2006 needle vs 2005 2004 etc

DandyDan has done a great jetting write-up in the How-to section that you should read. But basically, if your scoot runs better when its cold out, you have a rich mixture. If it runs better when its warmer, its lean.

Also, I've been going up pilot jet sizes, so I know I was on the rich side. My ruk was lagging a bit and I knew it could not be because it was lean.

Don't know about the '06 carb and why the needle is longer. Others have asked too.

Our carb is a CV type carb which means when you twist the throttle you are NOT pulling the needle up and out of the main jet like you used to on older carbs. Instead, the needle pulls up on it's own because when you open the throttle you just open the butterfly valve which lets more air/fuel mix into the engine and does weird things to the air pressure which causes the needle to rise and the perfect speed.

Anyways, my understanding is that the pre-06 needles were a little to short and stubby so the needle would have to rise up less before it was all the way out of the main jet. This gets you to the max gas flow quicker but unfortunately, too quick. The 06 needles are longer and more tapered which means they need to be lifted up futher to get fully out of the main jet and let it flow it's max. The result is that things are a bit smoother because it doesn't overload your carb with gas like the old needle does a bit. So to answer your 2nd question Jasper, the new needles are longer and more gradually tapered so that your gas is increased more gradually so it runs better as you accelerate rather than dumping too much gas in and the pre-06 needle pulls out too fast.

I could be missing something but I don't see how this has anything to do with the new PCV system which is just a ventilation system for your engine to clear the fumes out and prevent oil contamination.

About your first question, how do you know if it's running rich or lean?

Well, as I'm sure you've heard, you can look at the spark plug and black/sooty = rich whereas white = lean but I realize that doesn't really help you in the midrange cuz you can't hold it there long enough to get the plug to change color.

In generally, when your engine is running rich it makes more of a muffled, dull, bogging sound whereas when it's lean it has more of a sharper, popping, harsh exhaust note. However, this is tough to discern even with an aftermarket pipe which is way louder. I forget which pipe you have but if you're using the stock pipe then it would take a really trained ear.

So I haven't really answered you're question yet....I'd say there are two ways to tell which should work for you. The first way is comparing it in cold vs. hot weather. Cold things contract so cold weather = denser air = more oxygen. So if you are normally rich in the midrange, when it's cold out you'll be less rich because of the extra oxygen and it should run better. Conversely, if you are lean, the cold, dense air with extra oxygen will make you even leaner so you'll run worse. Don't try and make any judgements in the first 15min of your riding because you want the engine to be fully warmed up before you judge it. So in summary, when riding in colder than average conditions, if you're rich normally you should run better but if your lean normally, it should run even worse.

Secondly, a perhaps even easier to do is just to change your jetting and see if things get better or worse. For the midrange, I like to play with the slow jets because they are always open so if you go up a size you know for 100% sure that you are getting more gas and thus should be richer. If your Ruckus is running bad in the midrange I'd suggest going up 2 slow jet sizes (ie 35 to 40) so that it's significantly different. You can fine tune later...

Then go for a 15min ride to warm it up and then compare how it runs. If was crappy before you did this and now it's worse, you were rich before whereas if you running crappy before and now it's better, you where lean. Does that make sense?

But with a CDI as chanito said the CV carb is ineffective right? so does that mean our needles no longer gradually pulls up?


My experience with the new needle is it tugs a bit harder on acceleration...but it was rather cold yesterday when i tested it...it couldn't reach 60 in some areas that i did, but in other areas im going faster than I could normally go...


Such mixed and confused results...and today is snowing Im depressed

It is a common misconception that the needle will pull out totally, it does not, the reason you want a little of the needle still in, is so the needle will not pull out and miss the hole when you release the throttle making for an interesting moment with the carb needle sticking out, so yes the needle is longer in a later model but is also thinner so at full throttle it will allow more gas than a thicker one, however i think that the shorther one aloows a better atomization at full throttle as the gas leave the jet faster. actually of all the carb modifications and adjusments, the needle should be the last.