Bog off idle & weak midrev, jetting specs inside thread

[camrider]

I have a 2003 KDX 200 with stock engine (6hrs on very first New top end), Gnarly torque pipe, torque reeds, open airbox, OEM filter, OEM stock needle, 45 pilot and 155 main, air screw 2 turns out.

The carb is sqeaky clean as are the jets and airways. The fuel is fresh 93 octane mixed with Yamalube at 32:1.

I'm in Georgia and our temps this weekend were near 70 degrees. We took a stroll at a local offroad park and the bike runs well in the higher revs, but it will bog if you blip the throttle from idle. It also feels a bit weak in the middle. I tweaked the air screw from 1.5 - 2.5 with no noticeable improvements.

Any help?

Do I need to go leaner on the pilot and change to the CEL needle, OR ?

 

[agitt73]

id go with a 42p and lower the needle 1 clip (raise the clip up 1 notch)
forgot air screw should be good at 1.5 with the 42p

 

[John Harris]

What aggit said above. Clip should be in next to top position on needle. Should snap with those settings. Ride safe John

 

[canyncarvr]

Re: '6hrs on very first New top end..'

What is the state/status of the KIPS?

There is a specific action during dis/re-assembly that can damage it...and give you exactly the symptom you have.

 

[bmcd308]

I've heard lots of mention of supporting the KIPS shaft when reassembling, but I have no idea what exactly that means. I have the factory service manual, but it is not real clear that there is anything I need to be careful about. Can anyone point me to a good explanation, preferably with pics? I've done a 2t top end before (well, I've been right there when someone else did one), but I've never done a KDX top end.

 

[canyncarvr]

The KIPS shaft must be supported....during take-apart AND put together.

There is a FLAT on the shaft (the shaft between the crankcase and the cylinder) that allows for a wrench to be used for that support. USE it!! The point is to put ABSOLUTELY NO FORCE on the activating spring assembly (in the case) while wrenching on the LEFT HAND THREADED nut that holds the gear piece on the shaft.

If force IS allowed to reach the bottom activating assembly, it WILL be damaged.

The results of that damage vary from a seemingly bad tune that you cannot cure with any jet combination to complete destruction of the engine.

Oh...you will need to scrunch the boot down the shaft to get TO that flat. It's there. Find it. Use it.

This isn't a great big deal to get done..but it is certainly, absolutely, and most indubitably necessary.

...and may be what did NOT happen in this case.

 

[camrider]

Re: '6hrs on very first New top end..'

What is the state/status of the KIPS?

There is a specific action during dis/re-assembly that can damage it...and give you exactly the symptom you have.

Not sure what you are reffering to, but the KIPS was cleaned and timed correctly.....?

 

[mideastrider]

Just to be sure remove the cover on the side of the cylinder and make sure the KIPS is working.

 

[canyncarvr]

The post times are close....maybe you missed the 'shaft support' part? The part quoted implies that....

Please...read the 'shaft support' post..post #6.

BTW..removing the cover on the side of the cylinder (either side..left or right won't matter) will NOT tell you the KIPS is working. Not all of it anyway.

 

[camrider]

The post times are close....maybe you missed the 'shaft support' part? The part quoted implies that....

Please...read the 'shaft support' post..post #6.

BTW..removing the cover on the side of the cylinder (either side..left or right won't matter) will NOT tell you the KIPS is working. Not all of it anyway.

Yea, I think I was typing at the same time you were. I used the flat spot as recommended several months back when I rebuilt the top. I had already searched here and read as much as I could find before tearing into the engine. So I don't "think" that is the problem.

 

[mideastrider]

BTW..removing the cover on the side of the cylinder (either side..left or right won't matter) will NOT tell you the KIPS is working. Not all of it anyway.

True, but you can tell if its moving the governer shaft. I have saw the lever on the bottom of the governer shaft wear/break off. No sense tearing the top apart if its in the bottom. Just something to check.

 

[camrider]

I know that the KIPS itself is working as I tested it by rotating the shaft by hand before I put the engine back together.

 

[ridejunky]

I know that the KIPS itself is working as I tested it by rotating the shaft by hand before I put the engine back together.

Yes, but as CANYNCARVR was saying, if you don't support the actuator shaft when removing the actuator arm assembly apon doing a top end you will damage the advancer below the shaft near the clutch.

 

[camrider]

I understand. I read my manual thoroughly and searched here before tearing down the top end since I had no experience with the KIPS system. I supported the shaft with a pair of channel locks while taking the nut loose (reverse thread) and while reinstalling the nut. I've seen several posts here about people either damaging internally or braking the shaft from not supporting it properly.

"IF" someone damaged their advancer, how would you know positively if the advancer below the shaft was damaged or not?

 

[ridejunky]

In your case, since you are experiencing poor low-mid end performance, you valves would be stuck open. If you pull the exhaust off and the kips cover off, you can shine a flashlight in the kips cover and if you see light in the exhaust port, it's damaged. otherwise you would have to disassemble to visually inspect.