03 RM bogging at mid-high revs

[Light_Rider]

I purchased a 03 rm 250 last summer and thought i could fix the problem of it bogging out at mid-high revs, i was wrong any help would be greatly appreciated!

Alredy cleaned carb ,rebuilt top end , new stator coils, good gas, dont know what else to do.

[the_privateer]

whats the spark plug look like?
I'm guessing it is black and kinda wet

first set your float
if it still bogs
try raising the clip on the jet needle to fix the mid-range
go to a smaller main jet for the high-rpm bogging

keep watching your sparkplug, if it comes out white you have gone too lean, it should be a tannish mocha color

[eb77k]

I'm thinking jetting or carb adjustments, from your posts that's all that's left.

[Light_Rider]

Thanks for the imput ill try that right now

[DR-Z125L]

imput?...............nah im just messin

[BodaciousNick]

yeah, carb tunning/jets. Look for a maintenance book for you bike...always a good investment. you can practically build a bike from my Clymer manual. best of luck. thats an awesome bike!

[Light_Rider]

before i buy a new main jet woudnt it run good on factory settings?

because its at factory and im thinking its not the carb because i ajusted the clip on the jet needle and didnt see too much improvement.

[the_privateer]

from the factory, bikes are jetted for sea level, and usually safely rich. its not very likely a bike will come jetted perfectly from the factory-there is usually much to gain in properly jetting even a stock bike

there are so many factors that effect your jetting that it makes it a big suspect for your bogging, especially considering what you already replaced-top end, stator coil -and i assume since you did those you also have a clean air filter and correct sparkplug

at this point, if it were my bike, i would return the clip and ride it around using only half throttle, if it runs good and doesn't foul the plug, leave the jet needle alone (now i'm guessing the bog is more in the higher revs, if not let me know). Is the sparkplug black, wet, or sooty? do you have spooge coming out the silencer? if so, the bike is too rich, go down one size at a time on the main jet-they run about 5 bucks each
if the plug is white or looks burnt-that is a lean condition-which can cause bogs but also has a sound you would probably recognize - known as pinging. check your plug-what does it look like?

jetting is very trial and error- do remember though, that a rich bike will only foul plugs, but a lean bike will detonate-which is why i always go down one size jet at a time

[ALLEYCAT50]

I have to jump in here. I have the same bike, and the jetting from factory is way off. Bogging at mid-high reves I assume that means half to full throttle or there about. Do you know what number the main jet is? While you have the carb bowl off check the float height-turn the carb upside down, the floats should stop the flow of fuel when they are parallel to the flat of the carb where the bowl mounts. I think the measurement is 6.5mm(+-1mm).Also check the float jet. But before you do all of this, on the left side of the cylinder there is a dial that is held in place by 2-8mm bolts. This is a pre load for the powervalve. If you back the bolts off the dial should be horizontal when there is no preload on the spring, to a half turn clockwise. Will the bike go in the powerband at all? Here is what my 2003 rm250 is jetted at

pilot jet is a 42, main jet is a 162, stock needle at second clip down. I run 50:1 mix w/motule 800, and I mix my supreme gas(which is only 91 octane here) with 25% race fuel.(so 20 liters of fuel is 15l of super and 5l of race fuel).

Let me know how you make out.

[ALLEYCAT50]

Nice link to setting floats "the privateer" just seen it.

[ALLEYCAT50]

Here is a 2003 rm250 hopup guide that I got my dealer to get for me. They still call for big jets. I tried it and fouled a couple of plugs. Also the power valve setting is half a turn in either direction. Didn't know that......