08 CRF250 dies from full throttle at idle

Hey all, new to the site. Glad to be a member.

Just got an 08 CRF250 and was told by the owner it needed the valve clearances checked. The bike is very easy to start when cold. I checked them anyway and found the the intake clearanes at 0.04mm left and 0.08mm right. Exhaust was pretty good. I went ahead and shimmed all 4 valves and are now in spec.

My problem is when the bike is idling and I twist to full throttle quickly it chokes and goes to stall. If I give quick 1/4 throttle blips it is very responsive and crisp.

Im thinking it is most likely carb related, but am not very experienced with bikes and would like some advice on where to start.

Thanks in advance.

the 08's run lean and thats why it boggs, jetting change and carb clean and it will be good. however dont expect the vavles to stay inspec once they have moved once - they just keep moving expect to be replacing the intake valves soon

Thanks for the reply. I just took it for a quick spin and while riding I can give full throttle, it just hesitates for a millisec then pulls nice. I thought it would be running a tad rich? Still need to check the plug to verify.

What's involved with valve replacements? Do I have to do all, or can intakes only be done?


That bog, or hesitation, on quick throttle opening is definitely a jetting issue. Check & adjust your fuel screw, go to a larger pilot jet, or go to a smaller leak jet in the AP-or some combination of all three. If the bike runs really well everywhere else except the hesitation on quick throttle opening, I would start by changing out the leak jet to a smaller one. Try a 55 or 60 leak jet. However, if the bike is not running perfectly everywhere else, then you may need to adjust the fuel screw, and or change the pilot jet, or needle position. I would start by cleaning the carb, putting in a rebuild kit, setting your floats to the correct level, and then changing out the leak jet.

Edited by Kawabuggy

I would just get a JD jetting kit, the FCR is an annoying carb to work on, the less times you have to remove it the better:



Pull the carb out, inspect the condition of everything, make sure nothing is clogged, and put it back together with the kit and you should be really close. Pay particular attention to the accelerator pump, it sounds like that might be related to your problem.


Make sure you have a clean air filter, new spark plug, and valves are in spec, and the bike should run well.


I have heard the slide on the FCR can leak causing funny jetting issues, i've never had it happen personally but something else to check while you have it apart.

Thanks for the info guys, much appreciated. The bike runs fine all through the rev range, apart from the hesitation. Will definately check out the carb.

07,08,09 were known for that slight bog when you open the throttle look at reviews for the 09 or 08 from the big mags some of them have jetting recomendations.. yes you can replace intake valves but make sure you get the seats cut!, also put stainless valves in with the appropriate springs and they will last for ages.

Ok kool thanks mate.

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