Shimmed needles, now have idle/RPM issues.

ramykandil · June 15th, 2013, 10:54 PM

Hello, I recently shimmed my needles after reading how people felt like they had a "new bike" after shimming. My bike ran perfectly fine (2009) before shim - never needed choke for a start either.

I shimmed 2 washers and removed snorkel. Used the SAE #4 washers.
My issue is that I have a lower idle than I usually did. If I raise the idle with the knob and get it to 1.3-1.5, when my RPMs are supposed to fall, they hang for a bit then fall very slowly and sometimes sit higher than what the idle was before I took off from my last position. If I leave the idle at 1k, the rpms fall normally when I'm in neutral, but it feels like the bike will die with it idling lower than normal

After shimming I have a harder time starting the bike, choke is necessary, RPMS/idle aren't functioning as they should. I also smell much more gas from my exhaust than I usually do. Doesn't this mean I'm running rich? And if I'm running rich why do I need choke now when I didn't before... doesn't choke enrich the system? I also feel more power from past 6.5-7k rpms, almost like VTEC kicking in.

Help

JELY1990 · June 15th, 2013, 11:38 PM

If your bike was running fine before then put the snorkel back and take the washers off. Your bike is running too rich now.

DaBlue1 · June 16th, 2013, 04:44 AM

Remove the snorkel if you have not already and adjust your idle speed after the bike is fully warmed. Use of the choke is normal when the bike is cold. Since your bike is a 2009 you may also want to replace your air filter. Kawasaki recommends replacement @ 2 years.

ninja250r81 · June 16th, 2013, 05:21 AM

Quote:

Originally Posted by JELY1990

If your bike was running fine before then put the snorkel back and take the washers off. Your bike is running too rich now.

before you do anything,

"I will get flamed" - remove the air filter, then ride it around the block or a few streets and see how the bike responds.

then take off the snorkel, then ride it around the block or a few streets and see how the bike responds.

still crap take it to a proper motorcycle tuner, not mechanic.

why did you mod the tune of the bike to start with????

choneofakind · June 16th, 2013, 06:32 AM

Woah people. Looks like we have a novice carb tuner. Before we all make suggestions on what else to modify/putting back to normal let's get some background info on the carbs and make sure the easy stuff is covered. The idea here is not to confuse the heck out of our new posters with too much info or bad info (why suggest going back to stock???).

okay.

Adjusting the fueling in a carb is not as simple as 'it's rich' or 'it's lean'. There are 3 main parts to tuning a carb; the main jets, the needle height/thickness, and the idle mixture. You can be lean in one of those areas and balls rich in another (like the stock setup) and not perform well because of it. The stock main jets are too rich. Snorkel removal is meant to lean that top end just a bit so that it pulls harder. However this leans the fuel mixture all over the rpm/throttle range. Since the stock needle height is a touch low to start with (a little lean in the midrange) that means that the mid-range is a little bit more lean after snorkel removal. That's where shimming comes in. Raising the needle height just a bit enriches that mixture in the mid-throttle openings.

Seeing a trend? Adjust air, adjust fuel to compensate.

The trick is to separate your diagnosing into specific tests that allow you to test only one part of the carburetor at a time. This is very important, or else you'll get confused and mind-blown, which I can see is already happening. From my experience, removing the air filter and/or covering part of the intake is the 'rough and dirty' way of checking mixture. There are many better ways of doing it that don't require worrying about unfiltered air getting sucked into your engine.

here's a way of tuning the carbs and tests for how to determine the mixture from each part of the carburetor:
http://www.factorypro.com/tech_tunin...m_engines.html

also, here's info on how CV carburetors work:
http://faq.ninja250.org/wiki/How_a_c...arbs_explained

When adjusting fueling, remember the order:
1) Main jets
2) needle height
3) mix screws (float height here as well, but you're fine. We won't get into that)

Remember that needing or not needing choke is not a measure of health of the engine. All engines need more fuel when cold in order to warm up. Period. If you're not using choke when starting for the first time of the day, you should be. It will make your starts easier and your warm-up period (while riding easy) much smoother/quicker. Using choke also allows you to raise your idle when the engine is cold.

