Without a dyno there's probably no such thing as "spot on" jetting. We're all a bit rich or a bit lean even when we think we're right on it.

I'm guessing the difference in flow (snorkel on or off) is very small. But if you're jetting is just a bit rich - then removing the snorkel and getting just that little bit extra airflow may move you in the right direction. Of course, if you're a bit lean - then adding the snorkel may move you a bit in the right direction. Unfoirtunately, I don't have a KDX snorkel to give it a try. Don't know which way it would go. If anyone wants to sell their KDX snorkel...let me know.

My own litmus test is a 50mph sign maybe 120 yards from where I turn onto the main road near my house. I hit it and see what my top speed is at the 50mph sign. Stock, my KLX hit 47 (indicated). With free/cheap/jetted - I can hit 53-54mph at the sign. Doesn't vary with temps in the AM or afternoon now, so I'm close. I tried recently with the lid off and my speed at the sign dropped to just under 50. Sounded badass but didn't produce. I like it better quiet.

BTW, my old KLR could only hit 45. My LC4 hit 65. My husky 610 hit 65, my old Bandit 1200 hit 75 and my Bandit 1250 hits 80.

 

no snorkel was loud and caused lot of vibrations under the saddle....kdx snorkel decreased the noise and reduced the vibrations significantly....maybe i'm associating the quiet smooth engine as the klx running "better", but the kdx snorkel is remaining on...

 

I don't know...I think we can achieve "spot-on" jetting, but realistically it's only at our given operating elevation for the most part. And rather than a dyno, the use of an O2 sensor like toyotabuilder often mentions is probably the best way to attain it. Still, spot-on jetting can be attained with a bit of manual jetting attempts, but it's probably a bit quicker and easier with an O2 sensor setup.

It seems pretty clear from the different responses here that there is more airflow with the airbox lid off. The posts of users who see a difference with the addition or removal of the lid fairly well prove that. It's just that the jetting needs to be aligned with either the lid off or snorkel on depending on your preference. I can see running the snorkel if you don't like the sound of the bike with the lid off.

djchan, your acceleration test is very much like the Mikuni recommendations for final tuning of the main jet segment of the TM36. Of course they're assuming you leave everything else the same so you can choose the best main jet, but the principle of jetting to the speed achieved carries over to finding the best setup for your bike. Your speed would most likely increase with the lid off with the proper jetting to match, as I think you well know, but preferring the sound of the bike with the lid/snorkel on is understandably reasonable.

 

Open airbox CLEARLY flows more air at the upper 1/3 rpm range at or close to full throttle. I do not think it makes much difference at the lower 2/3 rpm especially at smaller throttle openings.

Because of the overlap in the needle and the main jet, I think it makes it harder to tune the carb with the airbox lid off. What may be the perfect main jet at full throttle near redline may be a tad rich for 2/3 throttle at 7000 rpm for example.

 

I thought this thread was a matter of no snorkel vs. KDX , not lid on or off ?

Of course there is more flow without the lid, just look at the opening. But whether or not that translates into increased power i don't think was ever proven with empirical data as far as i know.

again as I stated earlier i didn't feel a bit of difference between the kdx snorkel or just the open snorkel hole besides the intake being louder without the snorkel.

 

Ooops sorry, misread OP's post.

 

wildcard, I mentioned the difference in the original question in my post, but my point is still...why run with the OEM hole in the airbox without a snorkel instead of either making the hole bigger or running with the lid off? I tested this on mine before cutting the hole in the lid. I couldn't tell the difference in noise level once the snorkel was removed vs. open lid. It seems once the sound damping effect of the snorkel is gone, it's got the same tone regardless...annoying to some and not an issue to others...louder yes.

As stated before, no empiral data as such, but when you increase flow in and jet appropriately for that flow, the odds of not getting a power increase are rather small...assuming you have an appropriate exhaust to take advantage also. This is just a basic for most 4-stroke engines. Of course we're not talking about neck-snapping power increases of any kind with "most" of these mods. It is after all still a KLX...LOL!

 

WOW! I'm surprised I got this many replies in the short amount of time. This is exactly why I love this forum and spend most of my free time here .

From the replies I read, I gather it's more of a personal preference when it comes to KDX snorkel vs no snorkel. It could possibly flow a tad bit more air but the intake noise and vibration are a lot more noticeable.

I know the snorkel does not allow water to get in the intake when doing water crossings, but what about riding in the rain? Does the snorkel make a difference there?

 

can't imagine much water getting in while riding in rain...but, i can imagine water getting in if parked in the rain with no snorkel...bike angled and water getting between the saddle and airbox just dripping in....

 

I don't really think there's a vibration issue associated with running with the airbox lid off. If the jetting is way off, maybe there's a roughness in the throttle response or the way it runs that one might feel, but it's probably more akin to the placebo that more noise may translate to more power with some riders...so more noise could also translate to a perceived vibration along with it. I'm not saying that the poster isn't having a vibration, but I'd suspect something else may be going on too.

On the snorkel and water/rain, this is why I cut the hole in the lid bigger rather than just run without it. Without the lid the airbox is more of a big cup with its edges waiting to let water rush in more easily in a water crossing splash. At least that's my take on it.