Rich vs. Lean question

gamma500 · October 17th, 2009, 12:47 PM

Wonder if I could get some feedback on the following. My 08 Ninja seemed less "cold blooded" from the factory. Put 1 washer in and desnorkled to richen things up in the intermediate-high range and she ran fine. Replaced the stock exhaust with Matt's VR6 and she ran fine..a bit "finer" at top end with more "pull". Plug color was light brown on electrode, a bit pale on insulator. Put the snorkel back in to "richen" things up and she wouldn't pull past 8K rpms...just crackled and fell flat in all gears. Removed snorkel and life was good again.

Any thoughts on what went on there ?

kkim · October 17th, 2009, 12:52 PM

sounds like your mixture went too rich when you restricted the air intake with the snorkel.

Step 1: Find the proper main jet.
Note that you will have to buy 2 jets of each size, one per carburetor. Start from the stock jet and needle height, and increase the main jet size by ONE SIZE at a time, until you feel the upper too rich. Then back up to the previous size. Please note that the amount of gas passed by the main jet increases exponentially with main jet size, as the circumference of a circle increases exponentially with diameter! What that means is that the difference between jet sizes is not equal.

Example:

~Start from stock.

~#105=Way too lean. Bike won't rev past 6K RPMs.

~#108=Bike revs to redline, but sputters at high RPMs.

~#110=Bike pulls hard to redline.

~#114=Bike bogs at high RPMs.

~Go back one size to #110s.

Symptoms:

LEAN = Stuttering. Runs better when bike is hot. White plugs.

RICH = Bogging. Runs better when bike is cold. Black plugs.

[edit]Step 2: Find the proper needle height.
Start from the tuned jet that you decided on in step 1. Use the stock needle height, and keep raising the needles by adding washers. If it runs better with more washers, then, when you get to about 4, go up a size on the main jets and start with the stock needle height again.

Even after you get the main jet correct, you will often end up with a midrange stumble at 5k-6k rpm. This has little to do with main jet size. You can take care of it by adjusting the needle height. Lower the needle until you get a mid-range stumble, then raise it by 1 washer at a time until you get rid of the stumble.

Symptoms:

LEAN = Stuttering. Runs better when bike is hot. White plugs.

RICH = Bogging. Runs better when bike is cold. Black plugs.

gamma500 · October 17th, 2009, 01:44 PM

Thanks for your time...I guess I am confused by how to tell the difference between my making the bike richer(resnorkling) and not being able to rev past 8K...it just "bogged" here and the "too lean, won't rev past X rpms". How would you describe the feel of a "bog" versus a "stutter" ?

kkim · October 17th, 2009, 03:23 PM

Quote:

Originally Posted by gamma500

How would you describe the feel of a "bog" versus a "stutter" ?

To me, a bog is like the bike goes into a black hole and the power goes flat. A stutter is like the power goes in and out at a rapid rate.

Try holding the rpms at a certain rpm and it will be more evident than trying to accelerate through that particular rpm.

g21-30 · October 17th, 2009, 04:53 PM

Check the second paragraph in this article:

http://www.thecarburetorshop.com/Troubleshooting.htm

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October 17th, 2009, 12:47 PM	#1
gamma500 ninjette.org member Name: Craig Location: Asheville, NC Join Date: Aug 2009 Motorcycle(s): 2008 Ninja 250R Posts: 98	Rich vs. Lean question Wonder if I could get some feedback on the following. My 08 Ninja seemed less "cold blooded" from the factory. Put 1 washer in and desnorkled to richen things up in the intermediate-high range and she ran fine. Replaced the stock exhaust with Matt's VR6 and she ran fine..a bit "finer" at top end with more "pull". Plug color was light brown on electrode, a bit pale on insulator. Put the snorkel back in to "richen" things up and she wouldn't pull past 8K rpms...just crackled and fell flat in all gears. Removed snorkel and life was good again. Any thoughts on what went on there ?

October 17th, 2009, 12:52 PM	#2
kkim Join Date: Nov 2008 Posts: Too much.	sounds like your mixture went too rich when you restricted the air intake with the snorkel. Step 1: Find the proper main jet. Note that you will have to buy 2 jets of each size, one per carburetor. Start from the stock jet and needle height, and increase the main jet size by ONE SIZE at a time, until you feel the upper too rich. Then back up to the previous size. Please note that the amount of gas passed by the main jet increases exponentially with main jet size, as the circumference of a circle increases exponentially with diameter! What that means is that the difference between jet sizes is not equal. Example: ~Start from stock. ~#105=Way too lean. Bike won't rev past 6K RPMs. ~#108=Bike revs to redline, but sputters at high RPMs. ~#110=Bike pulls hard to redline. ~#114=Bike bogs at high RPMs. ~Go back one size to #110s. Symptoms: LEAN = Stuttering. Runs better when bike is hot. White plugs. RICH = Bogging. Runs better when bike is cold. Black plugs. [edit]Step 2: Find the proper needle height. Start from the tuned jet that you decided on in step 1. Use the stock needle height, and keep raising the needles by adding washers. If it runs better with more washers, then, when you get to about 4, go up a size on the main jets and start with the stock needle height again. Even after you get the main jet correct, you will often end up with a midrange stumble at 5k-6k rpm. This has little to do with main jet size. You can take care of it by adjusting the needle height. Lower the needle until you get a mid-range stumble, then raise it by 1 washer at a time until you get rid of the stumble. Symptoms: LEAN = Stuttering. Runs better when bike is hot. White plugs. RICH = Bogging. Runs better when bike is cold. Black plugs.

October 17th, 2009, 01:44 PM	#3
gamma500 ninjette.org member Name: Craig Location: Asheville, NC Join Date: Aug 2009 Motorcycle(s): 2008 Ninja 250R Posts: 98	Thanks for your time...I guess I am confused by how to tell the difference between my making the bike richer(resnorkling) and not being able to rev past 8K...it just "bogged" here and the "too lean, won't rev past X rpms". How would you describe the feel of a "bog" versus a "stutter" ?

October 17th, 2009, 04:53 PM	#5
g21-30 ninjette.org certified postwhore Name: Sam Location: Northern Virginia Join Date: Nov 2008 Motorcycle(s): Ninja 250R 2009 Posts: A lot.	Check the second paragraph in this article: http://www.thecarburetorshop.com/Troubleshooting.htm