'03 250 Exc

[Creeper9]

Hi. I have an '03 250 exc and I have a question I hope you guys could help me with. I have a slight hesitation right off idle in my bike when give it WOT. I think it's a lean bog, but I'm not quite sure. The jetting on the bike is stock, and I ride at sea level. sunocco pump 94 with spectro ar 40:1.

I know this is going to look stupid, but if you sound it out it's like buhwaaaaaaaaaaaaaaaaaaaaaaaah. The hesitation is slight, but detectable. It does it from dead start holeshots, and roll on holeshots. Is this the A/S? or pilot doing this to me? Is it a lean bog?

Sorry for the strange nature of the post, but I'm rather new at jetting, so any help would be appreciated.

Thanks
-Kurt

 

[RABEXC450]

I am having the same problem on my '03 450 EXC, my business partners (same bike) doesn't have the problem. We got them from the same dealership at the same time.

I am interested to see if anyone else has this problem.

 

[Creeper9]

That's interesting. I have a friend also who has the exact bike as me who does not have this problem. His feels much stronger off the bottom than mine, and has NO hesitation. The carb settings between the two are identical. I checked. He runs his mix the same as mine too. It's weird. :think:

 

[Fred T]

Kurt
Try this:
45 pilot
N3CH #2
178 main
A/S around 1.25 to 1.5 out.

 

[Boozer]

if the engine bogs, dies or hesitates when the throttle is wacked open from low engine speed, then it is a accellerator pump issue. That is it's purpose, to compensate for the sudden lean mixture when the slide opens quickly. I'm guessing the pump is not supplying enough fuel or that the timing of the pump is off. What model Keihin do the 250F's use? if it is the same as the WR/YZF250s (37mm), then the fuel is controlled via leak jets. Use a smaller leak jet to supply more fuel to the engine.

Trying to fix the bog with jetting is not the correct way to do it. It may fix the problem, but the engine will run excessivly rich, robbing performance.

 

[Boozer]

oh no, just realised we were talking two smokes! should have guessed from the bbbwhaaaaaa! i was thinking of 03 250EXC RFS! forget i just posted. forget.... forget....

 

[RABEXC450]

I'm having the exact same problem; however with a four stroke. In the same boat as I have a riding partner that ha the exact same bike with more throttle response without the hesitation.

R

 

[Creeper9]

Thanks Fred!!

I'll try it out this weekend

 

[Humai]

Creeper, check the float level as well - an unusually low float level could possibly cause the problem.