Another, Air Intake + Jets = ???

That is a very interesting angle on the reason for the scavenging pipe location, i doubt the vacuum is strong enough to help the valves close, but maybe there is an aerodynamic advantage under lower than atmospheric pressure, the reason you want that line dumping the blow-by gases is that you want to burn them as gases, so the closer to the throttle the better, as if those gases are allow to cool and become liquid the are harder to burn.
The reason why is not a good idea to use a filter at the carb mouth, is the the CV (constant vacuum in my old books, constant velocity on the new ones ) requires a calm air supply so the piston can slide smooth, a filter that close allows the air at the intake of the carb to create some very unstable conditions for the piston to slide smooth so it creates a very weird acting carburetor I sure love the look of the filter right there though

I saw this thread last night but I didn't respond because you've started a great, but complicated discussion and I figured this response might take me a while.

First, about the hose that supposedly needs the side draft, I believe we are talking about the hose that goes from the of the valve cover at the front of our engines. (Just as background info for others reading, this hose is the exit hose for the air from inside our engine case that comes in through the new PCV system for 06/07.) It was my understanding that the reason we want this plugged into the intake is so the gases containing oil and gas fumes can be burnt. It seems the the side draft may help to suck more air through this hose and make the PCV system work better. It's also possible that the valve closing idea you presented is true although I suspect it's more of a 'good idea' that an absolute requirement. Regardless, it is a good idea to have this hose pugged into the main filter.

With all that said, I don't see this hose plugged into your main filter...what's the deal with that? I had mine plugged into my Pod filter from Battlescooter but my pod filter broke and the filter part fell off and was lost so now I have a sexy K&N filter on there that I really should take a pic of sometime. My plan is to cut a small hole in the rubber intake hose kinda close to the carb and super-glue a little nipple in there to mount the PCV hose too so that it has that side draft and so it is close to the carb like Chanito recommended (so the fumes stay vapourized). Okay I think that's all I have to say on the crankcase ventilation hose.

Next, I'll discuss the whole 'opened up airbox' vs. K&N style filter issue. My experience with opening up the airbox has been that it increases your airflow at low RPMs so you're lean there but on the top end it doesn't do that much because other bottlenecks like our cam don't allow for more flow. With that said, when you install an opened up airbox cover you want just a wee little bit more gas on the top end but a lot more on the low end. Now when you go to a larger main jet, that isn't really open at low speeds so you need to go way bigger than needed on the top end just to get it adequate on the low end. The solution of course is a bigger slow jet but you need to be careful here too because slow jets are always open so they're make you richer across the board so even just doing the slow jet can make you too rich up top. As an aside, if you work out the math, increasing your slow jet 2 sizes (ie. 35 to a 40) gives you a fuel increase on the TOP END that's about the same as increasing the main jet one size. This is because adding 0.02mm in diameter adds a lot more area when it's 75 going to 77 than it does from 35 going to 37.

Okay so if you do the opened up airbox you need just a little more gas for the top end but a lot more for the low end. If you were to just switch your main jet to a 77 from a 75 you'd probably run good on the top but you'd never get there because it would run so poorly up to 35mph that you wouldn't get above 10mph unless you bombed a hill or covered part of the intake to reduce your air intake. As a result, back in the day when slow jets weren't available, most people would wind up with an 85 or 90 main jet which was way rich up top and hurting there top end but it provided enough gas on the low end to provide adequate performance. Now that slow jets are available you want to go with a combo something like 42/75 because that will give you a bit more gas on the top end, similar to a 79 or so main jet alone and quite a bit more gas on the low end. This might be hair rich up top but it's a pretty good guess I think.

With all that said, a pod style filter (on the carb or not) should flow about the same because I don't think the real bottleneck is the filter. I think what you are experiencing is the uneven airflow that Chanito spoke of and that is causing you to not realize that possible airflow benefits much so the stock jetting works fine by chance. I've tried using the exact filter you are using directly on the carb and it ran fine but not awesome like the pod filter on 2/3 of the intake tube did. I totally agree with everyone that having the filter directly on the carb looks awesome but from a performance standpoint it probably isn't the best idea. I think you just lucked out with the jetting and if you put some hose between it in the carb your Ruckus would run even better if you managed to increase the gas just the right amount.

Alright, here is my new set up, and it runs great! for now

The only thing is I still have a backfire after getting out of full throttle, like when I come to a stop after being on it. If I roll of the throttle it lessens the "POP" I even went back to a 72 main....Oh well, it rus good, now where the hell is my Pollini!!!?!?!?!?!





KP

Ok here are some simple instructions, I can take pics later if needed. This is using an '03 style intake tube.

If you look right after the first bend, either direction, you'll see an area about 3.5" long that is mostly flat/straight, I noticed that there is a casting line in the rubber, I cut there with a hacksaw and used a razor blade to clean it up. Now if you try to just bolt the filter on there it won't work well...so what I did was remove the raise sections that run perpendicular to the intake tube with a razor. Then I took the "horn" from the end of the intake tube and cut it off, flipped it around, shoved it on there and bolted the filter on that.

As far as the fresh air for the carb I just drilled a hold in the end of the reverb chamber on the intake tube and shoved it in there. I can say that the scooter runs ok and the weird surging I was noticing is gone.

Thanks, KP