2005 Ninja 250 idles but bogs down after throttle

[enkhamar]

Hey guys, new member here. I just recently purchased a used 250 from a local friend and have been riding it around for about a month. I had issues with the bike hanging at 3-4k RPMs before idling back at 1k. So i figured I would clean the carburetor. Ironically, I had cleaned the carburetor on a 150cc moped before and thought it would be similar. I was wrong. So essentially after a ton of messing around with the idle screw mixture, accidentally adjusting the carb sync screw to god knows what and back to equal levels of tilt for both carbs, im left at a loss of words.

The problem with the bike is that when warmed up via choke, it will idle. But the minute that I add throttle it will start bogging down. However if I add throttle slowly, it will climb up to maybe around 5-6k rpms before bogging down. My friend found that if we stuck our fingers in the airbox and restricted the amount of air going in, it would rev up just fine. We have tried even unscrewing the idle mixture jet 3 turns and 2 1/2 turns out and it still bogs.

Any ideas?

[Racer x]

Welcome
It sounds like you need to replace your pilot jets.

[enkhamar]

I went out and purchased pilot jets and replaced them, however I am still having the same problem. When I pulled out the spark plugs I noticed there was oil around (not on the tip) the spark plug. I may have overfilled the oil, could this be causig the issue? sorry guys im a newbie around here, just started riding motorcycle after upgrading from a 125cc moped about 4 weeks ago

[jkv45]

It's possible the slides may not be rising properly. The diaphragms could be installed incorrectly or they may be damaged.

Did you pull out the main jets and clean them internally? Did you remove the idle mixture caps and clean the passages? Did the idle mixture screws have a washer and an o-ring on them?

[enkhamar]

I did remove all the jets inside and let them soak in carb cleaner (gum-out), the diaphragms appear to be installed correctly/undamaged. I was unable to remove one of the idle mixture screws due to it being stripped however Im not sure that may be the problem as it was running beforehand without me touching it.

[DaBlue1]

Originally Posted by enkhamar

.... I had issues with the bike hanging at 3-4k RPMs before idling back at 1k.

The problem with the bike is that when warmed up via choke, it will idle. But the minute that I add throttle it will start bogging down. However if I add throttle slowly, it will climb up to maybe around 5-6k rpms before bogging down. My friend found that if we stuck our fingers in the airbox and restricted the amount of air going in, it would rev up just fine. We have tried even unscrewing the idle mixture jet 3 turns and 2 1/2 turns out and it still bogs.

Any ideas?

First thing is...if it hangs at all, it's running a little lean
Second, your idle speed is too low, it should be adjusted after the bike is completely warmed to 1300-1400 rpms. You can't whack the throttle open on these carbs when the bike is cold. It takes a little time to get the engine warmed up. Easing the throttle open works best.

If you have to restrict airflow to make the bike run, your probably getting too much in the first place, check for leaks around the carb boots.

Since you had the carbs out, did you notice what size main jets it had in it?
Any other intake/ exhaust modifications on the bike?
What was the condition of your air filter?
How old are the spark plugs?
When was the last valve adjustment?
How much oil did you put in the bike? Have you corrected the level yet?

[jkv45]

Originally Posted by enkhamar

I did remove all the jets inside and let them soak in carb cleaner (gum-out), the diaphragms appear to be installed correctly/undamaged. I was unable to remove one of the idle mixture screws due to it being stripped however Im not sure that may be the problem as it was running beforehand without me touching it.

Did you take a small copper wire and run it through the main jet? There can be deposits stuck to the inside of the jet that soaking won't remove, and spinning the jet around a copper wire while spraying with carb cleaner will guarantee they are completely clean.

Something is restricting the flow of fuel as the RPMs increase or possibly the slides are not lifting correctly.

[enkhamar]

There is no history of a valve adjustment ever taking place in the bike's 9k life. I have taken a small guitar string and run it through the jets. I am considering buying larger jets to correct the issue. There are no performance or cosmetic modifications on the bike, it is stock. I will be correcting the oil level today, and i believe it was past the full line on the gauge. I washed the air filter and it is now spotless. I did not notice the size of the current jets, but they should be stock. I will remove the carb again today and double check.

Is it possible that a valve adjustment is needed/could be causing this?

Thanks guys for all your input

[DaBlue1]

Originally Posted by enkhamar

....There is no history of a valve adjustment ever taking place in the bike's 9k life.
....Is it possible that a valve adjustment is needed/could be causing this?

A hanging or hunting idle can be a sign that the valves are out of adjustment.
Valves should be adjusted every 6k miles. First make sure your idle speed is set correctly.

[Alex]

/thread moved to pre-gen tech