Carb issues?

[Citykid]

2011 ninja 250. When I got this bike the air box had been removed and there was no filter. Obviously a problem but the bike ran and was cheap. I put a k&n pod on it and suddenly it won't hardly run. So with no filter I can see air/fuel blowing out the no1 carb. Checked timing, valve clearance, and did leak down and all were good. Pipe is stock. When bike is idling I can see the slides fluttering and sometimes when I open the throttle they just continue to sit there and flutter. I cleaned the carbs and put 40 pilot and 110 main jets. Still same condition. Going to go back to stock jetting. 38 pilot and 98 main w/ fuel screw 3 turns out. Spark plugs are black but I can't figure out how it can possibly be too rich. I'm truly stumped. Please help.

[Citykid]

So finally found a video of what my carb is doing.

http://www.youtube.com/watch?v=N9a4h9zSODc

Exhaust valves are all .009" and intake valves are all .007"

Leak Down test showed 2% leakage.

Is this an engine problem or carb? Seems like the carb is over pressurizing the bowl and blowing fuel out the carb intake.

I guess I'll keep trying things until I find a solution. All ideas are welcome as I am running out of things to try.

[Hero Danny]

Seems odd, the fact that the K&N pods made it worse tells me your jetting is all wrong. Find a stock airbox and play around with the jetting.

[jkv45]

Check the float levels. Check the carb diaphragms for damage.

Turn the idle mixture screw to 2 1/2 turns in as a base and sync the carbs.

I'm not a big fan of pod filters myself.

[DaBlue1]

Originally Posted by Citykid

So finally found a video of what my carb is doing.

http://www.youtube.com/watch?v=N9a4h9zSODc

Exhaust valves are all .009" and intake valves are all .007"

Leak Down test showed 2% leakage.

Is this an engine problem or carb? Seems like the carb is over pressurizing the bowl and blowing fuel out the carb intake.

I guess I'll keep trying things until I find a solution. All ideas are welcome as I am running out of things to try.

Reversion is the flow of the air fuel mixture out of the cylinder and into back into the intake manifold. Reversion happens even on a stock engine because the piston is moving up the cylinder before the intake valve closes. This is usually a sign of a needed valve adjustment or the timing is off.

https://www.youtube.com/watch?v=VLLZavItixY

The fact that you're missing the airbox may be a clue that the PO did something to the engine. (maybe have advanced the timing using a offset key). It's also possible your timing could be changed throughout the rev range, however at idle speed the result is carb spitting or reversion.

[csmith12]

Welcome John!