Lean Condition Causing Bike to Bog Down?

[Hatter]

So long story short, my 2009 ninja 250 idles great but dies if I hit the throttle quick. If I slowly turn the throttle it usually makes it up to 4k rpm where it hesitates and bogs down. Occasionally it breaks past 4k and revs up. Backfires sometimes on deceleration.

I took off the carb and clean it out. Although it was basically spotless already. Both main jets and the passages were 100% clear. The pilot jets were a tad dirty. Floats appeared to be fine (still have to measure).

Now the PO had installed a slip on exhaust but didn't jet it. So I'm wondering, would that exhaust in combination with the already lean factory setup, result in the problems I'm having because it's running super lean? I'm going to take out the plugs today and look at them.

Will a lean running bike result in bogging down and/or dying when the throttle is hit?

[DmbShn41]

Going off what I know and have learned here so far. If you swap out of the stock can, and or header assembly, you are opening up the 'airway' as the stock assembly creates a certain amount of back pressure needed with the stock setup, presumably for it to meet the EPA standards at time of sale.

Based on what you describe, it is lean. If carb is clean as you described, you need to jet it and set the carbs properly to the current setup. Checking plugs prior to, cleaning them, then checking afterwards can help indicate the condition. There are plenty of DIY's here plus a plethora of info. Utilize the search feature to your hearts content. The DIY is linked off Tech forum main page.

[Motofool]

Originally Posted by Hatter

.......... Will a lean running bike result in bogging down and/or dying when the throttle is hit?

Yes; too much cold air suddenly cools the combustion down to the point of extinguish it.

Link to original page on YouTube.

[DaBlue1]

Don't whack on the throttle when the bike is cold. Use the choke when starting the bike until it's warm.

It may not be actual backfire, but exhaust popping which is somewhat normal for a slip on exhaust. One reason you hear it (popping) so well is because you have an empty tin can instead of a heavily baffled steel drum (stock exhaust).

The popping noise can be reduced by doing the kleen air delete mod, which stops the extra air entering into the already lean and hot exhaust.

Most people who have installed the M4 and Dan Moto slip on exhaust have also shimmed the needles and removed the snorkel and kleen air system.

Also the popping that you hear on decel comes when you quickly and completely close the throttle (from WOT), doing so causes a lean condition. Ease the throttle closed.

[Hatter]

I use the choke until the bike is warm, but I still experience the same thing.

So a lean condition could, in theory, result in the issues I'm experiencing? I just hate to spend $75 on jets, only to find out that's not the issue

[csmith12]

Originally Posted by Hatter

I use the choke until the bike is warm, but I still experience the same thing.

So a lean condition could, in theory, result in the issues I'm experiencing? I just hate to spend $75 on jets, only to find out that's not the issue

http://www.jetsrus.com/ much, much cheaper.

[Hatter]

Originally Posted by csmith12

http://www.jetsrus.com/ much, much cheaper.

I was actually thinking of just getting this kit: http://goo.gl/J2Vu4e , but that site may end up being even cheaper!

I was including the cost of a K&N pod filter. I figured I might as well since I have everything off already.

Would you say increasing the main jet size to 102 and pilot to 40 to be adequate? I'm a bit confused on the size I should get, from what I'm reading people with similar setup ups add #100-#110. Is it just trial and error? Are the needle shims a hardware store item?

https://www.ninjette.org/forums/show...t=10208&page=2

EDIT: I just ordered #112, #110, and #108 with #40 Pilot. I figured one of those will work. I also purchased a K&N 0990 filter.

[DaBlue1]

Originally Posted by Hatter

.... I just ordered #112, #110, and #108 with #40 Pilot. I figured one of those will work. I also purchased a K&N 0990 filter.

Have a look at this thread also. https://www.ninjette.org/forums/showthread.php?t=124144

[ninja250r81]

Will a lean running bike result in bogging down and/or dying when the throttle is hit?

Lean - when the bike is not at operating temp "low revs"
rich - when the bike is at operating temp "high revs"

Yoshi slipon, k&n filter, no snorkel

Dynojet stage 2 jet kit using the supplied needles with 098 jets and everything else set as factory at 650mtrs above sea level.

Start's better when the choke is on 1/2 choke needed.

It's a little rich, but that's what i wanted going down to sea level within 150kms from home to account for the extra air.

MOTOFOOL nice video

[Hatter]

Originally Posted by ninja250r81

Will a lean running bike result in bogging down and/or dying when the throttle is hit?

Lean - when the bike is not at operating temp "low revs"
rich - when the bike is at operating temp "high revs"

Yoshi slipon, k&n filter, no snorkel

Dynojet stage 2 jet kit using the supplied needles with 098 jets and everything else set as factory at 650mtrs above sea level.

Start's better when the choke is on 1/2 choke needed.

It's a little rich, but that's what i wanted going down to sea level within 150kms from home to account for the extra air.

MOTOFOOL nice video

I'm only about 180m above sea level. so #108-#112 is probably a bit too much. Sounds like #100-#102 would have been a better choice.

[ninja250r81]

Mine is dyno tuned, sorry i missed typing that bit of information.

EVERYBIKE is DIFFERENT so buy a wideband o2 sensor and gauge and have a go at diy.

You might be surprised that you may need different settings on either side of the carb "sync"

[Motofool]

Originally Posted by Hatter

I'm only about 180m above sea level. so #108-#112 is probably a bit too much. Sounds like #100-#102 would have been a better choice.

Before starting that long and painful process of jet-testing, consider that other things should be in order for a proper carburetor's tuning, such as fuel level in the bowls (float's height), non-leaking boots (no air intrusion), plumbing of the fuel (including venting of the tank and internal fuel filters), spark plug's gaps, air filter cleanness and valve's clearances.

Please, take a look at these:

http://faq.ninja250.org/wiki/I_want_...uretor_jetting

http://faq.ninja250.org/wiki/Removin...re_screw_plugs

http://faq.ninja250.org/wiki/How_do_...n_the_carbs%3F

http://faq.ninja250.org/wiki/How_do_...n_the_carbs%3F