Also remember that idle should not be set until the engine is 100% up to temp. Don't mess with the idle speed knob until the engine is hot. Additionally, smelling some unburnt gasoline is normal with motorcycles that have had the fuel adjusted. Don't worry about that unless the bike bogs and dies or if it's REALLY smelly and blowing smoke. A little morning breath isn't an issue, it's just a part of motorcycling and carburetors.

For now, check to make sure that all your connections are still the way they were before you started. Make sure you put everything together properly. Make sure you didn't tear a diaphragm. Do the easy stuff first. After that, if that doesn't work, I'll have you do some testing to make sure that the needle height is correct. Then we'll adjust the idle mix (if needed)

Did that help a bit?

ramykandil · June 16th, 2013, 07:10 AM

Yes, thank you for your input and suggestions.

I do have a question I would love answered though- why do my RPMS "float" and fall down very slowly? Someone has to know the cause behind this!

DaBlue1 · June 16th, 2013, 07:28 AM

Quote:

Originally Posted by ramykandil

..... why do my RPMS "float" and fall down very slowly?

Vacuum. As long as there is enough vacuum on the carbs the diaphragms continue to stay open (or in the up position.) Open diaphragms allow more air and fuel into combustion.

Here is some good detailed info.

How Constant Velocity Carburetors Work
http://www.motorcycleproject.com/mot...bs_work_v3.swf

Motorcycle Carburetor Theory 101
http://www.motorcyclecarbs.com/carbs101.pdf

Carburetor Jet Tech
http://www.motorcycleproject.com/mot...et_tech_v3.swf

choneofakind · June 16th, 2013, 07:34 AM

^^^ This also brings us to a test we can do to check the idle mix. The idea is to blip it at idle and see how it responds and comes back to idle. If it hangs high, then drops slowly, the idle mix is a bit lean. If it drops rapidly, sinks below the desired idle, and then comes back up again, then idle mix is a bit rich.

Don't worry about that for now. Read through the Factory Pro tuning guide I linked and test the needle height (in this case, the height is controlled by washers instead of clip positions) by following their directions. This will make sure the needle height is correct, then we can talk you through testing the pilot jets.

Basically, to test the needle height, do a bunch of gradual roll-ons and roll-offs from about 1/4 throttle to about 3/4 throttle. Do this all over the RPM range. If it's smooth, you're good. If it hesitates or surges on really slow roll-on's you need another washer. If it feels soggy or bogs, you need to take a washer off. I've found that taking a curvy road very smoothly and gradually is a good way to test needle height. I've also found that the tell-tale RPM/throttle opening to judge your needle height is a gradual roll-on at about 9k coming out of a gradual curve.

Another way to test needle height, as described by FP:
putt around in 2nd at 2500-3000 rpm. Then whack the throttle wide open. If the engine is smooth and linear the whole way to 10k, you're good. Surging = one more washer, bogging = one less washer. This is a good test of the needle height on CV carbs because the slides don't open up immediately. They open gradually to keep the Velocity constant (hence, CV, or Constant Velocity) as such, you'll notice if the needle is too high or too low as the slides and needles rise out of the main jet because you'll feel it in how the bike pulls in the mid-range.

Blue's links for reading are good as well, likely better than the ones I posted.

DaBlue1 · June 16th, 2013, 08:07 AM

It is not uncommon for the idle to have to be readjusted for seasonal temp changes. Depending on where in Northern VA you live, you may need to change it (idle speed) up or down according to the weather (Temp changes). Hi 50's -low 60 degree temps in the morning to 80-90 degrees in the evening is a big enough change to affect how a carb'd bike runs at idle. Since carbs can't adjust for temp changes automatically, you need to do it manually.

menikmati · June 16th, 2013, 12:15 PM

Quote:

Originally Posted by choneofakind

Another way to test needle height, as described by FP:
putt around in 2nd at 2500-3000 rpm. Then whack the throttle wide open. If the engine is smooth and linear the whole way to 10k, you're good. Surging = one more washer, bogging = one less washer. This is a good test of the needle height on CV carbs because the slides don't open up immediately. They open gradually to keep the Velocity constant (hence, CV, or Constant Velocity) as such, you'll notice if the needle is too high or too low as the slides and needles rise out of the main jet because you'll feel it in how the bike pulls in the mid-range.

I've always wondered what the difference between surging and bogging is?

choneofakind · June 16th, 2013, 04:41 PM

surging hesitates then lunges repeatedly. Bogging just kinda chuggs and has to fight its way through the extra fuel.

