Help with carb tuning issues

[KaTyStew]

Hey there! So I have a 2009 Ninja 250r. Been doing a lot of work on it. Mostly just wanted to get rid of that chrome stock muffler. So I have a classic shorty exhaust (Making it crazy loud which is what I wanted... I'm probably pissing off my neighbors). After that, I removed the air box and replaced it with a K&N pod filter. Obviously needed to rejet the carb afterwards. So I took the carb out the first time, cleaned them, rejetted it to a 102.5, added 2 washers to the needles, and turned in the mixture screws all the way then back out 2.5 turns. Put the carb back in and hooked it all back up just to realize the jets were too big (bike cut off 2 feet down the road). I was able to rejet without having to remove the carb again (which saved some ass pain) and I now have jet size 100. Redid the mixture screws (in all the way, back out 2.5) Still have 2 washers on the needles (I'm thinking this is my problem but please read on so you can tell me if I'm right).

The PROBLEM: So my bike runs, which makes this girl extremely happy! However, Idle speed is too high (between 3000-4000 rpm). I took it for a ride hoping to warm up the engine enough to do what I needed to do with the Idle knob. I brought the idle down to where it needed. It stayed there for about 3 seconds before cutting almost all the way and then picking up to about 6000 rpm. I don't think I'm doing it wrong, but the knob doesn't help bring the idle where it needs to be. I figured riding it would make it go back to normal. But it's still at 3000 rpm. It's pretty annoying and kinda embarrassing sitting at a stoplight with an idle much higher (and louder) than it should be. It also will randomly pick up speed while cruising down the street (keep throttle input the same and RPMs increase around 1500.) I don't know what else to do. Do I drop the needles a little? Did I miss something with installing the pod filter? What should I be checking for as far as hose connections and such? Thanks in advance for all replies and any help y'all can give me.

[Motofool]

Welcome, Kristyn !!!

First, you need to verify that the throttle cables are fully releasing any pressure from the actuator of the butterfly valves.
That way, the regulating screw at the end of the knob can close those valves more in order to reduce the idle speed.
You can gain more slack via the regulators for those cables (to much is not good for fine throttle control).

Second, if you can, try reducing unnecessary noise.
That only aggravates drivers, who can cause us many problems while sharing the roads and streets.

[RacinNinja]

It's lean. Make it richer.

[jkv45]

Sounds like you might have a vacuum leak. Snug down the clamps and check the boots from the carb to the engine for leaks by spraying with something. I like carb cleaner, but be careful not to spray too much or it could mess-up the engine paint. Listen for a change in idle RPMs.

What was the stock jet size? How did you know the Main Jet was too large? With pods I would expect you need to go larger. Search around here to see if there's a good base number to start with. Make sure you are looking at New Gen (08 and later) jetting numbers. New Gens also have asymmetrical carb settings and possibly needles IIRC.

The Main Jet starts controlling the mixture from about 1/4 throttle (in association with the needle) and eventually controls it completely at wide-open throttle (WOT). If it runs well wide-open (after giving the slides time to raise) the Main Jet is correct.

I might remove at least 1 washer from the needle for now. The needle controls mixture in the mid-throttle position mostly.

When working with jetting, think in terms of the position of the throttle (1/8, 1/4, 1/2, 3/4, full) to help you isolate running problems.

Looking at the color of the spark plugs will also help if you get to a point where you're just not sure what's going on.

[CaliGrrl]

Welcome!

[Ghostt]

Paging @ducatiman

[KaTyStew]

Hey ya'll! Thank you for the responses!! I'm getting back to work on it this evening. I'll go ahead and remove one washer from the needle for now... should help more than hinder.

To answer your questions, @jkv45, the stock size for the jets were 98. I have them replaced with 100s. I figured out 98 wouldn't work with my new shorty exhaust because I couldn't get it to red line and it was running way too lean. 100s work well. Bike runs better and goes faster. Only problem is the idle speed.

I'll do what ya'll said about checking for leaks, checking the throttle cable and snugging the clamps and report back with results!

[RacinNinja]

You're lean. Here's a Jetting Database thread: https://www.ninjette.org/forums/show...tting+database

Most running pods are 108-110 Main Jet. Some up size the pilot jet also to correct the idle issue. Factory Pro jets use the same number system as stock Keihins so the numbers are the same.

[InvisiBill]

The jetting database is a good place to start. Then logically step through your fueling to find the optimal configuration. http://factorypro.com/tech/tech_tuni...m_engines.html

[Lazarus]

#40 pilots and bigger mains. ^^ wut they said. My ninja had a k&n filter in the box, no snorkel, and a full exhaust yet I only needed 100 mains and 40 pilots in with 2 washers under each needle. Each engine is different but that's a reference point for you. With pods and a shorty exhaust I would agree with others you may be lean.

[KaTyStew]

I'm double checking the hoses for a leak in it, should I have capped off any hoses with this setup or should I have a few lines that vent to ambient? That seems like the only other line I could have missed.

[Alex]

Is it up and running?

[highvoltj]

My '08 250r started out as a bone-stock 400m bike, essentially brand new.
I too added a slip-on to get rid of the hefty "chrome-can" replaced the restrictive air-box with a K&N pod and went about re-jetting my carbs with a 6Sigma jet-kit...I started by drilling the slides, 2 shims under the needles and added the 40-y pilot and 112.5 main-jets and it was still a bit too lean...throttle hanging before dropping to idle...made sure the cables had just a bit of slack....not too much...mid to top end was lagging at speed, plug's were bone white! I then changed the main-jets to the supplied 117.5 jet's in the kit, and what an amazing difference! The engine is snappy thru all ranges and run's like a completely different bike! You might also check for air-leak's by spraying WD-40 around carb intakes while engine is running to check for leak's...engine will rev slightly if air-leak's are present....hope this help's!