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Discussion Starter · #1 ·
Working on an 02 trailblazer 250 2x4 with carb/intake problems. Here's the scenario:
Bike starts and idles(a little rough) without the airbox lid, air filter or entire airbox off or my hand partially cupped over the intake part of the airbox when the box is still attached. Once I give it throttle-when it hits "midrange" it starts to bog like it's sucking air bad. At idle, if I install the air filter, it bogs to the point of stalling out. if you pull the choke knob when it's idling, it kills it. cleaned the float bowl & pilot jet-soaked for 3 hours. Also tried spraying starting fluid at intake manifold, thinking there might be a crack, but no change in idle speed. Turned air mixture screw in all the way than 1/4 back & it ran a LITTLE better, even went down to an 1/8 turn out & still bogs. I'm stumped!
 

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have you checked the spark plug and gap?
 

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Welcome to the boards!:arco:
 

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sounds like its too rich. if the choke kills it right away, then that says to me that it is really rich. also, if it idles with the airbox lid off, means its getting a lot more air, which means your getting a better air/fuel mixture. once you put the lid back on, it restricts the available air, the fuel/air mixture goes way to rich side and it doesnt want to run.

to me, it sounds like you will need to change the jets in the carb and go leaner.
 

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Discussion Starter · #5 ·
r.e. 250 trailblazer carb problem

Checked the spark plug, because I didn't have another one, I cleaned off all the yucky carbon black crap with a wire brush & gapped it to .028(?) read that somewhere. Would running rich bog it down like sucking air? It just sounds like it grabbing a fistful of air? Same sound-exact opposite problem?
 

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carb

sounds like its too rich. if the choke kills it right away, then that says to me that it is really rich. also, if it idles with the airbox lid off, means its getting a lot more air, which means your getting a better air/fuel mixture. once you put the lid back on, it restricts the available air, the fuel/air mixture goes way to rich side and it doesnt want to run.

to me, it sounds like you will need to change the jets in the carb and go leaner.
X2...too rich, especially since you "cleaned all the yucky carbon stuff off the plug."

lean out the jetting in carb...
primary jet = idling & low end,
needle jet = mid range,
main jet = top end.

Drop down a jet size or drop the needle down a notch or two.
 

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fouling the plug........running too rich.
 
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