KLX250s Surging at WOT
 

Hello everyone---------I purchased a 06 KLX250S yesterday======I bought it from a local dealer who wouldnt let me ride it out of the parking lot=====cause I only have a learners permit (endorsement)==he said it was due to insurance====anyways===today I rode it for the first time and I notice that at wide open throttle===the bike surges pretty bad-----I have no idea where to start=====the airbox lid is missing and thats the only mod I can see done to this bike------I can tell the carb HAS been off before because I had to loosen the clamp and push the carb on the rest of the way===which made no difference with the WOT surge=====do I have old fuel? are the valves out of adjustment(bike has 9000 miles) though I dont hear any valve noise AT ALL when its idling=====is it simply a dirty carb? anyone experience this before? and where do I start? I am a complete NOOB to the KLX===I am a professional auto mechanic===so I can do anything that needs to be done=====I really think the jetting has been messed with====but why would someone mess with jetting and leave the exhaust stock=====last question===what size spark plug socket do I need====5/8" automotive===or is it a smaller size one like my GSXR

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the bike runs smooth and great===under 3/4 throttle
idles fines===you have to use choke when its cold-----I've put 8 miles on the bike so far----------did I even get the bike warm enough?---I rode up and down my side street about ten times===also what is the redline of these bikes====I've read 8500rpm but not sure if they were refering to a KLX250s or not=====thanks for the help guys

I'm guessing with the surge problem it may be a lean condition but in regards to that, did the bike come with a 30 day warranty etc from the dealer? It might be just worth a shot giving them a call and seeing whether they would fix it for you as they wouldn't let you test it.

Its a 2 hour drive to get to the dealer====I'd rather fix it myself since I am a auto mechanic======its my nature to FIX IT myself :) I agree its a lean surge===I got to ride in 1st gear at was able to do a few good 1st gear pulls and I didnt feel it====and of course as soon as I hit 2nd gear today I felt it LOL

well if you thinks it's a lean condition it might pay to either put a lid back on the airbox (if you can access one) and see if it plays up or otherwise pull the carb off and have a look at the jetting on it because if you thinking it's been off then it could have been messed with.

Sounds lean to me. This bike likes lots of fuel above 5000K, and WOT.
Drop in a #132 main jet to help her get up. :D

I am almost positive its a carb issue now======I just realized====the bike is from arizona(has arizona plates) which is a desert====or for you aussie's :) its as hot as the outback in the summer (arizona is)===I live in washington state ------which is a cool climate=======if the bike is or was re-jetted to deal with the arizona heat======wouldnt it then be lean up here in cool washingtion?=====I am going to take the carb off in the next day or two and make sure theres no crap in the carb and see if I can see what MAIN jet is installed=-=-====that will tell all=====i just tried to remove my spark plug with the tool that came with the bike=====and by the time the spark plug is unscrewed the tool is hitting the gas tank and I cant wiggle the stupid thing out of there=====I wanted to verify the plug wasnt cracked our maybe get a read on the fuel mixture by looking at the plug====but I failed that mission and put it back together before I broke something====I'll bring a special wobbly socket from work====

Does it still have the stock exhaust? Sounds like the previous owner may have been running an aftermarket exhaust, then returned the bike as close to stock as possible when he/she traded it in. The lid may have been thrown away.

Unless you have the Australian model, the stock exhaust is too restrictive to accomodate a fully open airbox with carb at WOT, no matter what jetting you have. A lot of times you will get what feels like a lean surge, but it's actually due to excessive back pressure.

good call man========thats another thing I was thinking=====that he took his expensive exhaust with him with the bike was trade..................I'll know for sure after I pull the carb and verify its clean and at least has a main jet that is useable============

On the valves........they close up with use rather than loosen up, so you won't hear extra noise. Check the intake valve clearance. This isn't likely your problem as it would show up when trying to start the bike.

My guess is the carb. Normally, the high speed circuit doesn't get clogged with crud, but the pilot circuit (idle) does. Even with a larger main jet, the needle will restrict fuel flow. Stock, they come set at the lean side for emission reasons.

Ride on
Brewster