Hey all,
Picked up a kx450f 2006. Really really good condition still had stock tires till i added black rims.
Anyways when i bought the bike noticed it poped and backfired, so i changed the stock jetting and put in a 55 leak and a 45 pilot. Cleared up the poping amazingly!

Only one problem, when it was running lean it started 1st freakin kick hot or cold! That easy! Now that i richened it up it does not seem to want to start.

Put a adjustable air/fuel screw on it and at 2 full turns out it runs good, idle does not hang, no popping or anything. But i did notice if i snap the throttle from none to 3/4 it will bog and or sometimes die..

When i adjust the fuel screw if i go in more the idle will hang then drop back down after every rev.

I jusT dont understand how changing the pilot, leak, and airfuel screws out that it could cause this.

My starting techniques are cold: hold kill switch kick 5 times, find tdc and kick.
Hott is tdc, hot switch and kick.

Sometimes if i give it a little Gas itll fire up little easier bUt not much.

Im talking 5-10 kicks cold, 3-8 hott..

My air screw is 2 out and idle a little higher then stock.

What do you guys think? Valves couldnt of gone out of spec that much from just changing jets..

Thanks! I do have a pro circut slip on and im at roughly 50-150 ft sea level

No choke when cold?

A higher idle usually means harder starting, but less stalling in corners of course.

I have never used the kill switch and kick method, I always (on a carbed bike) pull the choke up, twist the throttle once or twice, find TDC, then kick.

D-K, on 04 July 2012 - 12:05 PM, said:

On my 06 I started mine close to what D-K does. The first time I start it for the day I would kick it over 2 or 3 times slowly,to make sure every thing is oiled,then blip the throttle twice,then choke,find TDC and kick.
When hot I would put in neutral,  find TDC , pull hotstart lever,kick(harder is not always better,smooth medium speed ,it's not a 2stroke)

Hope this helps

Ernie

175 main
45 or 48 pilot
NCVS needle third clip
remote fuel screw (R&D)
50 leak jet
merge racing apump linkage spring upgrade (do this to eliminate all bogging)
adjust apump timing to miss the slide (if it hits the slide, you will get a false rich pilot symptom)

Adjust your fuel screw for highest possible idle with quickest possible idle drop.
Adjust idle (drop it) with idle screw and repeat.
It will take 1/8 turn fine adjustments to find the sweet spot.
When you find that spot, you will know. More throttle response. There will always be a little bit of a' burble' on decelleration.
If the screw is more than 2.0 turns out, you go smaller on the pilot jet
Less than 1 turn you go bigger.

The 06 carb is pretty good with stock jets except use the 55 leak (instead of stock 75).  07 and 08 carbs might be slightly different.

I used a 45 pilot for a while, with screw at about 1.5 turns. But I went back to the stock 42 (a new one) and screw at 2.5 for slightly easier starting.

If your carb starts doing weird things, then I suggest you put in a new pilot jet (42) since they are cheap and they often clog with age. The whole AP system also needs maintenance about once a year, but that wont help starting of course. With the carb still on the bike, but the subframe and airbox off, you can put in a new AP diaphragm, lube and clean the AP rod, and tune the AP screw. I set my AP adj screw so the pump rod moves as early as possible and that works for me. I just put one finger on the end of the rod while I turn the throttle and go by feel.