Motofool · July 3rd, 2013, 10:25 AM

Quote:

Originally Posted by DaBlue1

............
Carburetor Jet Tech
~~http://www.motorcycleproject.com/mot...et_tech_v3.swf~~

Just fixed non-working link

http://www.motorcycleproject.com/mot...et_tech_v3.swf

Lots of great info in this thread !!!

June 15th, 2013, 10:54 PM	#1
ramykandil ninjette.org member Name: ramy Location: nova Join Date: Jun 2013 Motorcycle(s): 09 250 Posts: 18	Shimmed needles, now have idle/RPM issues. Hello, I recently shimmed my needles after reading how people felt like they had a "new bike" after shimming. My bike ran perfectly fine (2009) before shim - never needed choke for a start either. I shimmed 2 washers and removed snorkel. Used the SAE #4 washers. My issue is that I have a lower idle than I usually did. If I raise the idle with the knob and get it to 1.3-1.5, when my RPMs are supposed to fall, they hang for a bit then fall very slowly and sometimes sit higher than what the idle was before I took off from my last position. If I leave the idle at 1k, the rpms fall normally when I'm in neutral, but it feels like the bike will die with it idling lower than normal After shimming I have a harder time starting the bike, choke is necessary, RPMS/idle aren't functioning as they should. I also smell much more gas from my exhaust than I usually do. Doesn't this mean I'm running rich? And if I'm running rich why do I need choke now when I didn't before... doesn't choke enrich the system? I also feel more power from past 6.5-7k rpms, almost like VTEC kicking in. Help

June 16th, 2013, 06:32 AM	#5
choneofakind ninjette.org certified postwhore Name: . Location: . Join Date: Feb 2011 Motorcycle(s): . Posts: Too much. MOTM - Feb '13, Feb '14	Woah people. Looks like we have a novice carb tuner. Before we all make suggestions on what else to modify/putting back to normal let's get some background info on the carbs and make sure the easy stuff is covered. The idea here is not to confuse the heck out of our new posters with too much info or bad info (why suggest going back to stock???). okay. Adjusting the fueling in a carb is not as simple as 'it's rich' or 'it's lean'. There are 3 main parts to tuning a carb; the main jets, the needle height/thickness, and the idle mixture. You can be lean in one of those areas and balls rich in another (like the stock setup) and not perform well because of it. The stock main jets are too rich. Snorkel removal is meant to lean that top end just a bit so that it pulls harder. However this leans the fuel mixture all over the rpm/throttle range. Since the stock needle height is a touch low to start with (a little lean in the midrange) that means that the mid-range is a little bit more lean after snorkel removal. That's where shimming comes in. Raising the needle height just a bit enriches that mixture in the mid-throttle openings. Seeing a trend? Adjust air, adjust fuel to compensate. The trick is to separate your diagnosing into specific tests that allow you to test only one part of the carburetor at a time. This is very important, or else you'll get confused and mind-blown, which I can see is already happening. From my experience, removing the air filter and/or covering part of the intake is the 'rough and dirty' way of checking mixture. There are many better ways of doing it that don't require worrying about unfiltered air getting sucked into your engine. here's a way of tuning the carbs and tests for how to determine the mixture from each part of the carburetor: http://www.factorypro.com/tech_tunin...m_engines.html also, here's info on how CV carburetors work: http://faq.ninja250.org/wiki/How_a_c...arbs_explained When adjusting fueling, remember the order: 1) Main jets 2) needle height 3) mix screws (float height here as well, but you're fine. We won't get into that) Remember that needing or not needing choke is not a measure of health of the engine. All engines need more fuel when cold in order to warm up. Period. If you're not using choke when starting for the first time of the day, you should be. It will make your starts easier and your warm-up period (while riding easy) much smoother/quicker. Using choke also allows you to raise your idle when the engine is cold. Also remember that idle should not be set until the engine is 100% up to temp. Don't mess with the idle speed knob until the engine is hot. Additionally, smelling some unburnt gasoline is normal with motorcycles that have had the fuel adjusted. Don't worry about that unless the bike bogs and dies or if it's REALLY smelly and blowing smoke. A little morning breath isn't an issue, it's just a part of motorcycling and carburetors. For now, check to make sure that all your connections are still the way they were before you started. Make sure you put everything together properly. Make sure you didn't tear a diaphragm. Do the easy stuff first. After that, if that doesn't work, I'll have you do some testing to make sure that the needle height is correct. Then we'll adjust the idle mix (if needed) Did that help a bit? Last futzed with by choneofakind; June 16th, 2013 at 07:38 AM.
	1 out of 1 members found this post helpful.

