Hi, WR250F 2005 bogging down at low rpm a little.....

Hi, I have a WR250F 2005 steel frame that i have been using issue free for the past 2 years but i have developed a slight issue.


Gradually the bike hesitates for about half a second at low rpm in all gears. If i am stood up on the pegs and the bike bogs down in can nearly throw me over the handle bars head first. The bogging down is at its worst when i start the bike from cold but the bogging down happens a bit less when the bike warm, but even when the bikes up to temperature it still bogs down a little bit.


The issue has been getting gradually worse over he past 500 miles.


Another point to note is that the bike is also back fireing more and more as i role off the throttle, so my thoughts are that it may be running a liitle rich, would my thinking be correct? How can i adjust the fuel to air ratio? that the bikes using.


The bike had oil, oil filter, air filter changes every 300 miles and valve clearance check every 1000 miles. The valve clearances were all in tolerance about 700 miles ago and i have not had to adjust them in the 300 miles i have owned the bike. The bike starts fine with the choke on and runs fine other that the slight bogging issue.


 I bought the bike with unknown mileage have personally done roughly 4000 miles green laning at an average speed of 20/30mph. So 4000 miles at an average of 25 mph would me the engine has done 160 hours with just basic servicing and valve checks ect.. which i am quite pleased with.


Sorry for sounding a bit simple


Any help is much appreciated 


A few snaps of my bike when clean




a few snaps when not so clean




In the lake district









do some reading on this forum using "bog" as search word. Read others descriptions of their symptoms and see if that is what you're experiencing.

If you haven't changed anything on the bike and the 'issue' just started and is getting worse, I'd say it's maintenance related.

I'd start with cleaning the carb and air filter.

After a few more days searching for a possible resolution. Could it be that i need to adjust the fuel screw thats located underneath the carb? I believe some people fit an aftermarket fuel screw to make adjustment easier.


Would it be clockwise or to increase fuel or reduce it? 

Clockwise to decrease fuel.

Has the carb ever been cleaned? I took mine off a while back to check the pilot jet and it had dirt in the float bowl. The pilot jet can get gummed up over time from todays crappy gas. I'd start with cleaning the carb and replacing the pilot jet and put an adjustable fuel screw in while you're at it.

For some unknown reason my carb had a 50 pj which was 3 sizes too big! With a 42 installed and the fuel screw adjusted, I can creep along at idle and a snap of throttle lofts the front at low rpm's. Much better!

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