2010 Ninja 250 (Rev limit)

Working on a small bike I picked up in order to build my skills. Did some basic maintenance including rebuilding the carb, new plugs, new coils (used) but still have this problem. When in gear the bikes hits about 8k rpm and won't go any higher. Gear selection changes nothing. If on the stand I can rev it higher, but with a load it stops there. Bike has an aftermarket exhaust. It feels like there is a rev limiter that stops it from going higher. What should I be looking at?

 

Since its a 250 this question might sound silly. Does it feel good up to that point and fall flat or is it just lethargic whole time?

 

8k is about when it transitions to the main jet. The carb needle and main jets would be the first thing to look at.

Stock airbox?
What air filter?
Mainjets?
Needles?

 

The power is 9-12k, theres a fueling problem.

 

Are you sure you are getting enough fuel flow to the bowl?

Stock airbox? Stock Jets? Full exhaust?

For reference, I'm running no air box, with the clamp on K&N filter, Leo full system w/baffle, and DJ 108 main with needle at 3rd clip position. Runs great.

 

Feels good up until that point then falls flat.

 

Stock everything. After disassembling and cleaning, I decided to put it together in stock form. Make sure it's running smoothly, then start tuning. Didnt think the stock jets/needles would make it fall off that badly. I also have some of the pod filters that I will likely move to so I can ditch the stock airbox setup.

 

I figured it was a jets/needles issue but wanted to make sure that I'm not missing something simple prior to starting down that road.

There is also an issue with the dash displaying the speed properly. It will show zero while on the gas. If I roll off and on quickly it will show the speed for a few seconds and go back to zero. I assumed it was unrelated. No change in power when I roll off/on.

 

Is it a stock dash? Stock speedo is cable driven so should be completely unrelated to anything else - pure mechanical setup.

 

Full exhaust, no baffle.

 

Area P setup is a pretty well known full exhaust for jetting. I have never tried it, but I imagine that a full AP with will stock fuel setup will run quite poorly. You need to step up several main jet sizes with that exhaust. Stock main jets are a 98 and I needed to run 110s with an AP

 

Here is the speedo. Assuming not stock since there is no speedo cable. All electrical connection

 

thats aftermarket

 

Yep, no that's a KOSO - requires a magnet setup in rotor or similar for speed I believe.

 

ditch the dead weight

 

Going to pod filters will not necessarily make your bike "breathe" better. That's why you almost never really see superbikes with pod filters anymore. The reason airboxes can actually produce more power is that the air inside is moving more slowly than the surrounding air (with the bike in motion) The slower the air is moving the higher the pressure so the better your cylinders will fill. This is a generality though. Some airboxes on small like on the R3 get modified for better flow into the box but they still have a chamber with some volume that is closed to the outside. I had a couple of 400 Bandits that would hardly even run with pod filters. Had to go back to a stock airbox. Don't even get me going about open velocity stacks or the ones with the screens on them. they may look cool but they don't work.
Oh yeah, check the Koso manual to make sure that your tach is processing the rpm signal correctly.

 

Sounds like my "get it running then work fueling" approach was too far off. At least now I know the carb is functional with the rebuild. Now I'll start tuning

Thanks for the info

 

Not really looking for trying to make the most "power" (it's a 250 ffs ). I just want it to run well so I can turn a shit ton of laps. My thoughts on ditching the airbox are more toward making that area less cluttered. If I can do that and it still runs well I'll consider that a win. If not, I'll keep the stock airbox

So far all of my maintenance that I've done has been general knowledge of mechanic work. Stuff like oil and filter, flushing and servicing the brake systems, rebuild the carb, etc. Now I need to familiarize myself with this particular model and start working on the fueling.

I'll probably keep the speedo though, dont think that's gonna be the deciding weight factor when I tip the scales at 240 right now. That's almost as much as he bike

 

Put the air box back on and de-snorkel it if you must.
If you want to use it as a trainer, consider ditching the Koso and getting some sort of gps based timer/datalogger

 

I've been thinking about the Solo2 lately at the urging of some folks here from another thread I made about a GPS laptimer I bought that is not working. Gonna give it one last go before I ditch it. PZ Racing in Italy is offering to repair it, so I'm going to try that first. It's the MotoD Next that PZ Racing manufactured.