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06 KLX250S Jetting?

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Anybody done any testing on a 2006 KLX250S? I'm at sea level & would love to open the air box. It's my wife's bike, & it needs help. It's very hard to start when cold (full choke). Can I drill & adjust the fuel/air mixture screw to alow me to at least remove the snorkle? Any help would be appriciated. P.S. I already know about the Kaw.forum. I only trust TT.

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adjusting the fuel screw will help starting and idle.may need a biger pilot jet if you end up 3+ turns out.

air box mods may require bigger main jets.

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My wife's KLX250s has been hard to start when cold from the day we picked it up at the dealer brand new. It starts fine once it is slightly warm. Now that the weather is colder, she runs the battery almost all the way down before it will start from cold. Full choke, no throttle. 1000 ft elev. No mods.

I am going to adjust the fuel screw today and will report back if it helps.

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I just started taking all the stuff off to get to the carb so that I could drill and remove the cover from the fuel screw tube. In the process, I was trying to find a vacuum line to the petcock that would stop fuel from flowing when the engine stops when the petcock is left in the "ON" position, like the one on my DRZ. I did not see one that looked like the one on my DRZ?

While looking for it, I started thinking that maybe we were supposed to be turning the petcock "OFF" when we stop riding the thing. Maybe this is why it is hard to start when cold? So, I turned the petcock to the "OFF" position, pulled the choke/enricher all the way out, and it cranked right up. Put the petcock back to "ON" and it kept running just fine. I killed the motor and re-started it with the petcock on and the choke/enricher on, again no problem at all? So, now I am going to leave it alone and see how it does if we turn the petcock off after every ride.

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OK. I give up. The "Off/On" Petcock doesn't make any difference. Since posting my last remark, I have tried it many times. I have found that my battery is defective. It goes to 9volts when a load is put on it on a tester. A new one is coming in today under warranty. There are no motor/airbox/exhaust mods on this bike. Snorkel is in place. Air filter is fairly clean and oiled.

My attempt to solve the problem...

I adjusted the fuel screw, which was at 1.5 turns out from the factory. The fuel screw does affect idle when screwed in, but not much when screwed out to 3+. The motor runs highest rpm at 2 turns out when fully warm.

At 2 turns out with choke, it still would not start from cold easily. I turned the screw to 3 turns out just to see what would happen on a cold start. I let it sit overnight in sub-freezing temp. I tried to crank it this morning with the choke on, it starts to run almost immediately, but then dies just as fast and won't stay running.

I pulled the carb to see if it had a "starter jet", so I could try to go bigger. It has a pressed in starter jet. Is there anything I can do to help this? Eddie, will the bigger pilot do the trick?

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Let's say the initial start was "better". It still took a few seconds. When it does start, it dies. Then I can get it to start right back "easily", but then it dies again. It will do this over and over until the battery is drained. (New battery will be here today). When I had the fuel screw at 2, it would eventually start and would stay running.

Will a hotter spark plug help? It has a NGK CR8E in it.

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With the screw at 3 turns out, If I hold the throttle open a little, then yes it will stay running. If I release the throttle, then it dies. After it gets warm, it will start and run without the throttle being held open.

What I did yesterday in my quest to solve this...

I pulled the plug to take a look at it. It was completely black except for the very edge of the electrode tip. The top of the piston was black with carbon deposits from what I could see through the spark plug hole. I think my wife is lugging the engine too much, but she says that she is not.

I put a new plug (NGK CR8E, same as what was in it) in. I also put the fuel screw back to 2 turns, and took the airbox cover off, thinking that I had a rich condition. It cranked easily, but the bike had been sitting in a warmed work area. This morning after sitting outside in the cold overnight, it was difficult to crank. It would sputter and try to start with the throttle closed. If I tried to crack the throttle, it would not even sputter. After a few tries and then letting it sit for a few minutes, it cranked and stayed running without opening the throttle at all.

So, what i am seeing is that at 3 turns out on the fuel screw, it will start up and stay running easier with a bit of throttle. At 2 turns out, it will crank up and run without throttle (adding throttle makes it worse), it just needs several tries and a few minutes break in between.

Idle is being set at 1250 to 1350 RPM. At 2 turns out, the idle knob has to be adjusted down a bit. At 3 turns out, the idle has to be adjusted up a bit. At 3 turns out, it is difficult to keep idle set and it is not smooth. If I let it drop below 1250, the engine wants to stall.

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Further update.

I picked up the new battery today from the dealer. They kept it for a day to charge it up for me on their charger. After install, the motor turns so much faster now when starting. I think this is going to help big time.

While I was there, I also asked the parts guy about my problem and told him about the carbon build up on the piston and plug. He has been around this stuff for a long time. In his opinion, the fouling carbon may be building up because the bike is lean and that the choke is staying on a long time causing the build-up. He said to try a shim/washer to raise the needle. He says he thinks the extra richness would also help it start easier.

I am going to leave everything as-is for now, unless Eddie suggests something. I have the fuel screw at 2 turns out, airbox cover off, new battery, new spark plug (gapped per factory spec at 0.029). I'll see how it starts tomorrow morning. The battery may just do the trick, I hope.

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the needle straight diameter is very lean on the stock needle.

shimming wont help that.

sounds like you need to set the fuel screw at 2.5 turns and just keep the bike running with the throttle during warm up.

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the needle straight diameter is very lean on the stock needle.

shimming wont help that.

sounds like you need to set the fuel screw at 2.5 turns and just keep the bike running with the throttle during warm up.

Eddie, thanks so much.

I rode the bike around today with the airbox lid off. It is too loud.:worthy: It also slightly hesitated at mid-rpm, full throttle. It does not do that with the lid on. I am going to put it back on. I am going to leave the fuel screw at 2 turns out and see what happens tomorrow morning since I have the new battery now. It is spinning the motor so fast now that it has to make a difference. If it is still giving me trouble even with the new battery, I will do the 2.5 turns and hold the throttle open a bit. I agree that should do it. After a few weeks of testing in different conditions, I'll report back if that is the solution for sure.

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