jetting a modded engine

poormanq45 · June 25th, 2012, 06:16 AM

I have a 2006 Ninja 250.

I need help with a few things.

The engine has been bored +2mm and has 12.5:1 pistons in it.

The head has been ported and polished.

3 angle valve job.

Airbox removed(should I go with 4" Pods or the dual inlet KN?)

The main question is where should I start with the jetting? I've read that even with just removing the airbox you could end up using a 112 main. I'm guessing that I should start somewhere around 116? Higher?

Any input is greatly appreciated.

Racer x · June 25th, 2012, 10:58 AM

Start with 117 and you will possibly go as high as 122. I am assuming stock carbs. What pistons do you have?

I like the K&N 0990 filter. But the dual pods are good also. I run stacks with no air filter on the track.

poormanq45 · June 25th, 2012, 01:16 PM

Quote:

Originally Posted by Racer x

Start with 117 and you will possibly go as high as 122. I am assuming stock carbs. What pistons do you have?

I like the K&N 0990 filter. But the dual pods are good also. I run stacks with no air filter on the track.

I ordered the 0990. As this will be used on the street, I need to find an outerwear for it just incase I get caught in the rain.

I installed this JE kit:
http://www.jepistons.com/Products/292754.aspx

Yes, the carbs are stock. I had three shims under the needles. I'll remove those when I change the jets initially.

Racer x · June 25th, 2012, 01:45 PM

OK that is the 265cc kit. That is what I am running. Do a compression test. I have about 180 to 190psi and ran 128 jets in my CR carbs. Plugs are white so I went to 130 jets. Plus I have a Brt ignition. But you have a first gen ignition so we are both running about the same timing. I would love to see what you dyno.

poormanq45 · June 25th, 2012, 03:44 PM

Quote:

Originally Posted by Racer x

OK that is the 265cc kit. That is what I am running. Do a compression test. I have about 180 to 190psi and ran 128 jets in my CR carbs. Plugs are white so I went to 130 jets. Plus I have a Brt ignition. But you have a first gen ignition so we are both running about the same timing. I would love to see what you dyno.

I'll report back with the compression.

I haven't mounted the engine on the frame yet. I'm getting together a few miscellaneous parts.

What would you suggest for the exhaust? I'm annoyed that the systems for this bike are relatively expensive. I was thinking about hollowing out the cans and putting in a perforated core with muffler packing in them. Just like a dirt bike.

Racer x · June 25th, 2012, 06:34 PM

I don't know. I am lost on exhaust system I have a two into two with megaphones. I had to baffle it up because of the noise. Now I need to go on the dyno to test how much baffle to remove,

Two things I will say.
One The 250 ninja engine is loud . I don't know why but if you take off the muffler on these engines the volume is shocking.
The other thing I found from dyno testing is the back pressure is important to the power. taking of the can and running open pipes under the engine, lost two or three hp. Not because it was lean, I re jetted and the AF was good . Power was down. Same with a two into one with a little L pipe under the engine it Lost power.

The fastest 2008 ninja 250 went 117 mph and had a Nojime Street muffler on it.And was quiet. Little engines are very sensitive to power bands and the exhaust changes that a lot. I just made something that looks kool.

alex.s · June 25th, 2012, 07:09 PM

eric, the past few months i've been trying to find information about 4 strokes and back pressure and their relationship... but been failing on finding any decent information. can you recommend any good books or online resources on the fluid dynamics related to exhaust gas?

Racer x · June 25th, 2012, 07:34 PM

Nope, I wish I could. I am going from what Honda and MV Agusta did during the sixties and sevenths. Before the two stroke and as they competed with the two strokes . A ton of resurch was done. The exhaust on my bike is a 1957 MV Agusta 500cc four with the same bore and stroke as our ninja. I coppiex the exhaust length and guesed the distance from carb inlet to valve

Somchai · June 25th, 2012, 08:06 PM

Don't forget about the resonance or the pulsation because this is also very important for a good exhaust-system.

