Ok folks so i recently bought a 2009 KLX 250sf from a dealership, and i am just about at my limit before i throw this thing off a cliff. It was used with 5 miles on the bike which makes me wonder. not under warranty of course. Here is my problem.

The low end of the RPM is HORRIBLE. It wants to bog out and die when i run a low rpm around 2-5k (flooding?). It seems to be running well enough if i stay at high rpms aside from a slight hiccup when running a steady cruising rpm of 6-8k. Sorry for the long story but i will try to be as detailed as i can and this is my first time working on a bike like this.

I am at 8000+ ft elevation and I have taken this bike to get jetted by a local kawasaki mechanic. We purchased a klx300 jet kit for it since that is what I'm seeing a lot of people do for power. The mechanic spent hours working on my bike to no avail and returned it to me with all the stock pieces back in it. Said he could not get it to idle with the jet kit and that he tried multiple variations of the provided needle and main jets. Also said the 124 main had a ton of black smoke coming out (making me think too rich).

So i took it home and personally tried a few settings with the needle from the jet kit and keeping the stock 35 pilot and 118 main. I felt it was running best on the lowest fuel clip setting (the one closest to the top). The bike will idle but easily floods when a slight crack of the throttle. With this setting i basically cannot run below 4-5k rpm because the bike will try to bog out and die as if it were flooding. I then have to open the throttle while starting to get it back to an idle. If i punch on the fuel to start i can get it above that rpm range and run through the gears seemingly well enough.

Thinking my problem is either in my needle or pilot jet i ordered a #38 pilot and some smaller mains to bridge the gap between the 118 stock and the 124 which the mechanic said would not run. I have now installed the 38 pilot and a 120 main. I tinkered around with the needle with these new jets and i have now basically given up on the aftermarket needle. Tried clip positions #1, 2, 3, and 5 from the top. all seeming to have the same problem (low rpms / cracking the throttle results in flooding) I currently have the new jets in and the stock needle in with no washer on the needle and i can actually crack the throttle to 2-4k rpm in neutral BUT it fluctuates that low rpm when i am keeping a steady hand on the throttle /boggle (with the washer on the stock needle it seemed to act more like the aftermarket needle with the bogging out). I can now engage first gear at 2k rpm and get moving but when i hit the gas it is still hiccuping / jerking a lot at 3-5k and it slowly gets out of that rpm range to where it seems to run better. If i take it to the 3-5k rpm range where it is bogging and let OFF the throttle it does not go back to an idle it will just die. I then have to open the throttle while starting to get it back to an idle.

I am trying to do some fun trails and some treacherous hill climbs in my area that are going to require some low rpm power and this is not going to cut it. I can't even drive around town in a low rpm without looking like a fool, it jerks me around like crazy just trying to putt along. Any gear i dip below 4k rpm is bogging and barely making it back up to accelerate.

So now the last option i can think of is a smaller pilot for my altitude might make sense but i cannot find a smaller pilot for the bike and have never heard of anyone using one. Then the final suggestion which the mechanic mentioned is that my carb needs replacing, and thats just a guess. He mentioned something about possibly a faulty idle circuit that i don't understand at all. I don't want to replace a brand new carb on a bike i bought from a dealership to have that not be the problem as well. I would like to run an aftermarket needle for more midrange power but i can't even get past the low range problems with it. Another friend mentioned timing which i don't understand much about either.

So, did i buy a complete lemon? or the wrong bike? I LOVE the size, and the power is not a problem if it wasn't for the low end problem I'm having. Really want to get this thing running so i can start hitting some trails. Please any help or suggestions greatly appreciated.

P.S. I've had the air box lid OFF (as the jet kit recommends) and just the snorkel off for most of my testing. Either way yields nearly the same results. I will try to post a video of my problems if i can figure it out.

 

With all the work you done on it, the first thing I would do next is put a new plug in it.
Next thing I would run the engine with the air boot off and see if the slide is moving up and down when you crack the throttle, maybe the diaphram has a small hole or defect in it.
Check your actual float level height with a hose on the drain plug.
Sounds like you changed all the jets, etc. so they cannot be plugged up, although some passage may be clogged.
If everything passes there, take the carb out and tear it down and boil it in water for an hour.

 

What happens in the low rpm range when you change the position of the pilot screw?

A possibility for the low rpm problem is that the carb is running off of the needle/main jet circuit instead of the pilot circuit. An indication of this is that the pilot screw has little or no affect on the engine.

You say the air box lid is off.....has the exhaust also be opened up? Getting more air in won't help if it can't get out after combustion.

Ride on
Brewster

 

Has the fuel level been checked on this carb? And by that I mean the actual fuel level in the bowl using the clear tube method and not the static measurement of the float with the bowl off.

 

Ok after over a weeks worth of searching i stumbled upon this page and it almost seems like its speaking directly to me and may be my problem.

CARB CLEANING

"My KLX-300 has been in storage for several months. It starts OK, but when I give the throttle a twist, it stutters or bogs down before revving up..."

"The carburetor has three transition ports in front of the throttle plate. They are not adjustable, and not usually included on jetting graphs, but if they were, you would notice that just past idle, the fuel air ratio is almost entirely dependent on these ports, and can therefore cause the bike to stutter or stall if totally plugged."

So Tomorrow i will be trying to clean these ports with carb cleaner and possibly boiling it as durielk recommended.
Before i do this i will attempt to check the float level. I assume you just bend a clear tube up from the drain to check the level. what is it support to be at?

The diaphram appears visually to be in tact and looking good on the seal every time i open it up. But i may check that its moving up and down.

When i changed the pilot screw to 38 i honestly don't think i noticed anything. might have a stronger idle and i turned the air fuel screw in at the same time i changed the pilot so it didn't have much effect.

The exhaust is all stock. should i take the tip off for more airflow at this altitude? Im thinking one day i might get an aftermarket exhaust but right now all i can think about is getting it running properly.

 

I run stock exh with pumper carb. With this carb, when I took the top off the air box, it ran pretty much like your problem, if whoever took that off and did not make drastic changes to the carb, then that also may be your problem. I may be easier to just try it with the cover on, than going through all the hard stuff.
I like to check the easy stuff first, no need to tear every piece apart in the shop if it is something simple.

 

stock with the snorkel and cover on it was not as responsive when giving it a lot of gas. with the snorkel removed it was noticeably better and with the entire lid off it was definitely too lean and you would feel the lack of power top end. With the addition of the larger main and pilot i think the lid off has the best feel right now.

 

Hmmm...a mechanic worked on the carb, and the first thing he didn't do was insure the carb was thoroughly cleaned out? Some spray carb cleaner, maybe a small wire from a wire brush, and some compressed air are usually the first order of business, followed closely by a proper fuel level setting. If a glitch in either one of those major issues to always be considered in rectifying and/or jetting a carb aren't correct, you can chase your tail forever.

 

An 09 with 5 miles, maybe old/stale tank of gas?

 

The 5 miles on the odo and being a "used" bike sounds fishy if the dealership is claiming that. If it was a damaged/replaced instrument panel or such, that would be different, but they should claim such if it's the case. If it's an '09 sitting on the floor that long...also hard to believe...why wouldn't it have warranty? Anyway, on an unknown entity like that bike, the first thing you do is clean the carb thoroughly...period. Now, I'm making the assessment on the aforementioned mechanic based on the post where the OP mentions the plugged carb post. Sounds like the OP was told or is aware the carb wasn't thoroughly cleaned...or that maybe just the aforementioned mechanic didn't do a good job of cleaning the carb.