Hey Guys. New to the forum. Have an 07 kx250f. Bought it a couple of weeks ago and having a problem with poping thru the exhaust. Brought the bike home from the dealer and pop pop pop. brought it back and they said it was the gas they put in it was seperating (ethanol crap). so they pulled the carb and cleaned it up. I had drained the gas tank and filled with shell premium 93 octane with fuel stabilizer to keep it from seperating. it ran pretty good with only the occasional pop but now its coming back. I pulled the plug and its clean.Question: has anyone else run into this problem? can I use a gumout to clean up the system ( the fuel couldnt have seperated this quick so some crap must have been hiding in the fuel system somewhere) or will gumout make it worse? I'd hate to go thru the hassle of pulling the carb if I dont have to.what brand of gas has everyone found to be the best? has anyone had any success with an octane booster and if so which one or is there some other secret to boosting the octane? on another note anyone here from Massachusetts? I live north of Boston (Tewksbury area)and looking for some pits to ride in, any ideas? other than that the bike is the *****. what a blast it is riding this machine. have an old suxuki pe250 and thought that was fun but this bike blows it away. nice power for a four stroke. I heard they're coming out with fuel injection for the 08 450, any chance they're going to do that for the 250? anyway thanks fo any help thats given.

Paul

 

I can't answer your questions about the bike but I use this stuff in my truck & yahama 4 stroke boat motor. Definately made my boat start easier.


http://www.seafoamsales.com/products.htm

 

are you shure its not backfiring? i had a crappy chineese knock off for awahile and it had the same sort of problem, when i let off the gas every once and a while it would go brapppp and it got more and more frequent... until the exhaust fell off. when i put it on i used some small lock washers and it never happend again. you should check the spark arrestor to.

 

Vlodpg, thanks for the tip on the seafoam.Have you used it in the crankcase as well as the gas? Slaughter King, yes I do think it's backfiring, thru the exhaust which would indicate a problem with the carb.checked the exhaust and it's tight. I drained the gas tank andthe carb bowl and flushed with some gumout. When I reassembled everything and start her up she runs a bit better but it's not completely gone. Do you guys get any poping or snapping at all when you let off the throttle or is it just me? The manual says it's a 13.5 to 1 compression ratio so I can see where some crap in the gas would affect it and a poor grade of gas would also do it. When you buy high test gas they could be selling you anything, who knows if it's really 93 octane or not. What brand gas do you guys use, Shell, Mobil, Texaco or something else? Does anyone sell gas without ethanol anymore? Does anyone use octane boost and have you had luck with it? The bike has less than 5 hours on it and I didnt beat on it so I dont think it could be anything mechanical, also it doesnt do it when powering up only when you close the throttle and brake with the engine. The plug is clean and tan so the air/fuel mix looks good. Maybe I'll try the pilot screw, anyone buy the "Pilot screw adjuster" ? It looks kind of tight to get anything else in there, who the hell designed that? Thanks for the help.


Paul

 

Not sure if this helps but my 06 kx250f has a slight back fire when the air is cold or dense. Check your jetting for your climate. I haven't heard any problems about the 07's yet.

have 85hrs on mine (mx) with no problems kx250f's kick ****!

 

I have some decel popping if I'm in the right gear and there is enough back pressure while going down a hill. All I do is touch the throttle and it goes away. It might be that your jetting is a little off. Maybe the air mix screw worked out a little. Oh and welcome to the site. Nice bike.

 

Hey Guy's thanks for the tip's. Found the problem to be the pilot air screw adjustment. Got it to stop after a few setting adjustments but then had a problem with the srew falling out. Bought a aftermarket screw that extends out of the carb for easy adjustment and it's fixed now. Love the bike it's a blast, took it out in the snow a couple of times, getting the itch for spring real bad.

 

Awesome Paul, its great to get things figured out.

 

i need to learn more about carbs... spend so many years with EFI i'm a little clueless when it comes to my bike.