Throttle hesitation off idle - 2003 kdx 220

[bassmaster]

Just purchased a 2003 kdx 220. Bike was completely rebuilt by a friend of mine who knows what he's doing. Bike is completely stock (other than replated cylinder and wiseco piston). Bike runs great except..........off of idle it hesitates (just for a second) when you crack the throttle. It is very noticeable. Within a split second the revs start climbing like crazy; but the split second of.......nothing........really throws me, and I don't like it at all! I checked out the KIPS assembly and it's functioning fine. I have been messing w/the air screw in 1/8 increments and it doesn't do anything. I've tried new gas (mixing it at 32:1), with no effect. My friend had completely cleaned out the carb before I bought it from him; but sure seems like it maybe a clogged pilot jet or something. Any advice would be very appreciated.

 

[_JOE_]

Sounds like it very well could be a restricted pilot jet. It's worth a look at least.

 

[sr5bidder]

your idle speed may be set to low (try raiseing the idle speed and then turning the air screw in to richen a bit)

or the air filter may not be oiled enough or have a leak between the filter and the reeds

 

[julien_d]

Air leak is possible. Is it a hollow sounding bog or does it sputter? An air leak,aiscrew adjusted too far out, or too small of a pilot jet / clogged pilot jet will cause a hollow sounding off idle bog. You want to adjust the airscrew on a KDX for best off-idle throttle response. This is rarely anything close to the traditional "fastest idle" setting for the airscrew.

 

[bassmaster]

It's not a hollow sound or a sputter, there is just.......nothing........for a split second, and then the beast comes alive. Tough for riding - I currently have to plan on the fact that when I come into a corner, and if my rev's aren't up, and I just crack the throttle, I will have a split second of zero power. It is not good.

On a side note - does anybody know what the little steel bar is for that is welded onto the right side of the frame under by the silencer - is it supposed to be a handle to aid in lifting the bike (doesn't work well if that's the case)?

 

[sr5bidder]

the the question has come again boys....

I thought we made it clear last time the small bar is for the optional accessories..side car, trailer, or cultivator (must purchase the right hand rear sprocket/ brake disc for cultivator drive)

 

[sr5bidder]

I think its time to reclean the carb and check the needle clip position..

does it idle well?

 

[reepicheep]

It works great for lifting the bike, you just haven't wrecked in deep enough mud to appreciate it yet! ;)

 

[julien_d]

uh. "nothing" as in the engine turns off? Because if the engine is running, and you're giving it throttle, "nothing" isn't really possible. There has to be SOMETHING. There's vacuum there, and a running engine. Pay really close attention next time you ride. Is it kind of like buhhhhhhhhh before it hits and starts ripping again?

At this point I still can't narrow it down.

air leak
clogged pilot
pilot is too small
airscrew is too far out

Or I'm completely off base and it's way to rich. However I have a feeling it's one of the former four options.

 

[Dirtdame]

Another thing that will cause that symptom is a mistimed or sticking power valve. I had an old KDX cylinder replated and there was a lot of metal debris left in the cylinder especially in the exhaust port/valve area. Try as I might, I could not get all of this stuff cleaned out of there on the first try. I thought it was clean and reassembled the engine. When the bike didn't run right, I checked the valve and it was sticking. I had to clean the passage where the actuating rod fits two more times to get the rod to quit sticking and have the rod work smoothly. :nod:

 

[julien_d]

good point ^. If the valves are stuck in the "open" position you will have a serious lack of power on the bottom end.

 

[bassmaster]

I'm trying to post a link to youtube to a video of my bike revving; but 'spamkiller' is not allowing me to put the link on a post. Is there a way around this (as I've seen many links on threads - how do you do it)?