it's not helped by the stock needle. My understanding is the lean 'Q' diameter on the 200 needle can cause that flat spot at part throttle.

 

[gooby]

Even with a tan plug,you still may have a zone that is lean.In my other reply i assumed the guys had the jetting right since it was not mentioned.So i figured it was a fuel flow problem, with this additional info it problably is a jetting issue then.Either way it sounds like a lean bog to me.

 

[WoodsRider]

If it's bogging then it's too lean. Raise the needle one notch at a time. If notch #2 from top is too rich, then you need a leaner needle. Personally I'd rather be rich than lean. Never squeaked a motor by running it rich and I'd rather clean spooge than rebuild an engine.

 

[RJ-KDX]

All points taken. :thumb:

Thanks all.

 

[limitless]

Also, I might point out that it is not good for you to be correctly jetted with the needle on the top or bottom posistion. It is not bad for any other reason than the fact that you can't adjust it. You want it correctly jetted with the clip position on 2-3, that way you can adjust if the need should arise.

 

[GREENHORNET]

I thought the needle was effictive from 1/4--3/4 throttle
what about the air screw and pilot cicurit?

 

[galena]

91kdx subscriber ,I am from Rochelle,il and was just wondering if you live close by it never hurts to have another rider join the crew for a fun day of riding Galen A.

 

[91KDX]

I am originally from West Chicago (everyone knows where Wheaton and Winfield are but nobodies ever heard of West Chicago). My family moved out to Kirkland last winter. We moved to a small farm that needs a ton of work, but we have 7 or 8 acres that I can ride on, we have acouple of horses, chickens, dogs cats, and all that stuff. My brother has a 4 wheeler that never runs so usually I ride by myself. I have a ton of trails and stuff going all around here that just my buddies and I ride on. I race HS and this Fall I start enduros so maybe we can meet up somewhere.
Benjamin

 

[galena]

Hey sounds great Benjamin,I only live about 20-minutes from Kirkland,staight east of DeKalb 16 miles.I have a buddy that want me to go race the HS at Morrison,IL with him this spring.If you want e-mail me and see if we can work out a time to meet and do some riding.My e-mail address is galena@rochelle.net spring is just around the corner!can't wait to hop on the good old green machine and turn some dirt! later.Galen A.