I recently picked up a 2008 250 as my primary commuter. The previous owner decked it out with all sorts of goodies and sold it to me at a steal.

I was happy with it until I rode a buddy's 2007 250 (all stock), and to my surprize, it felt like it had more power everywhere.

In fact, my bike on the freeway has a hard time even getting to 80mph much less going any faster. But my buddy says his bike will go to 100+ easily, given enough time.


Currently list of mods from intake -> exhaust (from what I can immediately tell):

- Airbox has been completely removed in favor of individual BMC filters for each intake.
- The carb has been fiddled with, as the idle screw caps have been taken out. (I havn't pulled the carb yet. I can imagine the problem is probably with the jets...) However, the stock screws for the float bowl are still in place, and look unscuffed but that doesn't say much.
- Full AreaP exhaust system

I will attempt to pull the main jet and see what it is later next week and report back.

In the meantime, I plan to return the exhaust headers to stock (Thanks Chubbs032!) and use an Akrapovic slipon (noise reasons [neighbors have complained and LEOs have warned...] + got the hookup + can't find a reasonable deal for the stock muffler).


The bike idles fine, warms up fine, but it just feels lackluster throughout the power band. I havn't noticed it being overly hot while running, but I have a mind to pull the sparks to check them for an overly lean or rich condition. Any suggestions or thoughts would be greatly appreciated!

Probably a "stage 2" jet kit with a "stage 3" intake modification. (main jets too small still?)

Also might adjust the shims? Should pull nice mid range at least even with too small jets.

When all is good you should be able to pull up to 95-100mph fairly easily.

Something is definitely not right if it wont get over 80mph...my stock ninja will easily do 90+mph, and I dont have a single performance mod on it.

who was the previous owner? someone on the board?

why not ask him/her what was done? :confused:

who was the previous owner? someone on the board?

why not ask him/her what was done? :confused:

Someone local to me.

I'm in the process of contacting him to see what mods he performed but he's away on business.

What convoluted the issue was really that the bike runs smooth through the revs, idles well, and warms up fine.

It also came with a very large after market rear sprocket (that was for a yamaha...). When I reverted it to stock and the top speed still did not improve much, that is when I got the feeling that something really wasn't quite right.

The bike idles fine, warms up fine, but it just feels lackluster throughout the power band. I havn't noticed it being overly hot while running, but I have a mind to pull the sparks to check them for an overly lean or rich condition. Any suggestions or thoughts would be greatly appreciated!

Based on that, I'd say the bike is jetted too rich. Pulling the plugs will give you a good indication of where you stand jetting wise and I highly suggest it just to eliminate the small chance that you are too lean. A rich bike is okay to ride... a bike that's too lean can lead to a destroyed motor.

If it was a car I would say it sounds like it is running too rich. Pull the plugs if you can and see if they electrodes are black and fouled which is usually a good indicator of running too rich.

Like others are saying probably needs properly jetted/tuned.

I finally got around to pulling the plugs.

http://img697.imageshack.us/img697/8778/sparkside.png


http://img13.imageshack.us/img13/9748/sparktopdown.png


Opinions?

Looks like it's a bit fouled from being rich. Based on the pic, any guidelines/suggestions for how much to lean it out?

TIA

without knowing what's in there now, it's hard to give you recommendations on what you should change.

at least the plugs show it's not running lean, which would be my main concern.

contact the PO and find out what the jetting is or remove the carbs to find out for yourself.

http://faq.ninja250.org/wiki/I_want_to_improve_my_carburetor_jetting

Yah, I was thankful for the non-lean plugs as well.

Thanks for the link.

So it's not as simple & straightforward as going a size or two smaller on the main jet?

it might be... but w/o knowing what's in there now, how will you know what to install? :confused:

some jetting info here...
http://www.ninjette.org/forums/showthread.php?t=10208

it might be... but w/o knowing what's in there now, how will you know what to install? :confused:

some jetting info here...
http://www.ninjette.org/forums/showthread.php?t=10208

Understood. It sounds like a bit of a PITA to do much more than change the main jet so I want to have a plan & basic goal before i start going in there.

This is my primary mode of transportation so I have to try and minimize the downtime.

rejetting IS a PITA.

rejetting IS a PITA.


:(


The bike idles remarkably well, and the sparks arn't too bad, so I am almost wondering if it is too lean when WOT.


Will definately have a better picture if I can get ahold of the PO or when I get the main jets out.. probably tomorrow night.

rejetting IS a PITA.

But a rite of passage for those who chose to enter the dark world of the Ninja right Kelly?

But a rite of passage for those who chose to enter the dark world of the Ninja right Kelly?

some live with stock jetting without problems. for those that like to fiddle with the their bikes or need to rejet (as in this case), getting the jetting to be "perfect" is a time consuming, step by step process.

There are basic jetting specs that will get you in the ballpark, but to get the optimum out of each bike is a trial and error process due to to the inherent differences between bike setup, owner location and riding style.

howdy, Don!
:yo:

I've always thought that my bike being green was the reason I really haven't had any jetting / rideability issues and that's the story I'm sticking with.

Of course being an OldGuy :wheelchair: that little bit of throttle lag gives me time to remember to grip the tank a little tighter and not have the bike leave without me.

Most embarasing when that happens. :focus: