03' cr250 strange WOT bog?

Hi everyone,


So my uncle and i go to the track to ride ( first time on my new bike) so riding around the track my bike seem'd to be all good (i ddn't really open it up im guessing) so we go across this road to a super mine dump so my uncle can try get to the top he makes it 3/4 way up so i said to him try my bike out because his was running poorly on that day, so he gets a good run up to the hill then ass soon as he is WOT bike starts bogging or missfiring strange noise never heard it before but it was only at continuous WOT, the bike ran fine after that the rest of the day could it be a jetting issue? to lean starving for fuel? i would like some guide lines on this kind of problem so i can try fix it up myself ( broke after buying the bike) :D any help would be greatly appreciated thanx guys :D 



Do you know what jets are currently in the bike? The main jet controls 3/4 to wide open throttle and a bog usually means lean and sputtering is rich. If it still has factory jetting and you were riding on a hot day then chances are your probably running rich. Did you attempt to run it wide open throttle anymore after that? Sometimes if your jetting is a bit rich and your just putting around for awhile the engine will load up and need cleared out. Best way to clear it out is by simply hammering down on it to burn up all that fuel. Chances are if its to rich doing this will cause it to foul the plug. If your just learning to ride or spend most of your time riding slow then you can get away with a bit leaner jetting to help keep the bike from loading up. If you are still running the stock carburetor then you are going to need to get very familiar with jetting and how to successfully determine what changes need to be made and how to make them. If you are able to give us a run down on what pilot jet, main jet, and needle and clip position then we can give you a good baseline to go off of. Oh and your elevation and temperature as well. While you have the carb apart clean every single passageway that you can access and then blow out with compressed air afterwards. Make sure to have a clean bike before you start taking things apart and go slow. Having a service manual is also a must not an option. You can download one for your bike from tradebit.com for pretty cheap.

Hi man,


thanx for your input on subject i checked out my carb today i am running a 400 main and a 30 pilot my elevation is 1753 meters and we ride in temperatures between 20 - 30 degrees celsius and that day we went was rather hot but, the next day i went to a place called maraisburg and opened the bike up there it also like skipped a few strokes if you can call it that yea i sprayed the whole carb down with carb cleaner made sure all the passages were clear i have yet to test the bike though and i downloaded a manual, i got the bike second hand so he obviously didnt have the manual /: thank you again (:

If it is a top end bog it can be caused by a couple things.  broken reeds, too lean of jetting, or lack of compression (worn out piston/rings).  If the bike is "skipping" that can be an issue of rich jetting.  i have seen a blown flywheel side crank seal cause "skipping" in the top end too. 

Pull the plug, tell us what color it is. Second, get a compression tester and do a compression test. Report back. 

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