Racer x · June 26th, 2012, 02:23 AM

The resonance is key . The length of the exhaust pipe is critical to proper scavaging. Scaviging is when ,like a syphon the exhaust pulse is traveling down the pipe then the next exhaust pulse comes and gets pulled along. Getting the exhaust valve open at the right time the length of the pipes all of this will contribute to determine the Power band.

I would like to spend a month playing on a dyno changing exhaust shape and cam timing.

poormanq45 · June 26th, 2012, 08:28 AM

Alright, I'm looking at jets on this page right now:
http://www.jetsrus.com/a_jet_kit_str...X250_Ninja.htm

I've worked on carbs in terms of tearing them apart for cleaning, but never much in the way of what we're dealing with here.

Pretty much if you tell me what ones to order, I'll order them.

It seems I'm looking at:
118
120
122
more?

What about the pilot jets?

Racer x · June 26th, 2012, 10:28 AM

I run a 48 pilot on the stock carbs but that was a 249 cc engine with 12.5 to 1 since you have 265cc you might want to go richer in the midrange. I don't have that much experience tuning the first gen engine.

If you have jetting up to 116 then get the rest up to 122. What plugs are you going with. I run cr9 e

poormanq45 · June 26th, 2012, 11:00 AM

Quote:

Originally Posted by Racer x

I run a 48 pilot on the stock carbs but that was a 249 cc engine with 12.5 to 1 since you have 265cc you might want to go richer in the midrange. I don't have that much experience tuning the first gen engine.

If you have jetting up to 116 then get the rest up to 122. What plugs are you going with. I run cr9 e

I didn't even think about changing to a different plug.

Details on that?

I was probably going to just run the stock ones, but in NGK Iridium variant.

*edit* Just to make sure I understand you, You're saying get all Main jets from 118 to 122? And then the pilot 50, 52 and maybe even 55?

*edit 2* Before this rebuild, I was in completely stock form with just 3 washers under the needles. So I don't have any jets or anything on hand.

poormanq45 · June 26th, 2012, 11:37 AM

Ok, after reading up on the different jets some more I've come to this idea:

With the pilot jet I just need something that flows more than enough. We could use the mixture screw to adjust it down. I just have to make sure that at 100% flow, screw all the way out, we have more fuel being dumped than needed. We just adjust down from there.

With that said, I'm thinking of just ordering a single pair of pilot jets.

Thoughts on 50?

Thoughts on my thinking?

Racer x · June 26th, 2012, 11:55 AM

That all sounds good 50 pilot and Maybe 122 for the mains. I bet the 118 will be good but jets are cheaper than shipping. As for plugs I want a colder plug. Iridium is ok but hard to read.

poormanq45 · June 26th, 2012, 06:38 PM

Someone on another forum finally responded to my thread. He's suggesting that the pilot jet should be much smaller.

Any info on this? Is it possible that your numbers and his are so different because you're on a newer generation bike?

http://forums.ninja250.org/viewtopic.php?t=87614

Racer x · June 26th, 2012, 08:10 PM

I can't recall is the stock pilot jet 38 or 48? I would only go up one jet size. But I think it is a bigger number for a larger volume. Ask jets are us they are great. I also use the carb warehouse.

poormanq45 · June 26th, 2012, 08:24 PM

I believe it is 38.

I'll email them and see.

JE is pretty useless. I messaged them asking about octane for the 13.5:1 kit and they claimed I'd have to run over 100 octane and that even for the 12.5:1 kit I should be at ~97 octane.

Ugh, the stock bike is 12.4:1 and uses 87!

June 25th, 2012, 06:16 AM	#1
poormanq45 ninjette.org newbie Name: Brien Location: Florida Join Date: Jun 2012 Motorcycle(s): 2006 Ninja 250 Posts: 8	jetting a modded engine I have a 2006 Ninja 250. I need help with a few things. The engine has been bored +2mm and has 12.5:1 pistons in it. The head has been ported and polished. 3 angle valve job. Airbox removed(should I go with 4" Pods or the dual inlet KN?) The main question is where should I start with the jetting? I've read that even with just removing the airbox you could end up using a 112 main. I'm guessing that I should start somewhere around 116? Higher? Any input is greatly appreciated.

June 25th, 2012, 07:09 PM	#7
alex.s wat Name: wat Location: tustin/long beach Join Date: Sep 2009 Motorcycle(s): wat Posts: Too much. Blog Entries: 5 MOTM - Oct '12, Feb '14	eric, the past few months i've been trying to find information about 4 strokes and back pressure and their relationship... but been failing on finding any decent information. can you recommend any good books or online resources on the fluid dynamics related to exhaust gas? __________________________________________________

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June 25th, 2012, 10:58 AM	#2
Racer x ninjette.org certified postwhore Name: Eric Location: Iowa City Join Date: May 2009 Motorcycle(s): 2008 Kawmeracchi 350 2010 Project X Posts: A lot. Blog Entries: 54 MOTM - Sep '18, Feb '16	Start with 117 and you will possibly go as high as 122. I am assuming stock carbs. What pistons do you have? I like the K&N 0990 filter. But the dual pods are good also. I run stacks with no air filter on the track.

June 25th, 2012, 01:45 PM	#4
Racer x ninjette.org certified postwhore Name: Eric Location: Iowa City Join Date: May 2009 Motorcycle(s): 2008 Kawmeracchi 350 2010 Project X Posts: A lot. Blog Entries: 54 MOTM - Sep '18, Feb '16	OK that is the 265cc kit. That is what I am running. Do a compression test. I have about 180 to 190psi and ran 128 jets in my CR carbs. Plugs are white so I went to 130 jets. Plus I have a Brt ignition. But you have a first gen ignition so we are both running about the same timing. I would love to see what you dyno.

June 25th, 2012, 06:34 PM	#6
Racer x ninjette.org certified postwhore Name: Eric Location: Iowa City Join Date: May 2009 Motorcycle(s): 2008 Kawmeracchi 350 2010 Project X Posts: A lot. Blog Entries: 54 MOTM - Sep '18, Feb '16	I don't know. I am lost on exhaust system I have a two into two with megaphones. I had to baffle it up because of the noise. Now I need to go on the dyno to test how much baffle to remove, Two things I will say. One The 250 ninja engine is loud . I don't know why but if you take off the muffler on these engines the volume is shocking. The other thing I found from dyno testing is the back pressure is important to the power. taking of the can and running open pipes under the engine, lost two or three hp. Not because it was lean, I re jetted and the AF was good . Power was down. Same with a two into one with a little L pipe under the engine it Lost power. The fastest 2008 ninja 250 went 117 mph and had a Nojime Street muffler on it.And was quiet. Little engines are very sensitive to power bands and the exhaust changes that a lot. I just made something that looks kool.

June 25th, 2012, 07:34 PM	#8
Racer x ninjette.org certified postwhore Name: Eric Location: Iowa City Join Date: May 2009 Motorcycle(s): 2008 Kawmeracchi 350 2010 Project X Posts: A lot. Blog Entries: 54 MOTM - Sep '18, Feb '16	Nope, I wish I could. I am going from what Honda and MV Agusta did during the sixties and sevenths. Before the two stroke and as they competed with the two strokes . A ton of resurch was done. The exhaust on my bike is a 1957 MV Agusta 500cc four with the same bore and stroke as our ninja. I coppiex the exhaust length and guesed the distance from carb inlet to valve

June 25th, 2012, 08:06 PM	#9
Somchai Freedom for Germany Location: This World Join Date: May 2011 Motorcycle(s): Ninja 250R-FI Posts: A lot.	Don't forget about the resonance or the pulsation because this is also very important for a good exhaust-system.

June 26th, 2012, 02:23 AM	#10
Racer x ninjette.org certified postwhore Name: Eric Location: Iowa City Join Date: May 2009 Motorcycle(s): 2008 Kawmeracchi 350 2010 Project X Posts: A lot. Blog Entries: 54 MOTM - Sep '18, Feb '16	The resonance is key . The length of the exhaust pipe is critical to proper scavaging. Scaviging is when ,like a syphon the exhaust pulse is traveling down the pipe then the next exhaust pulse comes and gets pulled along. Getting the exhaust valve open at the right time the length of the pipes all of this will contribute to determine the Power band. I would like to spend a month playing on a dyno changing exhaust shape and cam timing.