June 16th, 2013, 07:34 AM	#8
choneofakind ninjette.org certified postwhore Name: . Location: . Join Date: Feb 2011 Motorcycle(s): . Posts: Too much. MOTM - Feb '13, Feb '14	^^^ This also brings us to a test we can do to check the idle mix. The idea is to blip it at idle and see how it responds and comes back to idle. If it hangs high, then drops slowly, the idle mix is a bit lean. If it drops rapidly, sinks below the desired idle, and then comes back up again, then idle mix is a bit rich. Don't worry about that for now. Read through the Factory Pro tuning guide I linked and test the needle height (in this case, the height is controlled by washers instead of clip positions) by following their directions. This will make sure the needle height is correct, then we can talk you through testing the pilot jets. Basically, to test the needle height, do a bunch of gradual roll-ons and roll-offs from about 1/4 throttle to about 3/4 throttle. Do this all over the RPM range. If it's smooth, you're good. If it hesitates or surges on really slow roll-on's you need another washer. If it feels soggy or bogs, you need to take a washer off. I've found that taking a curvy road very smoothly and gradually is a good way to test needle height. I've also found that the tell-tale RPM/throttle opening to judge your needle height is a gradual roll-on at about 9k coming out of a gradual curve. Another way to test needle height, as described by FP: putt around in 2nd at 2500-3000 rpm. Then whack the throttle wide open. If the engine is smooth and linear the whole way to 10k, you're good. Surging = one more washer, bogging = one less washer. This is a good test of the needle height on CV carbs because the slides don't open up immediately. They open gradually to keep the Velocity constant (hence, CV, or Constant Velocity) as such, you'll notice if the needle is too high or too low as the slides and needles rise out of the main jet because you'll feel it in how the bike pulls in the mid-range. Blue's links for reading are good as well, likely better than the ones I posted.
	1 out of 1 members found this post helpful.

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June 15th, 2013, 11:38 PM	#2
JELY1990 Boring is my middle name. Name: Jason Location: Bay Area, CA Join Date: Aug 2011 Motorcycle(s): '09 Ninja 250r Posts: 258	If your bike was running fine before then put the snorkel back and take the washers off. Your bike is running too rich now.

June 16th, 2013, 04:44 AM	#3
DaBlue1 Long Time Rider Name: Blue Location: Charlotte, NC Join Date: Sep 2010 Motorcycle(s): 2009 Kawasaki Ninja 250R Posts: A lot.	Remove the snorkel if you have not already and adjust your idle speed after the bike is fully warmed. Use of the choke is normal when the bike is cold. Since your bike is a 2009 you may also want to replace your air filter. Kawasaki recommends replacement @ 2 years.

June 16th, 2013, 07:10 AM	#6
ramykandil ninjette.org member Name: ramy Location: nova Join Date: Jun 2013 Motorcycle(s): 09 250 Posts: 18	Yes, thank you for your input and suggestions. I do have a question I would love answered though- why do my RPMS "float" and fall down very slowly? Someone has to know the cause behind this!

June 16th, 2013, 08:07 AM	#9
DaBlue1 Long Time Rider Name: Blue Location: Charlotte, NC Join Date: Sep 2010 Motorcycle(s): 2009 Kawasaki Ninja 250R Posts: A lot.	It is not uncommon for the idle to have to be readjusted for seasonal temp changes. Depending on where in Northern VA you live, you may need to change it (idle speed) up or down according to the weather (Temp changes). Hi 50's -low 60 degree temps in the morning to 80-90 degrees in the evening is a big enough change to affect how a carb'd bike runs at idle. Since carbs can't adjust for temp changes automatically, you need to do it manually.

June 16th, 2013, 04:41 PM	#11
choneofakind ninjette.org certified postwhore Name: . Location: . Join Date: Feb 2011 Motorcycle(s): . Posts: Too much. MOTM - Feb '13, Feb '14	surging hesitates then lunges repeatedly. Bogging just kinda chuggs and has to fight its way through the extra fuel.