Question about jetting/altitude

MauR · July 29th, 2016, 05:53 PM

Hello everyone!!

I have a 2009 250R with a DanMoto Carbon Slip-on.

In the carbs the only modification is 2 shims on each needle and after using the oem exhaust for a few days I noticed that in the low end there is a small loss of power which I asume will be fixed opening the idle screws.

Is this correct??? or should I think on jetting even if there is in no other mod.

It is important to mention that I have checked the jetting database but I ride at 7200ft (2200 meters) and I have not found anything on how altitude would affect the carbs.

Any suggestion will be appreciated. TIA

Lazarus · July 30th, 2016, 03:35 AM

Quote:

Originally Posted by MauR

In the carbs the only modification is 2 shims on each needle and after using the oem exhaust for a few days I noticed that in the low end there is a small loss of power

So you used the OEM exhaust then switched to the Dan moto slip on and noticed the loss of power? Am I interpreting that correctly? If so are your idle mixture screw's out 2.5 turns? You can adjust them out by 1/8-1/4 turn but I wouldn't go any farther than 3 or 3 1/4.

Also, the ninja 250's dont have much low end to begin with and once you put a slip on to free up the top end the low end suffers a little (like robbing peter to pay paul)

Someone may correct me if I'm wrong here but higher elevation means the air is less dense, which requires more fuel. You may want to consider a new main and pilot jet in addition to the shims you have on the needles.

Hope this helps!

Motofool · July 30th, 2016, 04:43 AM

This may help:
http://faq.ninja250.org/wiki/Jetting...26_temperature

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

The color of your sprk plugs can tell you how off your mix is for your specific conditions of altitude and temperature.

NinJim · July 30th, 2016, 07:04 AM

First, fuel flow decreases with altitude. The fuel/air ratio must remain the same for the engine to work at all. So, the higher the elevation = the less air, and less fuel. This is called Density altitude and is made up of air pressure (elevation), temperature, and humidity.

How do you use the bike? Are you mostly less than wide open (WOT)? Or is the bike a track only? This is where you will be WOT most of the time. I raced a 125cc GP bike. We had a little digital temp, baro press, and humidity gauge box to help calculate the density altitude. It was common to change the main jet 5 or more times a day.

I ride between 4,000 and 10,000 on a day ride, which is mostly at mid-throttle. If you have your mixture screw set correctly (meaning the correct pilot jet) for Mex City, you should be good to go up or down 3,000 with no problem. I rode a 250cc two stroke for 4 days last week. We were between 5,000 and 10,400, by just adjusting the mix screw. Yes, there isn't much power left above 10.

Concentrate on getting the idle circuit correct; then the rest will flow. Let the Forum members here help. There's a lot of experience here.

MauR · July 30th, 2016, 04:34 PM

Thanks for your answers.

I use the bike for street only (commuting) so thats why I would like to fix the loss of low end power. RPMs are usually between 3000 - 9000.

Danmoto slip-on helps to be heard by cars around.

If I understand this could be fixed with the idle screw?? Are the pilot jets needed??

At this altitude I could actually reduce the jets, is this right??

Thanks again!!

NinJim · July 31st, 2016, 10:51 AM

Do you have a shop with a Dyno and air/fuel analyzer? This is the best way to determine your lean/rich problem.

When you put your high flow can on the bike, did it come with the two shims for the needle? This will enrich the mid-range, which at sea level is probably needed for the increased air flow through the engine. I'm guessing here, but I think you are too rich.

So, try this... take 1 shim out and ride it, all gears and all throttle settings. Better or worse? If better, take out the second shim and repeat. This should tell you if you are rich or lean.

If this is not effective, then we can get into the idle air screw and pilot jet.
Cheers,

MauR · August 1st, 2016, 02:52 PM

Yesterday I reinstalled the danmoto slip-on. The only thing I changed was the location of the baffle, this time installed in the inlet side (as the exhaust instructions indicates).

This way the power loss is not present. Maybe it is my perception or placing the baffle in the inlet side helps to create some back pressure.

Any way I'll check the spark plugs trying to see if it is running rich due to the two shims or if it is ok.