June 26th, 2012, 08:28 AM	#11
poormanq45 ninjette.org newbie Name: Brien Location: Florida Join Date: Jun 2012 Motorcycle(s): 2006 Ninja 250 Posts: 8	Alright, I'm looking at jets on this page right now: http://www.jetsrus.com/a_jet_kit_str...X250_Ninja.htm I've worked on carbs in terms of tearing them apart for cleaning, but never much in the way of what we're dealing with here. Pretty much if you tell me what ones to order, I'll order them. It seems I'm looking at: 118 120 122 more? What about the pilot jets?

June 26th, 2012, 10:28 AM	#12
Racer x ninjette.org certified postwhore Name: Eric Location: Iowa City Join Date: May 2009 Motorcycle(s): 2008 Kawmeracchi 350 2010 Project X Posts: A lot. Blog Entries: 54 MOTM - Sep '18, Feb '16	I run a 48 pilot on the stock carbs but that was a 249 cc engine with 12.5 to 1 since you have 265cc you might want to go richer in the midrange. I don't have that much experience tuning the first gen engine. If you have jetting up to 116 then get the rest up to 122. What plugs are you going with. I run cr9 e

June 26th, 2012, 11:37 AM	#14
poormanq45 ninjette.org newbie Name: Brien Location: Florida Join Date: Jun 2012 Motorcycle(s): 2006 Ninja 250 Posts: 8	Ok, after reading up on the different jets some more I've come to this idea: With the pilot jet I just need something that flows more than enough. We could use the mixture screw to adjust it down. I just have to make sure that at 100% flow, screw all the way out, we have more fuel being dumped than needed. We just adjust down from there. With that said, I'm thinking of just ordering a single pair of pilot jets. Thoughts on 50? Thoughts on my thinking?

June 26th, 2012, 11:55 AM	#15
Racer x ninjette.org certified postwhore Name: Eric Location: Iowa City Join Date: May 2009 Motorcycle(s): 2008 Kawmeracchi 350 2010 Project X Posts: A lot. Blog Entries: 54 MOTM - Sep '18, Feb '16	That all sounds good 50 pilot and Maybe 122 for the mains. I bet the 118 will be good but jets are cheaper than shipping. As for plugs I want a colder plug. Iridium is ok but hard to read.

June 26th, 2012, 06:38 PM	#16
poormanq45 ninjette.org newbie Name: Brien Location: Florida Join Date: Jun 2012 Motorcycle(s): 2006 Ninja 250 Posts: 8	Someone on another forum finally responded to my thread. He's suggesting that the pilot jet should be much smaller. Any info on this? Is it possible that your numbers and his are so different because you're on a newer generation bike? http://forums.ninja250.org/viewtopic.php?t=87614

June 26th, 2012, 08:10 PM	#17
Racer x ninjette.org certified postwhore Name: Eric Location: Iowa City Join Date: May 2009 Motorcycle(s): 2008 Kawmeracchi 350 2010 Project X Posts: A lot. Blog Entries: 54 MOTM - Sep '18, Feb '16	I can't recall is the stock pilot jet 38 or 48? I would only go up one jet size. But I think it is a bigger number for a larger volume. Ask jets are us they are great. I also use the carb warehouse.

June 26th, 2012, 08:24 PM	#18
poormanq45 ninjette.org newbie Name: Brien Location: Florida Join Date: Jun 2012 Motorcycle(s): 2006 Ninja 250 Posts: 8	I believe it is 38. I'll email them and see. JE is pretty useless. I messaged them asking about octane for the 13.5:1 kit and they claimed I'd have to run over 100 octane and that even for the 12.5:1 kit I should be at ~97 octane. Ugh, the stock bike is 12.4:1 and uses 87!