I Installed the shims after the exhaust and the bike worked better after 7k rpm

July 29th, 2016, 05:53 PM	#1
MauR ninjette.org member Name: Mauricio Location: Mexico City Join Date: Aug 2015 Motorcycle(s): 250R Posts: 86	Question about jetting/altitude Hello everyone!! I have a 2009 250R with a DanMoto Carbon Slip-on. In the carbs the only modification is 2 shims on each needle and after using the oem exhaust for a few days I noticed that in the low end there is a small loss of power which I asume will be fixed opening the idle screws. Is this correct??? or should I think on jetting even if there is in no other mod. It is important to mention that I have checked the jetting database but I ride at 7200ft (2200 meters) and I have not found anything on how altitude would affect the carbs. Any suggestion will be appreciated. TIA

July 30th, 2016, 04:43 AM	#3
Motofool Daily Ninjette rider Name: Hernan Location: Florida Join Date: Mar 2011 Motorcycle(s): 2007 Ninja 250 Posts: A lot. MOTY - 2016, MOTM - Dec '12, Jan '14, Jan '15, May '16	This may help: http://faq.ninja250.org/wiki/Jetting...26_temperature http://faq.ninja250.org/wiki/I_want_...uretor_jetting The color of your sprk plugs can tell you how off your mix is for your specific conditions of altitude and temperature. __________________________________________________ *Motofool* *.................................Never ride faster than your guardian angel can fly* "Mankind is composed of two sorts of men — those who love and create, and those who hate and destroy. Love is the bond between men, the way to teach and the center of the world." - José Martí

July 30th, 2016, 07:04 AM	#4
NinJim ninjette.org member Name: Jim Location: Utah Join Date: Apr 2016 Motorcycle(s): Ninja250-3x; CBR600 & R6 (track bikes); lots of dirt stuff Posts: 25	Riding style first First, fuel flow decreases with altitude. The fuel/air ratio must remain the same for the engine to work at all. So, the higher the elevation = the less air, and less fuel. This is called Density altitude and is made up of air pressure (elevation), temperature, and humidity. How do you use the bike? Are you mostly less than wide open (WOT)? Or is the bike a track only? This is where you will be WOT most of the time. I raced a 125cc GP bike. We had a little digital temp, baro press, and humidity gauge box to help calculate the density altitude. It was common to change the main jet 5 or more times a day. I ride between 4,000 and 10,000 on a day ride, which is mostly at mid-throttle. If you have your mixture screw set correctly (meaning the correct pilot jet) for Mex City, you should be good to go up or down 3,000 with no problem. I rode a 250cc two stroke for 4 days last week. We were between 5,000 and 10,400, by just adjusting the mix screw. Yes, there isn't much power left above 10. Concentrate on getting the idle circuit correct; then the rest will flow. Let the Forum members here help. There's a lot of experience here.

July 31st, 2016, 10:51 AM	#6
NinJim ninjette.org member Name: Jim Location: Utah Join Date: Apr 2016 Motorcycle(s): Ninja250-3x; CBR600 & R6 (track bikes); lots of dirt stuff Posts: 25	How to analyze the problem Do you have a shop with a Dyno and air/fuel analyzer? This is the best way to determine your lean/rich problem. When you put your high flow can on the bike, did it come with the two shims for the needle? This will enrich the mid-range, which at sea level is probably needed for the increased air flow through the engine. I'm guessing here, but I think you are too rich. So, try this... take 1 shim out and ride it, all gears and all throttle settings. Better or worse? If better, take out the second shim and repeat. This should tell you if you are rich or lean. If this is not effective, then we can get into the idle air screw and pilot jet. Cheers,

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July 30th, 2016, 04:34 PM	#5
MauR ninjette.org member Name: Mauricio Location: Mexico City Join Date: Aug 2015 Motorcycle(s): 250R Posts: 86	Thanks for your answers. I use the bike for street only (commuting) so thats why I would like to fix the loss of low end power. RPMs are usually between 3000 - 9000. Danmoto slip-on helps to be heard by cars around. If I understand this could be fixed with the idle screw?? Are the pilot jets needed?? At this altitude I could actually reduce the jets, is this right?? Thanks again!!

August 1st, 2016, 02:52 PM	#7
MauR ninjette.org member Name: Mauricio Location: Mexico City Join Date: Aug 2015 Motorcycle(s): 250R Posts: 86	Yesterday I reinstalled the danmoto slip-on. The only thing I changed was the location of the baffle, this time installed in the inlet side (as the exhaust instructions indicates). This way the power loss is not present. Maybe it is my perception or placing the baffle in the inlet side helps to create some back pressure. Any way I'll check the spark plugs trying to see if it is running rich due to the two shims or if it is ok. I Installed the shims after the exhaust and the bike worked better after 7k rpm